WHO: Guillain-Barre on rise in 5 Latam countries, no proven link to Zika

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WHO Expected to Release Info on Zika Link to Birth Defects

GENEVA, Feb 13 (Reuters) - A neurological disorder suspected of links to the mosquito-borne Zika virus is on the rise in Brazil, Colombia, El Salvador, Suriname and Venezuela, the World Health Organization (WHO) said on Saturday.

The rare Guillain-Barre syndrome, in which the body's immune system attacks part of the nervous system, causes gradual weakness in the legs, arms and upper body and sometimes leads to total paralysis.

SEE ALSO: WHO expects to set link between Zika and microcephaly in weeks, vaccine 18 months

"In the context of the Zika virus outbreak, Brazil, Colombia, El Salvador, Suriname and Venezuela have reported an increase of GBS (Guillain-Barre Syndrome)," the WHO said in a weekly report on Zika virus now circulating in 34 countries, including 26 in the Americas.

"The cause of the increase in GBS incidence observed in Brazil, Colombia, El Salvador and Suriname remains unknown, especially as dengue, chikungunya and Zika virus have all been circulating simultaneously in the Americas," it added.

Photos of the Zika outbreak:

35 PHOTOS
Zika, Mosquito borne illness causing birth defects in Brazil
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WHO: Guillain-Barre on rise in 5 Latam countries, no proven link to Zika
In this Jan. 29, 2016 photo, Tainara Lourenco, who is five months pregnant, sits inside her house at a slum in Recife, Brazil. Like many of the estimated 400,000 women currently pregnant in Brazil, she canât afford mosquito repellent. The government has pledged to start providing repellent to low-income women and promises to deploy the Armed Forces to help eliminate Aedesâ breeding places. (AP Photo/Felipe Dana)
RECIFE, BRAZIL - JANUARY 29: Dr. Valeria Barros treats a 6-week old baby born with microcephaly at the Lessa de Andrade polyclinic during a physical therapy session on January 29, 2016 in Recife, Pernambuco state, Brazil. Health officials believe as many as 100,000 people have been exposed to the Zika virus in Recife, although most never develop symptoms. In the last four months, authorities have recorded around 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 31: Alice Vitoria Gomes Bezerra, 3-months-old, who has microcephaly, is held by her mother Nadja Cristina Gomes Bezerra on January 31, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 29: David Henrique Ferreira, 5 months, who was born with microcephaly, is kissed by his mother Mylene Helena Ferreira on January 29, 2016 in Recife, Pernambuco state, Brazil. In the last four months, authorities have recorded around 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 29: David Henrique Ferreira, 5 months, who was born with microcephaly, is held by his grandmother Maria Elisabeth as his mother stands at right on January 29, 2016 in Recife, Pernambuco state, Brazil. In the last four months, authorities have recorded around 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. (Photo by Mario Tama/Getty Images)
Pregnant woman Angelica Prato, infected by the Zika virus, is attended at the Erasmo Meoz University Hospital in Cucuta, Colombia, on January 25, 2016. Authorities in Brazil, Colombia, Ecuador, El Salvador and Jamaica have advised couples to avoid pregnancy for the time being due to the presence of the Zika virus because if a pregnant woman is infected by the virus, the baby could be born with microcephaly. The Zika virus, a mosquito-borne disease suspected of causing serious birth defects, is expected to spread to all countries in the Americas except Canada and Chile, the World Health Organization said. AFP PHOTO/Schneyder Mendoza / AFP / SCHNEYDER MENDOZA (Photo credit should read SCHNEYDER MENDOZA/AFP/Getty Images)
In this Jan. 29, 2016 photo, Tainara Lourenco smiles as she chats with neighbors from the entrance of home at a slum in Recife, Brazil. Unemployed and five months pregnant, 21-year-old Lourenco lives in a slum at the epicenter of Brazilâs tandem Zika and microcephaly outbreaks, the state of Pernambuco. (AP Photo/Felipe Dana)
RECIFE, BRAZIL - JANUARY 27: Alice Vitoria Gomes Bezerra, 3-months-old, who has microcephaly, is placed in her crib by her father Joao Batista Bezerra on January 27, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. At least twelve cases in the United States have now been confirmed by the CDC. (Photo by Mario Tama/Getty Images)
Gleyse Kelly da Silva holds her daughter Maria Giovanna as she sleeps in their house in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. Brazilian officials still say they believe there's a sharp increase in cases of microcephaly and strongly suspect the Zika virus, which first appeared in the country last year, is to blame. The concern is strong enough that the U.S. Centers for Disease Control and Prevention this month warned pregnant women to reconsider visits to areas where Zika is present. (AP Photo/Felipe Dana)
Kleisse Marcelina ,24, bathes her son Pietro, 2 month, suffering from microcephalia caught through an Aedes Aegypti mosquito bite, in Salvador, Brazil on January 28 , 2016. AFP PHOTO / Christophe SIMON / AFP / CHRISTOPHE SIMON (Photo credit should read CHRISTOPHE SIMON/AFP/Getty Images)
RECIFE, BRAZIL - JANUARY 26: Grandmother Ivalda Caetano holds Ludmilla Hadassa Dias de Vasconcelos (2 months), who has microcephaly, at Oswald Cruz hospital on January 26, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. At least twelve cases in the United States have now been confirmed by the CDC. The Brazilian government announced it will deploy more than 200,000 troops to combat the mosquitos which are spreading the Zika virus. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 27: Dr. Vanessa Van Der Linden, the neuro-pediatrician who first recognized and alerted authorities over the microcephaly crisis in Brazil, measures the head of a 2-month-old baby with microcephaly on January 27, 2016 in Recife, Brazil. The baby's mother was diagnosed with having the Zika virus during her pregnancy. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. At least twelve cases in the United States have now been confirmed by the CDC. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 31: Alice Vitoria Gomes Bezerra, 3-months-old, who has microcephaly, is held by her mother Nadja Cristina Gomes Bezerra on January 31, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout nearly all the Americas. (Photo by Mario Tama/Getty Images)
Physical therapist Isana Santana treats Ruan Hentique dos Santos, suffering from microcephalia caught through an Aedes Aegypti mosquito bite, at Obras Socias irma dulce hospital in Salvador, Brazil on January 28 , 2016. AFP PHOTO / Christophe SIMON / AFP / CHRISTOPHE SIMON (Photo credit should read CHRISTOPHE SIMON/AFP/Getty Images)
The parents of Icaro Luis , 2 month, suffering from microcephalia caught through an Aedes Aegypti mosquito bite, Physical therapist Isana Santan at the Obras socias irma dulce hospital in Salvador, Brazil on January 28, 2016. AFP PHOTO / Christophe SIMON / AFP / CHRISTOPHE SIMON (Photo credit should read CHRISTOPHE SIMON/AFP/Getty Images)
Physical therapist Isana Santana treats Ruan Hentique dos Santos, suffering from microcephalia caught through an Aedes Aegypti mosquito bite, at Obras Socias irma dulce hospital in Salvador, Brazil on January 28 , 2016. AFP PHOTO / Christophe SIMON / AFP / CHRISTOPHE SIMON (Photo credit should read CHRISTOPHE SIMON/AFP/Getty Images)
Ana Paula Santos, 34, holds her 45-day-old daughter Flavia Alessandra suffering from microcephalia supposedly caught through an Aedes aegypti mosquito bite, at the Obras Sociais Irma Dulce hospital in Salvador, Brazil on January 27, 2016. AFP PHOTO / Christophe SIMON / AFP / CHRISTOPHE SIMON (Photo credit should read CHRISTOPHE SIMON/AFP/Getty Images)
RECIFE, BRAZIL - JANUARY 25: Estafany Perreira holds her nephew David Henrique Ferreira, 5 months, who has microcephaly, on January 25, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. Microcephaly results in newborns with abnormally small heads and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to further spread in South, Central and North America. At least twelve cases of Zika in the United States have now been confirmed by the CDC. (Photo by Mario Tama/Getty Images)
RECIFE, BRAZIL - JANUARY 25: Mother Mylene Helena Ferreira cares for her son David Henrique Ferreira, 5 months, who has microcephaly, on January 25, 2016 in Recife, Brazil. In the last four months, authorities have recorded close to 4,000 cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. Microcephaly results in newborns with abnormally small heads and is associated with various disorders including decreased brain development. According to the World Health Organization (WHO), the Zika virus outbreak is likely to further spread in South, Central and North America. At least twelve cases of Zika in the United States have now been confirmed by the CDC. (Photo by Mario Tama/Getty Images)
In this Dec. 23, 2015 photo, Solange Ferreira bathes her son Jose Wesley in a bucket at their house in Poco Fundo, Pernambuco state, Brazil. Ferreira says her son enjoys being in the water, she places him in the bucket several times a day to calm him. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, 10-year-old Elison nurses his 2-month-old brother Jose Wesley at their house in Poco Fundo, Pernambuco state, Brazil. Suspicion of the link between microcephaly and the Zika virus arose after officials recorded 17 cases of central nervous system malformations among fetuses and newborns after a Zika outbreak began last year in French Polynesia, according to the European Center for Disease Prevention and Control. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, plastic bags and trash lay on the ground in Santa Cruz do Capibaribe, where many cases of Zika where reported in Pernambuco state, Brazil, Wednesday. The Zika virus, first detected about 40 years ago in Uganda, has long seen as a less-painful cousin to dengue and chikunguya, which are spread by the same Aedes mosquito. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, 10-year-old Elison, left, watches as his mother Solange Ferreira bathes Jose Wesley in a bucket at their house in Poco Fundo, Pernambuco state, Brazil. Ferreira says Jose Wesley enjoys being in the water, she places him in the bucket several times a day to calm him. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, Dejailson Arruda holds his daughter Luiza at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. More than 2,700 babies have been born in Brazil with microcephaly this year, up from fewer than 150 in 2014. Brazilâs health officials say theyâre convinced the jump is linked to a sudden outbreak of the Zika virus that infected Pereira, though international experts caution itâs far too early to be sure. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, 10-year-old Elison carries his 2-month-old brother Jose Wesley at their house in Poco Fundo, Pernambuco state, Brazil. More than 2,700 babies have been born in Brazil with microcephaly this year, up from fewer than 150 in 2014. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, Jose Wesley sleeps covered by a mosquito net in Poco Fundo, Pernambuco state, Brazil. Jose Wesleyâs mother Solange Ferreira had never heard of microcephaly before her youngest son was diagnosed a couple of days after his birth. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, 5-year-old Elenilson, left, holds a notebook as he plays next to his 2-month-old brother Jose Wesley at their house in Poco Fundo, Pernambuco state, Brazil. Their mother, Solange Ferreira had never heard of microcephaly before her youngest son was diagnosed a couple of days after his birth. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Angelica Pereira applies perfume on Luiza as her father Dejailson Arruda holds her at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. While thereâs never before been a detected link between the virus and microcephaly, âthere has never been an epidemic of Zika in the proportions that we are looking at now in Brazil,â said Pedro Fernando Vasconcelos, a researcher at Evandro Chagas Institute investigating an association between the virus and the birth defects. (AP Photo/Felipe Dana)
In this Dec. 23, 2015 photo, Dejailson Arruda holds his daughter Luiza at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. Luiza was born in October with a rare condition, known as microcephaly. Luiza's mother Angelica Pereira was infected with the Zika virus after a mosquito bite. Brazilian health authorities are convinced that Luiza's condition is related to the Zika virus that infected her mother during pregnancy. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Angelica Pereira holds Luiza outside their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. Luiza was born in October with a rare condition, known as microcephaly. The Zika virus, first detected in humans about 40 years ago in Uganda, has long seen as a less-painful cousin to dengue and chikunguya, which are spread by the same Aedes mosquito. Until a few months ago, investigators had no reported evidence it might be related to microcephaly. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Angelica Pereira, right, holds her daughter Luiza as she waits for their appointment with a neurologist at the Mestre Vitalino Hospital in Caruaru, Pernambuco state, Brazil. In November, Brazilian researchers detected the Zika virus genome in amniotic fluid samples from two women whose fetuses were been diagnosed with microcephaly by ultrasound exams, the Pan American Health Organization reported. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Luiza has her head measured by a neurologist at the Mestre Vitalino Hospital in Caruaru, Pernambuco state, Brazil. Luiza was born in October with a head that was just 11.4 inches (29 centimeters) in diameter, more than an inch (3 centimeters) below the range defined as healthy by doctors. Her rare condition, known as microcephaly, often results in mental retardation. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Angelica Pereira holds her daughter Luiza as she waits for her husband at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. In the early weeks of Angelica Pereiraâs pregnancy, a mosquito bite began bothering her. At first it seemed a small thing. But the next day she awoke with a rash all over her body, a headache, a fever and a burning in her eyes. The symptoms disappeared within four days, but she fears the virus has left lasting consequences. (AP Photo/Felipe Dana)
In this Dec. 22, 2015 photo, Dejailson Arruda holds his daughter Luiza at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil. Luiza was born in October with a head that was just 11.4 inches (29 centimeters) in diameter, more than an inch (3 centimeters) below the range defined as healthy by doctors. Her rare condition, known as microcephaly, often results in mental retardation. (AP Photo/Felipe Dana)
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Investigations continue to determine the cause, WHO said, noting that there was no laboratory confirmation of Zika virus in patients with GBS in Colombia and El Salvador.

Venezuela has reported 252 cases of Guillain-Barre occurring at the same time and place as Zika infections, it said. "Zika virus infection was confirmed for three of the GBS cases, including one fatal case."

Venezuela's President Nicolas Maduro said on Thursday that three people had died of complications linked to Zika virus and that suspected cases of Zika had risen to 5,221.

Even in the best of settings, 3 to 5 percent of Guillain-Barre patients die from complications, which can include paralysis of the muscles that control breathing, blood infection, lung clots or cardiac arrest, according to the WHO.

In French Polynesia, all 42 GBS cases identified during the Zika virus outbreak in 2013-2014 tested positive for dengue and Zika virus infection, the WHO said.

Efforts to combat Zika include genetically engineered mosquitos:

21 PHOTOS
Genetically engineered mosquitoes to combat Zika
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WHO: Guillain-Barre on rise in 5 Latam countries, no proven link to Zika
PIRACABA, BRAZIL - FEBRUARY 11 :A Biologist releases genetically modified mosquitoes in the city on February 11, 2016 in Piracicaba, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A biologist works on putting blood on iron plates to feed the females of the nursery that produces genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A biologist works on putting blood on iron plates to feed the females of the nursery that produces genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
PIRACABA, BRAZIL - FEBRUARY 11 :A Biologist releases genetically modified mosquitoes in the city on February 11, 2016 in Piracicaba, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
PIRACABA, BRAZIL - FEBRUARY 11 :A Biologist releases genetically modified mosquitoes in the city on February 11, 2016 in Piracicaba, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
SAO PAULO, BRAZIL - FEBRUARY 11: The Oxitec laboratory located in Campinas, 100km from Sao Paulo, is producing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer on February 11, 2016 in Campinas, Brazil. Campinas Daily are released 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito. These mosquitoes compete with wild mosquitoes and win the battle because they were outnumbered. After the breeding season, the natural females lay eggs that are not genetically modified Zika virus transmitters. (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
PIRACABA, BRAZIL - FEBRUARY 11 :A Biologist releases genetically modified mosquitoes in the city on February 11, 2016 in Piracicaba, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified male mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified male mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist works with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
CAMPINAS, BRAZIL - FEBRUARY 11: A Biologist work with genetically modified mosquitoes on February 11, 2016 in Campinas, Brazil. Technicians from the Oxitec laboratory located in Campinas, 100km from Sao Paulo, are releasing genetically modified mosquitoes Aedes Egypti to combat Zika virus. The laboratory is acting in Piracicaba who had a dengue outbreak last summer with 132 cases and after treatment showed only two cases this summer .The Lab will release 250,000 genetically modified mosquitoes in two neighborhoods with a large concentration of incident cases of egypti aedes mosquito, the modified mosquitoes compete with wild mosquitoes and replace them with non-Zika transmitting mosquitoes . (Photos by Victor Moriyama/Getty Images)
SANTO DOMINGO, DOMINICAN REPUBLIC - FEBRUARY 10: Yira Paulino, an entomologist, works with Aedes aegypti mosquitoes that carry the Zika virus at a laboratory of the National Center for the Control of Tropical Diseases (CENCET) in Santo Domingo, Dominican Republic on February 10, 2016. (Photo by Stringer /Anadolu Agency/Getty Images)
SANTO DOMINGO, DOMINICAN REPUBLIC - FEBRUARY 10: Aedes aegypti mosquitoes that carry the Zika virus are seen at a laboratory of the National Center for the Control of Tropical Diseases (CENCET) in Santo Domingo, Dominican Republic on February 10, 2016. (Photo by Stringer /Anadolu Agency/Getty Images)
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There is no proven link between the Zika virus, the birth defect microcephaly and Guillain-Barre syndrome, but senior WHO expert Marie-Paule Kieny said on Friday that scientists suspected on and might be able to confirm it within weeks.

Microcephaly is a condition marked by a baby's abnormally small head size, which can result in developmental problems.

"Prevention measures have become critical. There are concerns that the Zika virus may spread globally to environments where mosquitoes can live and breed," the WHO said on Saturday.

Brazil is investigating the potential link between Zika infections and more than 4,300 suspected cases of microcephaly.

Researchers have confirmed more than 460 of these cases as microcephaly and identified evidence of Zika infection in 41 of these cases, but have not proven Zika can cause microcephaly.

Pregnant women should consider putting off travel to areas infected with the Zika virus as a precautionary measure, the WHO said on Friday.

"Brazil will not stand down from hosting the 2016 Olympic Games in Rio. The risk of contracting the Zika virus is minimal in August, the height of winter in the region and a time of year when mosquitoes are least active," WHO said on Saturday, citing remarks made by member states at a private briefing last week.

Zika virus in South America:

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Zika, health agents trying to eradicate Zika mosquitoes in South America, Central America
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WHO: Guillain-Barre on rise in 5 Latam countries, no proven link to Zika
An Aedes aegypti mosquito is photographed through a microscope at the Fiocruz institute in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. The mosquito is a vector for the proliferation of the Zika virus currently spreading throughout Latin America. New figures from Brazil's Health Ministry show that the Zika virus outbreak has not caused as many confirmed cases of a rare brain defect as first feared. (AP Photo/Felipe Dana)
A Sucre municipal worker fumigates for Aedes aegypti mosquitoes that transmit the Zika virus in the Petare neighborhood of Caracas, Venezuela, Monday, Feb. 1, 2016. Venezuela is reporting a jump in cases of a rare, sometimes paralyzing syndrome that may be linked to the Zika virus. (AP Photo/Fernando Llano)
In this Wednesday, Jan. 27, 2016 photo, Aedes aegypti mosquitoes sit in a petri dish at the Fiocruz institute in Recife, Pernambuco state, Brazil. The mosquito is a vector for the proliferation of the Zika virus spreading throughout Latin America. New figures from Brazil's Health Ministry show that the Zika virus outbreak has not caused as many confirmed cases of a rare brain defect as first feared. (AP Photo/Felipe Dana)
RECIFE, BRAZIL - FEBRUARY 01: David Henrique Ferreira, 5 months, who was born with microcephaly, is examined by a doctor on February 1, 2016 in Recife, Pernambuco state, Brazil. Ferreira's mother says she spends up to eight hours per day in transit on buses, three days per week, to visit a litany of doctors with David. In the last four months, authorities have recorded thousands of cases in Brazil in which the mosquito-borne Zika virus may have led to microcephaly in infants. The ailment results in an abnormally small head in newborns and is associated with various disorders including decreased brain development. The World Health Organization (WHO) declared the Zika virus a 'public health emergency of international concern' today. (Photo by Mario Tama/Getty Images)
Health ministry personnel fumigate a classroom against the Aedes aegypti mosquito, vector of the dengue, Chikungunya and Zika viruses in Tegucigalpa, , on February 1, 2016. Honduran President Juan Orlando Hernandez on Friday declared the country on a preventive state of alert due to the Zika virus which in the last 44 days killed a person and infected some 1000. AFP PHOTO/Orlando SIERRA. / AFP / ORLANDO SIERRA (Photo credit should read ORLANDO SIERRA/AFP/Getty Images)
In this Thursday, Jan. 28, 2016 photo, Daniele Ferreira dos Santos holds her son Juan Pedro as he undergoes visual exams at the Altino Ventura foundation in Recife, Pernambuco state, Brazil. Santos was never diagnosed with Zika, but she blames the virus for her sonâs defect and for the terrible toll it has taken on her life. (AP Photo/Felipe Dana)
A man works on a fence amidst a cloud of insecticide as city workers fumigate to combat the Aedes Aegypti mosquitoes that transmits the Zika virus, at the San Judas Community in San Salvador, El Salvador, Tuesday, Jan. 26, 2016. Worries about the rapid spread of Zika through the hemisphere has prompted officials in El Salvador, Colombia and Brazil to suggest women stop getting pregnant until the crisis has passed. (AP Photo/Salvador Melendez)
A health worker stands in the Sambadrome as he sprays insecticide to combat the Aedes aegypti mosquitoes that transmits the Zika virus in Rio de Janeiro, Brazil, Tuesday, Jan. 26, 2016. Inspectors begin to spray insecticide around Sambadrome, the outdoor grounds where thousands of dancers and musicians will parade during the city's Feb. 5-10 Carnival celebrations. Brazil's health minister says the country will mobilize some 220,000 troops to battle the mosquito blamed for spreading a virus linked to birth defects. (AP Photo/Leo Correa)
Carmen Chicas Mejia, 82, covers her mouth and nose while city workers fumigate her home to combat the Aedes Aegypti mosquitoes that transmit the Zika virus, at the San Judas Community in San Salvador, El Salvador, Tuesday, Jan. 26, 2016. Worries about the rapid spread of Zika through the hemisphere has prompted officials in El Salvador, Colombia and Brazil to suggest women stop getting pregnant until the crisis has passed. (AP Photo/Salvador Melendez)
Dead insects and larvae float in an empty vase at a cemetery in Cartagena, Colombia, Tuesday, Jan. 26, 2016. Local health workers emptied vases during a campaign to destroy potential hatcheries of Aedes aegypti mosquitoes that transmits the Zika virus at a the cemetery as part of a prevention campaign that according to the health ministry has already infected more than 16,000 people in Colombia, and could hit more than half a million. (AP Photo/Reinaldo Reyes)
A woman covers her mouth while city workers fumigate insecticide to help combat the Aedes Aegypti mosquitoes that transmit the Zika virus, at the San Judas Community in San Salvador, El Salvador, Tuesday, Jan. 26, 2016. Worries about the rapid spread of Zika through the hemisphere has prompted officials in El Salvador, Colombia and Brazil to suggest women stop getting pregnant until the crisis has passed. (AP Photo/Salvador Melendez)
A health worker stands in the Sambadrome as he sprays insecticide to combat the Aedes aegypti mosquitoes that transmit the Zika virus, in Rio de Janeiro, Brazil, Tuesday, Jan. 26, 2016. Inspectors began to spray insecticide around the Sambadrome, the outdoor grounds where thousands of dancers and musicians will parade during the city's Feb. 5-10 Carnival celebrations. Brazil's health minister says the country will mobilize some 220,000 troops to battle the mosquito blamed for spreading a virus linked to birth defects. (AP Photo/Leo Correa)
Members of the Migente foundation check mosquito traps in the Paris neighborhood, Bello municipality, Antioquia department, Colombia on January 26, 2016. The Study and Control of Tropical Diseases Program (PECET) of Antioquia's University released one year ago Aedes aegypti mosquitos carrying the Wolbachia pipientis bacteria, which prevents them from transmitting the Zika and dengue viruses, as part of project to fight dengue. The Zika virus, a mosquito-borne disease suspected of causing serious birth defects, is expected to spread to all countries in the Americas except Canada and Chile, the World Health Organization said. AFP PHOTO /Raul ARBOLEDA / AFP / -- / RAUL ARBOLEDA (Photo credit should read RAUL ARBOLEDA/AFP/Getty Images)
A photographer walks through the fumes as Health Ministry employee fumigate against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango, six km east of San Salvador, on January 21, 2016. Health authorities have issued a national alert against the Aedes Aegypti mosquito, because of the link between the Zika virus and microcephaly and Guillain-Barré Syndrome in fetuses. AFP PHOTO/Marvin RECINOS / AFP / Marvin RECINOS (Photo credit should read MARVIN RECINOS/AFP/Getty Images)
Army soldiers check for Aedes aegypti mosquito larvae during a clean-up operation against the insect, which transmits the Zika virus, in Sao Paulo, Brazil on January 22, 2016. AFP PHOTO/Miguel SCHINCARIOL / AFP / Miguel Schincariol (Photo credit should read MIGUEL SCHINCARIOL/AFP/Getty Images)
Army soldiers check for Aedes aegypti mosquito larvae during a clean-up operation against the insect, which transmits the Zika virus, in Sao Paulo, Brazil on January 22, 2016. AFP PHOTO/Miguel SCHINCARIOL / AFP / Miguel Schincariol (Photo credit should read MIGUEL SCHINCARIOL/AFP/Getty Images)
Army soldiers check for Aedes aegypti mosquito larvae during a clean-up operation against the insect, which transmits the Zika virus, in Sao Paulo, Brazil on January 22, 2016. AFP PHOTO/Miguel SCHINCARIOL / AFP / Miguel Schincariol (Photo credit should read MIGUEL SCHINCARIOL/AFP/Getty Images)
A health agent from the Sao Paulo secretariat of public health and army soldiers check for Aedes aegypti mosquito larvae during a clean-up operation against the insect, which transmits the Zika virus, in Sao Paulo, Brazil on January 22, 2016. AFP PHOTO/Miguel SCHINCARIOL / AFP / Miguel Schincariol (Photo credit should read MIGUEL SCHINCARIOL/AFP/Getty Images)
A Health Ministry employee fumigates a home against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango, six km east of San Salvador, on January 21, 2016. Health authorities have issued a national alert against the Aedes Aegypti mosquito, because of the link between the Zika virus and microcephaly and Guillain-Barré Syndrome in fetuses. AFP PHOTO/Marvin RECINOS / AFP / Marvin RECINOS (Photo credit should read MARVIN RECINOS/AFP/Getty Images)
A Health Ministry employee fumigates a home against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango, six km east of San Salvador, on January 21, 2016. Health authorities have issued a national alert against the Aedes Aegypti mosquito, because of the link between the Zika virus and microcephaly and Guillain-Barré Syndrome in fetuses. AFP PHOTO/Marvin RECINOS / AFP / Marvin RECINOS (Photo credit should read MARVIN RECINOS/AFP/Getty Images)
TOPSHOT - A Health Ministry employee fumigates a home against the Aedes aegypti mosquito to prevent the spread of the Zika virus in Soyapango, six km east of San Salvador, on January 21, 2016. Health authorities have issued a national alert against the Aedes Aegypti mosquito, because of the link between the Zika virus and microcephaly and Guillain-Barré Syndrome in fetuses. AFP PHOTO/Marvin RECINOS / AFP / Marvin RECINOS (Photo credit should read MARVIN RECINOS/AFP/Getty Images)
Health ministry employees spray to eliminate breeding sites of the Aedes Aegypti mosquito, which transmits diseases such as the dengue, chicunguna and Zica viruses, in a Tegucigalpa cemetery on January 21, 2016. The medical school at the National Autonomous University of Honduras (UNAH) recommended that women in the country avoid getting pregnant for the time being due to the presence of the Zika virus. If a pregnant woman is infected by the virus, the baby could be born with microcephaly. AFP PHOTO/Orlando SIERRA / AFP / ORLANDO SIERRA (Photo credit should read ORLANDO SIERRA/AFP/Getty Images)
A specialist fumigates the Nueva Esperanza graveyard in the outskirts of Lima on January 15, 2016. Health officials fumigated the largest cementery in Peru and second largest in the world to prevent Chikunguya and Zika virus, which affect several South American countries. AFP PHOTO/ERNESTO BENAVIDES / AFP / ERNESTO BENAVIDES (Photo credit should read ERNESTO BENAVIDES/AFP/Getty Images)
View of the Nueva Esperanza graveyard as it is fumigated in the outskirts of Lima on January 15, 2016. Health officials fumigated the largest cemetery in Peru and second largest in the world to prevent Chikunguya and Zika virus, which affect several South American countries. AFP PHOTO/ERNESTO BENAVIDES / AFP / ERNESTO BENAVIDES (Photo credit should read ERNESTO BENAVIDES/AFP/Getty Images)
A pregnant woman is attended at the Maternal and Children's Hospital in Tegucigalpa on January 21, 2016. The medical school at the National Autonomous University of Honduras (UNAH) recommended that women in the country avoid getting pregnant for the time being due to the presence of the Zika virus. If a pregnant woman is infected by the virus, the baby could be born with microcephaly. AFP PHOTO/Orlando SIERRA / AFP / ORLANDO SIERRA (Photo credit should read ORLANDO SIERRA/AFP/Getty Images)
A pregnant woman waits to be attended at the Maternal and Children's Hospital in Tegucigalpa on January 21, 2016. The medical school at the National Autonomous University of Honduras (UNAH) recommended that women in the country avoid getting pregnant for the time being due to the presence of the Zika virus. If a pregnant woman is infected by the virus, the baby could be born with microcephaly. AFP PHOTO/Orlando SIERRA / AFP / ORLANDO SIERRA (Photo credit should read ORLANDO SIERRA/AFP/Getty Images)
Aedes aegypti mosquito larvae sit in a petri dish at the Fiocruz institute in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. The mosquito is a vector for the proliferation of the Zika virus currently spreading throughout Latin America. New figures from Brazil's Health Ministry show that the Zika virus outbreak has not caused as many confirmed cases of a rare brain defect as first feared. (AP Photo/Felipe Dana)
A technician of the Fiocruz institue stores Aedes aegypti mosquitoes to be used in research, in Recife, Pernambuco state, Brazil, Wednesday, Jan. 27, 2016. The mosquito is a vector for the proliferation of the Zika virus currently spreading throughout Latin America. New figures from Brazil's Health Ministry show that the Zika virus outbreak has not caused as many confirmed cases of a rare brain defect as first feared. (AP Photo/Felipe Dana)
CORRECTS CDC IS INVESTIGATING WHETHER AEDES ALBOPICTUS SPREADS THE ZIKA VIRUS, NOT DEFINITIVE - This 2003 photo provided by the Centers for Disease Control and Prevention shows a female Aedes albopictus mosquito acquiring a blood meal from a human host. On Friday, Jan. 15, 2016, U.S. health officials are telling pregnant women to avoid travel to Latin America and Caribbean countries with outbreaks of a tropical illness linked to birth defects. The Zika virus is spread through mosquito bites from Aedes aegypti and the CDC is investigating whether it is also spread by Aedes albopictus. The disease causes only a mild illness in most people. But thereâs been mounting evidence linking the virus to a surge of a rare birth defect in Brazil. (James Gathany/Centers for Disease Control and Prevention via AP)
Aedes aegypti mosquitos are seen in containers at a lab of the Institute of Biomedical Sciences of the Sao Paulo University, on January 8, 2016 in Sao Paulo, Brazil. Researchers at the Pasteur Institute in Dakar, Senegal are in Brazil to train local researchers to combat the Zika virus epidemic. / AFP / NELSON ALMEIDA (Photo credit should read NELSON ALMEIDA/AFP/Getty Images)
Aedes aegypti mosquitos are seen in containers at a lab of the Institute of Biomedical Sciences of the Sao Paulo University, on January 8, 2016 in Sao Paulo, Brazil. Researchers at the Pasteur Institute in Dakar, Senegal are in Brazil to train local researchers to combat the Zika virus epidemic. / AFP / NELSON ALMEIDA (Photo credit should read NELSON ALMEIDA/AFP/Getty Images)
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