Where's Zika most likely in the US? The answer may surprise you

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Zika virus is spreading fast across Latin America and the Caribbean, spread by both people and by the Aedes aegypti mosquito. A new study shows where in the U.S. it's most likely to spread, too, and some of the vulnerable cities may be surprising.

New York, Philadelphia and Washington D.C. have a moderate risk, the team at the National Center for Atmospheric Research (NCAR) in Colorado say. That's because the Aedes aegypti mosquitoes can live there and thrive in the hot, humid summers those cities typically enjoy.

Miami, Orlando, Savannah and Charleston are the highest-risk cities — higher even than Houston, the team reports in the Public Library of Science journal PLOS Currents Outbreaks.

Photos related to the Zika virus:

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Where's Zika most likely in the US? The answer may surprise you
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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Low-risk cities include dry, high-altitude places such as Denver, Albuquerque and Salt Lake City, even though they're warm in summer.

Related:Leading US Doctors Urge Funding for Zika Fight

"While there is much we still don't know about the dynamics of Zika virus transmission, understanding where the Aedes aegypti mosquito can survive in the U.S. and how its abundance fluctuates seasonally may help guide mosquito control efforts and public health preparedness," NCAR's Andrew Monaghan, who led the study, said in a statement.

"Even if the virus is transmitted here in the continental U.S., a quick response can reduce its impact," added NCAR scientist Mary Hayden, a medical anthropologist who worked on the study.

Zika virus outbreaks:

Two factors are needed for Zika to spread. A human being has to carry the virus in his or her body and the Aedes aegypti mosquitoes need to be on hand to carry it to others. The virus can also be sexually transmitted, but that results in less spread, the Centers for Disease Control and Prevention says.

Experts almost all agree that Zika is unlikely to spread much in the U.S., in part because the Aedes aegypti mosquito isn't common except in parts of the far south and Hawaii, and also because Americans mostly live indoors, with air conditioning and little chance for the mosquitoes to live and breed inside homes.

They've predicted small, localized outbreaks come summer.

This is based on past history. The CDC and other federal agencies have already said they're looking to see where and how other viruses carried by Aedes mosquitoes spread in the U.S. Those include chikungunya and dengue virus.

Related:Study Finds Zika Damages Babies at All Stages of Pregnancy

Monaghan's team took these factors into account, as well as data on travelers from affected regions that would coincide with the hot summer months when mosquitoes thrive.

"Meteorological conditions are largely unsuitable for Aedes aegypti over the U.S. during winter months (December-March), except in southern Florida and south Texas where comparatively warm conditions can sustain low-to-moderate potential mosquito abundance," Monaghan's team wrote.

CDC says 30 million to 40 million Americans fly to Latin America and the Caribbean every year and even more go by land.

"We chose 50 U.S. cities within and near the known range of Aedes aegypti," Monaghan's team wrote.

"These cities were selected because they may be meteorologically suitable for Aedes aegypti for at least part of the year, though not all have recorded the presence of Aedes aegypti to date."

They also calculated whether people had water in containers handy for the mosquitoes to breed. Aedes mosquitoes can breed in very small containers and are notorious for making their homes in and around where people live.

"There is strong evidence that Aedes aegypti eggs are capable of surviving even in harsh winter conditions as a result of being laid in favorable cryptic environments such as subterranean habitats," the team noted.

"Poverty has been linked to a number of indicators of elevated exposure to mosquitoes such as lower usage rates of air conditioning and less efficient cooling options."

Based on all this, there's not much risk of Aedes-transmitted disease anywhere but south Florida and Texas in winter.

"By mid-July, all 50 cities are meteorologically suitable for Aedes aegypti, with far southeastern cities being suitable for high abundance, and other eastern cities being suitable for moderate-to-high abundance," the team added.

What happens if Zika can be spread by other Aedes mosquitoes, such as Aedes albopictus, aka the Asian tiger mosquito? Then all bets are off — those mosquitoes can survive in much colder climates, the researchers say.

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