A rash of birth defects in Brazil, likely linked to the mosquito-borne Zika virus, has the U.S. Centres for Disease Control and Prevention poised to issue a travel warning for pregnant women.
Last year in Brazil thousands of babies were born with microcephaly, a brain disorder experts associate with Zika exposure. Babies with the condition have abnormally small heads, resulting in developmental issues and in some cases death.
A travel warning is wise
A CDC travel advisory was expected Friday. But it wasn't known if it would include Latin American and Caribbean countries other than Brazil where mosquitoes can also transmit the virus.
"We now have an accumulating number of cases in babies from miscarriage or who were born with microcephaly with evidence of Zika," Dr Lyle Petersen, director of vector-borne diseases at the CDC's National Centre for Emerging and Zoonotic Infectious Diseases, told CNN.
Dr Marc Siegel, an associate professor of medicine at NYU Langone Medical Centre in New York City, thinks a travel warning is wise, but said people shouldn't assume they will get infected if they visit Brazil."
"It's extremely rare, but it's not impossible for a pregnant woman to get Zika on a trip to Brazil," he said.
At least 14 cases of Zika have appeared in the United States in people who travelled out of the country, according to news reports. The CDC is testing specimens from other returning travellers, so that number might increase.
The CDC does not, however, expect major outbreaks of Zika in the United States. Outbreaks of other mosquito-borne diseases in the United States "suggest that Zika outbreaks in the U.S. mainland may be likely limited in size", Petersen said, according to CNN.
Greatest risk during first trimester
Siegel, however, is more pessimistic. When people bring the virus into the country and are then bitten by a mosquito, then the mosquito is infected and can infect other people it bites, he said. "I think that's extremely likely," he added.
In late November, Brazil warned women not to get pregnant after a surge in microcephaly was linked to the virus.
More than 2,400 cases of microcephaly were seen in 20 Brazilian states in 2015, compared with only 147 in 2014, news agencies reported. Petersen told CNN the number has since risen to 3,700.
Meanwhile, the World Health Organisation (WHO) is reportedly conducting research to determine how Zika affects foetuses. Brazilian health officials think the greatest risk of microcephaly and malformations happens during the first trimester of pregnancy.
The Zika virus is spread by the Aedes mosquito – the same one that carries other diseases that infect humans, including yellow fever, West Nile, chikungunya and dengue.
The virus causes relatively mild symptoms fever, headache, skin rash, red eyes and muscle aches, according to the CDC. Symptoms usually clear within a few days. There is no vaccine or specific drug to treat this virus
Besides South America, Zika virus has been found in Puerto Rico, Africa and Southeast Asia.