Dejailson Arruda holds his daughter Luiza, who was born with microcephaly after her mother was infected with the Zika virus following a mosquito bite, at their house in Santa Cruz do Capibaribe, Pernambuco state, Brazil.

In the early weeks of Angelica Pereira’s pregnancy, a mosquito bite began bothering her. At first it seemed a small thing. But the next day she awoke with a rash, a headache, a fever and a burning in her eyes. The symptoms disappeared within four days, but she fears the virus has left lasting consequences.

Pereira’s daughter Luiza was born in October with a head more than an inch (3 centimeters) below the range defined as healthy by doctors, a rare condition known as microcephaly that often results in mental retardation. A neurologist soon gave Pereira and her husband more bad news: The brain damage had caused cerebral palsy.

“My heart stopped. All I kept thinking about was all the struggles and discrimination my baby will suffer,” said Pereira, a 20-year-old seamstress who lives in Santa Cruz do Capibaribe, a small, garment-manufacturing city in northeast Brazil.

More than 2,700 babies have been born in Brazil with microcephaly this year, up from fewer than 150 in 2014. Brazil’s health officials say they’re convinced the jump is linked to a sudden outbreak of the Zika virus that infected Pereira, though international experts caution it’s far too early to be sure and note the condition can have many other causes.

Brazil alone estimates it’s already had between 440,000 and 1.3 million cases of Zika since the first local transmission of the virus was detected in May. The mosquito-borne disease was first identified in the Americas less than two years ago and has spread rapidly across South and Central America.

“We are looking at the beginning of an epidemic in a country that has in between 200,000 and 300,000 births per year, which shows how worried we are. It’s a virus we don’t know that much about,” said Rodrigo Stabeli, vice president of the Rio de Janeiro-based Fiocruz research institute. “We are preparing for the unknown.”

Brazilians are so concerned that some obstetricians, such as Helga Monaco at Sao Paulo’s Samaritano Hospital, recommend women avoid becoming pregnant during the rainy season when mosquitoes are most prevalent.

“All the women I see at the hospital or in my office who are pregnant or wanting to get pregnant are very alarmed,” she said.

The Zika virus, first detected in humans about 40 years ago in Uganda, has long seen as a less-painful cousin to dengue and chikunguya, which are spread by the same Aedes mosquito. Until a few months ago, investigators had no reported evidence it might be related to microcephaly.

Suspicion arose after officials recorded 17 cases of central nervous system malformations among fetuses and newborns after a Zika outbreak began last year in French Polynesia, according to the European Center for Disease Prevention and Control.

And in November, Brazilian researchers reported the Zika virus genome had been found in amniotic fluid samples from two women whose fetuses were been diagnosed with microcephaly by ultrasound exams. Brazil announced on Nov. 28 that researchers had found the Zika virus present in brain tissue of a newborn with microcephaly who died.

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