HAITI is reporting its first cases of a mosquito-borne virus that is rapidly spreading in the Americas and now appearing in the Caribbean is suspected of causing over 3,500 birth defects in Brazil.

Public Health Minister Florence Duperval Guillaume announced on Friday that there have been five confirmed cases of the Zika virus in Haiti. She says they are all in the area of Port-au-Prince, the country’s overcrowded capital.

Zika is a Dengue-like virus that causes a mild illness in most people. The US Centers for Disease Control and Prevention (CDC) said this week that evidence of the virus was found in Brazil in the placentas from two women who miscarried and the brains of two newborns who died. Those who were born had small heads, a rare condition known as microcephaly. Brazil has been experiencing the largest known Zika outbreak and a surge of birth defects. Many Haitians live in shacks with little protection from mosquitoes.

“The evidence is becoming very, very strong of the link between the two,” said Dr Lyle Petersen, director of mosquito-borne diseases at the CDC. Finding the virus present in brain tissue is “very significant”, he said.

Dr Petersen warned that the link is not yet definite and said that a team of CDC investigators is travelling to Brazil in a few weeks to conduct more studies and learn what risks face pregnant women. “It’s possible that there may be some other co-factors involved,” he said.

Zika is spread by the same Aedes mosquito that can carry Dengue and Chikungunya. There are no known cases of people contracting the virus in the US mainland, though it has been seen in returning travelers. Puerto Rico reported its first case of Zika two weeks ago, and 13 countries in Latin America have also seen infections.

“I don’t think anybody has any idea how Zika is crossing the placenta into these fetuses, or why Zika is doing it and other closely related viruses like Dengue don’t,” said Scott Weaver, director of the Institute for Human Infections and Immunity at the University of Texas Medical Branch in Galveston.

Dr Ernesto Marques, an infectious diseases researcher at the University of Pittsburgh who is also studying Zika and the birth defects outbreak in Brazil, said he is finding so far that a very small percentage of pregnant women who reported Zika symptoms gave birth to babies with microcephaly. He said a problem facing epidemiologists is the lack of laboratories that are able to test for Zika. Dr Marques said estimates that the country had between 440,000 and 1.3 million cases of the virus in 2015 are not reliable.

“It needs to be better diagnosed. We don’t know many, and we need a better response,” he said.

Brazilian health authorities have said there’s no question Zika is behind the birth defects. The Health Ministry said on Tuesday that 3,530 babies have been born with microcephaly in the country since October. The number was less than 150 in 2014.

Now the government finds itself with a growing number of children with mental retardation concentrated in one of the poorest regions of the country in the northeast. On Wednesday, Alberto Beltrame, national secretary of health care, said the government would invest $163 million to provide care and physical and speech therapy to those babies through the first three years.

Associated Press