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Recife, Brazil, is the epicenter of an outbreak of the Zika virus, which has its origins in Africa and is spreading globally — fast.

Science correspondent Miles O’Brien traveled to Brazil this week, where he reports on the Aedes aegypti mosquito that carries the virus and the doctors and government health workers who are treating and tracking infant microcephaly, the neurological condition that might be linked to it. Microcephaly is a condition where a baby’s head is abnormally small. It often comes with permanent mental and physical problems.

At one hospital in the city, pediatric doctors would normally see about 10 cases of the condition a year. Since August, that number has jumped to 10 to 20 a month, he reports.

Health workers are searching for the smoking gun link between the virus and infant microcephaly, while troops attack mosquito breeding grounds and mothers of affected children face the long-term consequences, Miles reports. He also brings us to the labs where immunologists hope the Zika virus samples held in deep freeze will lay the groundwork for better diagnostic tests, therapies and maybe one day a vaccine.

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JUDY WOODRUFF: Now to the growing effort to rein in the mosquito-borne Zika virus spreading through parts of South and Central America. It is suspected of being the cause devastating birth defects in children who are born to women who become infected during pregnancy.

Our science correspondent, Miles O’Brien, has been reporting on developments from Brazil, which has been hard-hit by the virus.

Tonight, he looks at ways doctors and scientists are racing to get ahead of the outbreak.

MILES O’BRIEN: It’s Carnival week in Brazil, the raucous run-up to Lent, when people take to the streets to party their worries away. But this year, it’s harder to mask reality, as a frightening epidemic also marches through the nation.

DR. ADRIANA SCAVUZZI, Obstetrician, IMIP: They come to us asking many questions, and we cannot say almost nothing with 100 percent sure. What we have to do is to support them. That’s all we have to do.

MILES O’BRIEN: Dr. Adriana Scavuzzi is an obstetrician at one of the largest hospitals in Recife, the epicenter of a fast-moving outbreak of the Zika virus, a flavivirus virus in the same family as yellow fever, West Nile and dengue.

In each case, the virus hitchhikes on a tenacious day-biting mosquito called Aedes aegypti that has origins in Africa and is now spreading throughout the globe. Two-month-old Nicollas Pereira has an abnormally small head, microcephaly.

Doctors at this hospital would normally see 10 cases like this a year. But starting in August, there were suddenly 10 to 20 a month.

Dr. Ana Van Der Linden is a pediatric neurologist. She says Nicollas must contend with an array of permanent mental and physical problems.

DR. ANA VAN DER LINDEN, Pediatric Neurologist, IMIP (through interpreter): With this impairment, we see that reflex reactions are good, but voluntary actions that depend on better brain development will be impaired. He will have bad motor skills and mental development. He can also have abnormal vision, hearing disorders and bone malformation.

MILES O’BRIEN: His mother, Elizangela, says she developed a rash while she was pregnant. As it turns out, she had the Zika virus, apparently after a mosquito bite.

ELIZANGELA PEREIRA (through interpreter): Sometimes, I worry. Sometimes, I wonder if he will survive, but I always believe that God will help. My only fear is losing him. But I’m at peace.

MILES O’BRIEN: Elizangela’s personal tragedy is part of an unprecedented global mystery.

DR. LAURA RODRIGUES, London School of Hygiene & Tropical Medicine: I think this is one of the most unexpected epidemiological situations, maybe in decades.

MILES O’BRIEN: Laura Rodrigues is an epidemiologist with the London School of Hygiene and Tropical Medicine who raced to her home country to help answer some questions in a hurry.

Even the numbers are a challenge. Brazilian government health workers are investigating more than four thousand suspected microcephaly cases that might be linked to Zika.

DR. LAURA RODRIGUES: There is so much we don’t know, and one of the things we don’t know is exactly how many babies are affected. Right now, there are pregnant women being exposed and possibly infected. It’s very difficult to predict.

MILES O’BRIEN: Zika’s enigmatic history offers us few clues. It was first isolated in Uganda in 1947. It circulated in Africa and a broad stretch of Asia, then popped up in the Pacific in 2007. The biggest outbreak, in 2013, was in French Polynesia, an estimated 19,000 cases.

But over the years, no one paid a lot of attention to Zika because the symptoms are generally mild. In fact, four out of five never know they have it. No one is sure why it took such a vicious turn.

DR. LAURA RODRIGUES: It could be biogenetic mutation of the virus, and it could be that just once they escaped Africa and got into urban, very densely populated areas, it was easier to transmit, or it could be something else, the mosquito maybe. It’s all happening very, very fast.

MILES O’BRIEN: Making a smoking gun connection between Zika in mothers and microcephaly in their unborn children is a challenge for scientists.

By the time infants are diagnosed, the virus is usually long gone. But here in Recife, the case grew stronger last week. At this government lab, researchers used a new test and found Zika antibodies in the spinal fluid of 12 babies with microcephaly, meaning the virus can reach the baby’s nervous system and brain in utero. Researchers believe the virus targets nerve cells as a fetus develops.

RAFAEL FRANCA, Immunologist: So this is where we keep the virus.

MILES O’BRIEN: Rafael Franca is an immunologist here. He showed me the deep freeze where they keep the Zika samples for research that will lay the groundwork for a better diagnostic test, therapies and maybe one day a vaccine.

RAFAEL FRANCA: I cannot say that we have the situation under control. I believe now the only way to control virus’ spreading is to eliminate the vector.

MILES O’BRIEN: That vector is the mosquito. In nearly every case, Zika is transmitted by a mosquito bite. The Brazilian government has deployed nearly 250,000 troops to wage war with the insects.

They have been spraying insecticides and adding larvicides to standing water where mosquitoes lay their eggs.

Gaspar Canuto is a Recife government health worker.

How much of this is to show the public you are doing something?

GASPAR CANUTO, Recife Public Health Worker (through interpreter): One hundred percent of this action is aiming to reduce the incidence of mosquitoes and also of the disease.

MILES O’BRIEN: Efforts like this, while well-intentioned, seem unlikely to stop the outbreak anytime soon in Brazil or in other countries hit by Zika, especially in Latin America.

The scale of this is pretty mind-boggling. A single female mosquito in her short lifetime will lay hundreds of eggs. And she’s looking for a place like this, standing water, not much more than a puddle. But what is really interesting is, that’s about al the water she needs.

With all this in mind, the Brazilian government is warning citizens that standing water can be dangerous. But in this slum in Recife, there is no running water.

DR. ADRIANA SCAVUZZI: Can you imagine a family that they don’t have even tap water? They have to keep water in the containers. So it makes the perfect environment for the mosquito. To try to solve the medical problem won’t be enough. You have to change the quality of people’s life. Otherwise, you will not solve this problem.

MILES O’BRIEN: Doctors here say the biggest frustration is they can’t fix what ails these babies, all because of a single mosquito bite. It has dramatically changed Elizangela’s life. She had to quit her job as a farmworker to care for little Nicollas.

ELIZANGELA PEREIRA (through interpreter): I think I will be here at the hospital forever. I do not know if he will be able to walk. I don’t know, but I believe that God will help me.

MILES O’BRIEN: One woman’s sad, but hopeful prayer this Carnival season. It’s still a time to try and forget your troubles, but in Brazil this year, a steady drumbeat of worry seems impossible to ignore.

Miles O’Brien, the PBS NewsHour, Recife, Brazil.

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