World boosts study of Zika, as virus seen spreading

A public health technician inspects an Aedes aegyti mosquito in a research lab to help prevent the spread of Zika virus and other mosquito-borne diseases at the entomology department of the Ministry of Public Health, in Guatemala City.

U.S. health officials are stepping up efforts to study the link between Zika virus infections and birth defects in infants amid predictions for widespread circulation of the mosquito-borne virus within the United States during warmer months. The Director of the National Institutes of Health on Tuesday called for intensified efforts to study the impact of Zika infections, citing a recent study estimating the virus could reach regions where 60 percent of the U.S. population lives.

The mosquito-borne virus has been linked to brain damage in thousands of babies in Brazil. There is no vaccine or treatment for Zika, a close cousin of dengue and chikungunya, which causes mild fever and rash. An estimated 80 percent of people infected have no symptoms, making it difficult for pregnant women to know whether they have been infected. On Monday, the World Health Organization predicted the virus would spread to all countries across the Americas except for Canada and Chile.

In a blog post, NIH Director Dr. Francis Collins cited a Lancet study published Jan. 14 in which researchers predicted the Zika virus could be spread in areas along the East and West Coasts of the United States and much of the Midwest during warmer months, where about 200 million people live.

The study also showed that 22.7 million more people live in humid parts of the country where mosquitoes carrying the virus could live year round. Given the threat, Collins said "it is now critically important to confirm, through careful epidemiological and animal studies, whether or not a causal link exists between Zika virus infections in pregnant women and microcephaly in their newborn babies." Microcephaly results in babies being born with abnormally small heads.

There is still much to learn about Zika infections, experts said. For example, it is not clear how common Zika infections are in pregnant women, or when during a pregnancy a woman is most at risk of transmitting the virus to her foetus.