Developing an effective one may take years, however, while concern about the virus going global is growing.
A health ministry employee fumigates a home against mosquitos that may carry the Zika virus in El Salvador on Thursday.
By Steve SternbergJan. 22, 2016, at 1:45 p.m.+ More
Alarmed at the surge of Zika virus in the Americas, the U.S. government has launched an effort to develop a vaccine.
"We're already starting on it," says Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. But while workers at the institute's Vaccine Research Center are armed with lessons learned from working to counter West Nile virus, chikungunya virus and dengue fever, Fauci says developing a vaccine for Zika will require "an extensive research and development effort."
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The Pan American Health Organization now says the virus has spread to more than 20 countries and territories, and Brazil has reported that more than 3,800 babies have been born with microcephaly – a condition believed associated with the virus that involves a small cranium and brain and can lead to lifelong cognitive impairment.
"No matter how you slice it, with a twentyfold increase in microcephaly – to 3,800 cases at last count – that's a serious issue," Fauci says. "We've got to do something about it."
In addition, the virus appears to be linked to a rise in a nerve ailment called Guillain-Barre syndrome that causes paralysis in adults. "El Salvador usually reports an average of 14 cases a month," says Dr. Marcos Espinal, the Pan American Health Organization's director of communicable disease programs. "Between December and January, they reported 46 cases."
So far, public health efforts to curb the mosquito-borne Zika virus have focused on avoidance, with Brazil and El Salvador urging women to hold off on getting pregnant. For its part, the U.S. Centers for Disease Control and Prevention is urging pregnant women to avoid traveling to a lengthening list of affected areas – updated Friday to 22 destinations – and all travelers to follow strict precautions to avoid mosquito bites.
With a handful of Zika infections reported in travelers returning to the United States and with others undergoing testing, some U.S. public health officials are concerned that the virus may gain a toehold in the country. The most likely locations are along the Gulf Coast and in Florida, though Fauci and others say an extensive spread is unlikely.
"We're unlikely to have serious local spread," Fauci says. "This is very similar to dengue, where it laps at our shores, people get infected in other regions and come back to the United States. Will local cases turn into major outbreaks? I don't think so. There have been millions of cases of dengue in South America and the Caribbean for years and years."
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That doesn't mean, Fauci says, that the U.S. shouldn't be concerned, because two mosquitoes that carry Zika – Aedes aegypti and Aedes albopictus mosquitoes – are found in the Southeast, and local outbreaks may occur. "I think we're very likely to see a large number of imported cases as a lot of people go to South American and the Caribbean and come home," he says.
The consequences of becoming infected are so dire, researchers say, that developing a vaccine must be an urgent priority. "Everywhere and anywhere there's vulnerability, there's pressure for a vaccine," Fauci says.
The virus spreading globally is a real possibility, says Waleed Al-Salem, a researcher at the Liverpool School of Tropical Medicine and an adviser on insect-borne diseases to the Saudi Arabia Ministry of Health. Aedes aegypti mosquitoes, he says, are widely distributed in Southeast Asia, southern India, Pakistan, most African countries, the Arabian Peninsula, southern Europe and most Latin American countries.
Either the mosquito or an infected traveler can carry the virus to another country, and opportunities for global transmission abound. Next month, Carnival celebrations begin in Brazil, which typically are a major draw for globe-trotting travelers. This summer, Brazil is to host the Olympics. In eight months, millions of Muslim travelers from around the world – including from Latin America – will converge in Mecca, Saudi Arabia, for the annual hajj pilgrimage.
"Every year, 2 to 3 million people travel to Mecca," Al-Salem says. "Some of them may have Zika."
He notes the Saudi Ministry of Health takes precautions to prevent obviously ailing hajj pilgrims from infecting others and steps up mosquito-control efforts.
"Mosquito control is extremely important. If you don't get bitten, you don't get Zika," says Dr. Stanley Plotkin, professor emeritus at the University of Pennsylvania and developer of the rubella vaccine.
The rapidity of Zika's spread, Plotkin says, suggests there's a significant amount of virus in an infected person's blood. "That means a mosquito biting someone is very likely to become infected and transmit the virus to others," he says.
Yet mosquito control is only part of the solution, given how widely the insects breed and how difficult it is to wipe them out. A vaccine offers a more permanent solution, Plotkin says, but developing one will likely take years. Many scientific questions must be answered first.
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Perhaps the biggest is whether people who have been infected with Zika virus are immune to re-infection from another mosquito bite after they recover. "If they are, a vaccine is likely to work," Plotkin says. "If they're not, we're in trouble."
Another key question is what sort of vaccine to create. It's risky to give pregnant women a vaccine made of live, weakened virus because they are more vulnerable to infection, which also places their fetus at risk, Fauci says. One approach he envisions is a laboratory construct made of DNA with a Zika virus "insert."
Big pharmaceutical companies so far have announced no plans to develop a vaccine. Merck – maker of a measles, mumps and rubella vaccine, among others – did not respond to a request for comment. And so far, pharmaceutical giant Pfizer is "not in the hunt for Zika," spokesman Dean Mastrojohn says.
The National Institute of Allergy and Infectious Diseases also plans to boost funding to Brazilian grantees to jump-start research efforts. "That's the fastest way to get them to work on diagnostics and vaccines," Fauci says. "We need better diagnostics so that women who are pregnant will know, and not have to guess, whether they're infected."
