The World Health Organization declared the rise in birth defects linked to the Zika virus outbreak a public health emergency on Monday, underscoring the seriousness of the problem and paving the way for more money, greater attention and a coordinated global response.

Doctors connect Zika, which is spread by mosquitoes, to a surge in neurological disorders and the birth defect microcephaly, in which infants are born with abnormally small heads and incomplete brain development. WHO officials say clusters of these problems – not the Zika virus itself, which usually causes mild illness – led to the declaration of a "public health emergency of international concern."

Experts agree that Zika virus is "strongly suspected, though not yet scientifically proven" to be the cause of these problems, and "as a precautionary measure, a coordinated international response is needed," WHO Director-General Margaret Chan said.

This is the fourth time the WHO has declared a public health emergency. WHO declared two emergencies in 2014: the Ebola outbreak in West Africa and a resurgence of polio in Syria and other countries. The H1N1 swine flu pandemic prompted an emergency in 2009.

David Heymann, chairman of the WHO Emergency Committee, said his group's decision was a difficult one, particularly because Zika alone is not a clinically-serious illness in most people. But officials say an emergency declaration will help intensify mosquito control efforts and expedite the creation of a more rigorous diagnostic test and a preventive vaccine.

Zika first appeared in the Western Hemisphere in May, and the outbreak has now spread to 25 countries and territories.

The U.S. Centers for Disease Control and Prevention said no locally-transmitted cases have been reported in the continental United States. The illness has been reported in travelers returning from affected countries, including a student at the College of William and Mary in Virginia who contracted the virus while traveling in Central America over winter break. That student is expected to recover.

Locally-transmitted Zika has been reported in Puerto Rico,  the CDC said. It has warned pregnant women to avoid travel to areas with outbreaks.

Ashley Thomas Martino, an assistant professor of pharmaceutical sciences at St. John’s University in New York, said the WHO's action will free up resources for mosquito control and other actions to reduce transmission.

"They always want to err on the side of caution," said Martino, who teaches about infectious diseases. "You're talking about people's health and fetal development."

Leonard Krilov, chief of pediatric infectious disease at Winthrop University Hospital in Mineola, NY, said although severity can vary, children with microcephaly can potentially experience motor and learning delays, wind up wheelchair-bound and be "neurologically devastated."

Pregnant women and their babies are at the highest risk from the virus, which doesn't spread directly from person to person. Most people with Zika have no symptoms, but some develop a rash, joint pain, a low fever, pink eye and headaches.

 Anthony Fauci, director of the U.S. National Institute for Allergy and Infectious Diseases, has said doctors are working to develop a vaccine against Zika, using those already in development against West Nile virus, which is spread by the same type of mosquito. 

After weathering criticism for a slow response to the Ebola outbreak, WHO felt pressure to act decisively on Zika, said Thomas Russo, professor and chief of the division of infectious diseases at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo. "They're trying to get ahead of it," he said.

But Russo says it may take months for researchers to know for sure whether Zika causes microcephaly in infants or a rare neurological syndrome in a small number of healthy adults. For now, he said, average Americans don't need to worry that much about the virus. 

"If you're not pregnant," he said, "the concern you should have is minimal."

 

 

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