The mosquito-borne virus, Zika, that has been linked to severe brain damage in infants may be causing another serious health crisis as well, Brazilian officials and doctors warn: hundreds of cases of a rare syndrome in which patients can be nearly completely paralysed for weeks. That number has jumped to over 3,700 cases since the virus was first detected in Brazil.

Eighteen countries and regions in the Americas have confirmed cases, such as Barbados, Ecuador, French Guiana, Guatemala, Guyana and Haiti.

Meanwhile, US health authorities have expanded a travel warning for pregnant women to avoid 22 places in Latin America and the Caribbean due to the Zika virus.

Around 4,000 babies in Brazil have been born with abnormally small heads since October 2015 - compared to just 150 infants in the whole of 2014.

They said 26 of the mothers reported having had a rash during pregnancy.

Does it really cause birth defects?

It also reported that the person infected is a 42-year-old woman with no history of previous travel during the incubation period of the virus.

'This is a significant advance, but we still can not scientifically state that Zika is the cause of microcephaly, ' said Jean Peron, an immunology expert who is experimenting on pregnant mice at the University of Sao Paulo's Institute of Biomedical Sciences.

But there are some strong hints.

That's not clear, either.

Ruiz said there have been 12 cases of people with Guillain-Barre who had earlier had symptoms similar to those of Zika.

"There is much that we do not yet know about the Zika virus and its effects during pregnancy, for example whether pregnant women are of greater risk of infection than non-pregnant individuals", ACOG President Dr. Mark DeFrancesco said in the statement reported by Medical Xpress.

Is there an especially unsafe time in pregnancy? So far no cases of newborns suffering from microcephaly have been recorded.

Marcos Espinal, the head of the Pan American Health Organization's communicable diseases department, delivered the bad news that "travel restrictions will not stop the spread of Zika" and he expected that it would spread throughout Latin America. It is uncommon for people infected with Zika to need hospital treatment.

A 42-year-old woman from St. Croix has tested positive for the Zika virus, according to an Associated Press report.

Answers could take months. Many people do not show any signs of infection.

Aedes albopictus mosquitoes, which are found throughout the USA and are known for transmitting dengue fever and chikungunya, may also transmit the virus, the CDC said Friday. The symptoms typically begin 2 to 7 days after a person is bitten by an infected mosquito.