An increase in deformities of newborns in Brazil is caused by infection from Zika virus that mothers contract during the first few months of pregnancy, the Brazilian Health Ministry announced Saturday.

The announcement comes on the heels of an epidemiological alert issued by the Pan American Health Organization warning residents about the unusually high number of microcephaly cases being reported in the region. Microcephaly causes babies to have abnormally small heads because of stunted brain development.  

The link between Zika virus infection and microcephaly was established through a test carried out by the Evandro Chagas Institute. Researchers detected the virus in the blood and tissue samples of a baby from Ceara who was born with microcephaly and eventually died. 

"This is an unprecedented situation in world scientific research," the ministry of health said. "The research on the subject should continue to clarify issues such as the transmission of the agent, its role in the human body, the infection of the fetus and period of increased vulnerability for pregnant women."

Initial analysis showed that the risk of babies being born with microcephaly because of the virus is particularly high within the first three months of pregnancy.

There are two other fatalities from Zika virus infection: a man from San Luis, Maranhao and a 16-year-old girl who were both thought to have contracted dengue.

Zika virus is transmitted by the same mosquitoes that transmit dengue and chikungunya viruses. The infection has been spreading rapidly in South America and the Caribbean. In Brazil, the virus was first detected in April, but it has now spread to 18 states with a total of 739 confirmed cases, BBC reported.

The Brazilian health ministry said 199 municipalities are at risk of being hit with Zika, dengue and chikungunya outbreaks, and it began a "national mobilization effort to contain the mosquito, Aedes aegypti, responsible for the spread of dengue, chikungunya and Zika."