As the number of birth defects linked to a mosquito-borne virus surpasses 4,000 in Brazil, and scientists scramble to create a vaccine to protect against the untreatable disease, public health officials are bracing themselves for a potential outbreak in the United States.

The threat has some advocacy groups pushing for tighter health screenings among travelers and immigrants from Zika-afflicted countries, while public health officials and tropical disease experts argue preparing to fight the Aedes aegypti, an insect that doesn’t respond to common pesticide, is more pressing.

“First of all, I think Zika will come to America, and actually I think it may be more important than the messaging we’re getting out of Washington and [The Centers for Disease Control and Prevention],” Dr. Peter J. Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine, told

Fighting Zika may be tougher in the US than in Latin America

The Aedes aegypti— the primary vector for Zika— ravaged parts of Central and South America by infecting thousands with dengue fever and yellow fever between the ‘40s and ‘60s. But in recent years, it has struck the region again after governments discontinued a reduction effort that involved spraying the controversial insecticide DDT to eradicate the pest. In most places, DDT has been banned after scientists discovered its chemicals can cause environmental wreckage, as well as vomiting, tremors and seizures among humans, as well as other life-threatening side effects.

Joe Conlon, a technical adviser at the American Mosquito Control Association, said the U.S. government would never deploy DDT for precisely those reasons. 

“[DDT]’s got too much emotional baggage and environmental baggage associated with it,” Conlon told “Anyone who would try to use it would be excoriated. We have other means to get rid of these mosquitoes.”

Hotez thinks Washington’s take on the current Zika virus outbreak in Latin America may be a matter of nuance, but that he takes issue with the implication of the term “small outbreak,” which the federal government has said the U.S. could see some of among Gulf Coast states.

“Zika has the ability to cause birth defects,” Hotez said. “By saying ‘small outbreaks’ are going to affect Florida and Texas, are we saying we can tolerate small outbreaks of microcephaly in these states? I would say, ‘No, we don’t have any tolerance.’”

Microcephaly, a condition that causes babies to be born with partially formed brains and abnormally small heads, has been linked to Zika and has impacted nearly 4,100 children in Brazil. In the U.S., which has reported two Zika cases that may have been sexually transmitted, at least one child, in Hawaii, has been born with microcephaly after his or her mother traveled to a Zika-afflicted country. The CDC has advised pregnant women against traveling to more than two dozen regions in the Americas, Oceania and Africa, but it has said more evidence is needed to confirm a link between the virus and microcephaly. 

Hotez said conditions in many of the lower-income areas in the South mimic those of Brazil and other places that have seen a Zika outbreak. Aedes aegypti mosquitoes like to breed in pools of water that accumulate in discarded car tires, flower pots, and filled drinking cups left outdoors.

“I believe all of the conditions where they’re present in Latin America and the Caribbean are also present in Texas and other Gulf Coast states,” said Hotez, who predicted the number of Aedes aegypti, which already reside in this part of the U.S., could start multiplying in March, when the weather warms up. “Which means we have time [to prepare]— and now’s the time to do it,” he said.

But controlling the main mosquito that carries Zika may prove more challenging in the U.S. than in Latin America, where governments are going into homes and spraying walls with pesticide, Hotez and Conlon said. Unlike other common mosquitoes in the U.S., they like to feed on humans during the day, which means people who live in homes without window screens would have a high infection risk, Hotez said.

“This is a day-biting mosquito, and that gets to be problematic because if you’re spraying when children are out playing … we’re going to have to make a better assessment of that,” Hotez said.

Conlon said standard mosquito control practices in the U.S. won’t work on the Aedes aegypti.

“Down in Central and South America, they’re using these thermal foggers— that can work and knock down the mosquito, but in the U.S, they’re not going to allow federal and state folks to allow them into their homes to do that,” Conlon said. “It’s not something that mosquito abatement will do, but public pressure may make them do that. People might demand something like that of their own volition.”

In preparation for the potential arrival of U.S.-borne Zika cases, Hotez called on Gulf Coast municipalities to provide people with protective window screens if they don’t have them.

Conlon echoed Hotez and said he expects mosquito control to lie primarily in the hands of municipalities. He called on local governments to begin spreading public awareness campaigns about the dangers of Zika and how to protect their homes and families against the Aedes aegypti.

In Texas— which has seen a case of sexual transmission and reported the first U.S. Zika case in mid-January— the department of health has prioritized such tracking and awareness campaigns, said Chris Van Deusen, spokesman for the Texas Department of State Health Services.

“That’s very much the discussion we’re having right now—making sure we know what the latest science is, and watching infections to see where they’re occurring, and if they’re traveling from Central and South America or the Caribbean if they have gotten sick with Zika,” Van Deusen told

“Public information—that’s our first line of defense,” said Van Deusen, who added the state is working with municipalities and the CDC to educate travelers about prevention methods.

Conlon also called on the federal government to provide funding to municipalities so they could test mosquitoes in labs, “so we can identify people who are bringing that disease into the country … and marshal our resources to rapidly wipe it out, once it occurs.”

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How the Zika virus outbreak may change US immigration policy

The Department of Homeland Security (DHS) already has guidelines in place for screening immigrants for communicable diseases before they enter the U.S. But screening for Zika may prove challenging because only one in five cases presents with symptoms, unlike Ebola, which could be suspected with the sign of a fever. Yet for some individuals and advocacy groups, the Zika outbreak feels all too familiar.

“That episode with Ebola should be a warning for the government, but I’m not seeing that,” Jessica Vaughan, director of policy studies at the Center for Immigration Studies, which advocates for reduced immigration to the U.S., told “I’m seeing the same things— ‘nothing to worry about here, this is not going to affect us, we don’t need to have any steps in place’— and that worries me.”

Vaughan said she predicted an increase in immigrants from Zika-afflicted countries but couldn’t quantify that prediction due to a lack of updated information. She also said she could only speculate as to whether policy in places like El Salvador and Colombia, which have advised women against pregnancy during the outbreak yet do not legally allow abortions, would impact immigration rates to the U.S.

“I am in no way a public health expert, but I find it remarkable that officials in these countries would be recommending against having children because of the threat of this, and I think that should be an alarm for U.S. authorities to take this seriously,” Vaughan said. “It’s hard to say what the immigration implications of that would be, but I do think that one thing we know for sure is there’s currently a very large flow of people from El Salvador [who are] coming illegally, and have been able to stay,” she added, referencing Obama’s open-door policy to El Salvadorian women and children who may seeking asylum after fleeing domestic or generalized violence.

“It’s very possible that women in El Salvador will see an opportunity to come here not only because they may see that they have more opportunity here,” she said, “but if they’re afraid that there may be some health problems with having children, they know they’re going to get better care here— or at least they can perceive it.”

Vaughan urged the federal government to consider requiring people traveling from Zika-afflicted areas to get certified before they are allowed to enter the U.S. on a tourist or temporary visa.

“That will affect a lot of people, but that’s what immigration controls are for,” she said. “We shouldn’t hesitate to use them. SARS was a problem in Asian countries, and they had no apologies or qualms at all about imposing travel restrictions. For some reason, we have difficulty saying, ‘No’ to people.”

Ali Noorani, executive director of the National Immigration Forum, an advocacy group for immigrants in the U.S., said restricting the U.S. economy from the rest of the world wouldn’t be worth it to try to suppress Zika.

“When you go back to SARS— when you go back to any of these epidemics— the primary mode of transmission is really business, travel tourism, and then you get immigration,” Noorani, who received a master’s of public health in epidemiology and environmental health from Boston University, told

Sandro Galea, dean of the school of public health at Boston University, wrote an editorial in the Boston Globe that argued against comparing Zika to Ebola. He told that he believes tightening immigration restrictions would be ineffective at preventing Zika’s spread to the U.S.

“Our approach to Zika should be of prudent caution to make sure people at high risk— which is women at early stages of pregnancy should avoid areas where Zika is currently endemic,” Galea told “But using Zika as an excuse to make arguments against immigrations or those people is really based on a deep misunderstanding of the science and biology of Zika, and I think betrays pre-held views of people that are looking for an excuse to make a particular point.”

He called for more investigation into whether Zika may be sexually transmissible but said, ultimately, Zika is an arbovirus, meaning it is transmitted primarily through insects, and in this case, mosquitoes.

“I think using Zika as an anti-immigrant push is ridiculous,” Galea said.

Noorani argued for more scientific study of Zika before health officials and the public jump to conclusions.

“Frankly, the science needs to catch up to the information, and it just seems that there is a  lot of information out there that is changing very quickly, but the science isn’t necessarily backing up the info yet,” Noorani said. “So what we want to make sure happens is, No. 1, that the science proves what the right screening measures are for the individuals who are in these countries, but most importantly that the public doesn’t panic.”