A team of U.S. government disease detectives launched an eagerly anticipated research project in Brazil on Monday designed to determine whether the Zika virus is really causing a surge of serious birth defects.
A 16-member team of epidemiologists from the Centers for Disease Control and Prevention began training dozens of Brazilian counterparts in Joao Pessoa, Brazil, in preparation to begin work on Tuesday. The researchers will gather data on hundreds of Brazilian women and their children.
"Having the data at this point in time are very critically important for understanding the impact Zika might be having in the future and as it spreads in the region," says J. Erin Staples, a CDC medical officer leading the CDC team in Brazil.
Scientists believe there has been a significant increase in microcephaly, a condition that causes babies to be born with abnormally small heads and brain, since Zika started spreading widely in Brazil. That strongly suggests that the virus is to blame. Zika has been found in the brains of a small number of babies with microcephaly, but that still does not prove the virus is to blame.
"Taking that and saying the 4,000 to 5,000 cases of microcephaly reported in Brazil are due to Zika is a very big jump," Staples says.
To try to better understand whether the association is real, the CDC is launching what is known as a "case-control" study, which involves comparing cases of people with diseases with similar people who did not have disease to try to identify the cause.
On Monday, the CDC formed eight teams of American and Brazilian investigators. On Tuesday, the teams fanned out in the region searching for about 100 mothers who gave birth to babies with microcephaly since the Zika outbreak began.
The teams will collect blood samples from the mothers and children to test for signs of Zika infection, examine the babies and gather detailed information from the mothers. Among the information the researchers plan to collect is whether the women experienced any symptoms of Zika infection during their pregnancies and, if so, when.
The investigators will also ask the women a series of questions aimed at identifying any other factors that may have played a role in the birth defects, such as whether the women had any other infections, including toxoplasmosis or cytomegalovirus. In addition, they'll try to determine whether the women were exposed to anything in the environment, such as mercury or pesticides, that could be to blame.
The investigators planned to do the same thing with several hundred other women who are similar in terms of their ages, locations and socioeconomic status who gave birth to healthy babies around the same time. The researchers will then compare the two groups.
The hope is that this study will either provide more definitive evidence establishing the link between Zika and microcephaly or identify other factors that may be to blame, either in combination with Zika or instead of Zika.
"What we're really trying to do is to better understand what's going on in terms of the size, the scope and the causes of microcephaly," Staples told NPR's Shots blog last week. "We want to better understand the role the Zika virus has in the outbreak of microcephaly."
Staples estimated it would take three or four weeks to collect all the data, but was unsure how long the analysis would take.
But "hopefully from all this work we will glean some information that will be able to help us prevent other children from being born microcephaly," Staples says.
The virus is spreading rapidly throughout Latin America and the Caribbean. Dozens of travelers have arrived in the United States after being infected elsewhere, but so far the virus is only known to have spread once in the continental United States, and that was through sexual contact.
The mosquito that spreads the virus is found in parts of the United States, but health authorities have said they are optimistic any transmission in this country would be quickly controlled.
STEVE INSKEEP, HOST:
Now let's track the work of disease detectives from the U.S. Centers for Disease Control and Prevention. They've arrived in Brazil to investigate the Zika outbreak that has set off a global health emergency. NPR's Rob Stein is with them. And, Rob, where are you exactly in Brazil?
ROB STEIN, BYLINE: Yes, good morning, Steve. I'm in a city called Joao Pessoa. It's in the northeast corner of Brazil, and this is a part of Brazil that's been hit really hard by Zika. It's really part of the epicenter of the outbreak. And as it happens, I just wanted to sort of mention, that this time of year this is the first place the sun rises anywhere on the continent. So in that way it's kind of an appropriate place for the CDC to be trying to shine a light on this baffling medical mystery.
INSKEEP: What is the question on their minds?
STEIN: So they're really trying to examine this crucial question, which is, is the Zika virus - you know, this virus that everybody thought was very much obscure and everybody thought was pretty harmless until recently - really causing this terrible birth defect, this microcephaly, which causes women to give birth to babies with abnormally small heads and severely damaged brains? And they've come here because so many pregnant women have gotten infected with the virus so that gives them really the best shot at getting to the bottom of what's going on.
INSKEEP: Although this is in a way disturbing, Rob Stein, because we have had so many new stories about the Zika virus causing these problems, what evidence is there to actually prove that it's true?
STEIN: Yeah, I know. I mean, health authorities have been saying at this point that the Zika virus is what they're saying guilty until proven innocent, and that's because the evidence has been mounting that there is a link between Zika and microcephaly. And the reason for that is, you know, in Brazil for example, it looks like there was this big spike in this - what had been a rare birth defect that began right after Zika arrived and started spreading like crazy, but that's really just circumstantial evidence. So they've been trying to strengthen the case and strengthen this link, and they have found other evidence. They've found the virus in the brains of a few babies with microcephaly who died shortly after birth. That makes the case stronger but it still doesn't prove it. And so the CDC's trying to make the case as airtight as possible.
INSKEEP: What puts it beyond a reasonable doubt - to use that term from law?
STEIN: Yeah so what the CDC's doing here is they sent 16 epidemiologists, and they're teaming up with their Brazilian counterparts to form eight teams to do what's known as a case control study. And this is really hardcore, shoe-leather disease detective work. They're literally going to fan out in the region and go door-to-door to try to track down at least a hundred women who have had babies with microcephaly since the Zika outbreak began. Once they find them they'll gather as much information about them as they can. They'll, you know, take blood samples from the mothers and from the babies to test for signs of the Zika infection. And they'll ask the mothers lots and lots of questions. Did the moms have symptoms of Zika when they were pregnant? If they did, when exactly in the pregnancy? And - this is the key thing - they're also going to try to find out if there's anything else that may explain what was going on that's not Zika. Did they have, you know, any other infections that are known to cause microcephaly or maybe infections that, combined with Zika, may be the cause? Or were they exposed to something in the environment, some sort of toxin that may be to blame? They'll do the same thing with hundreds of other very similar women who had healthy babies about the same time and compare them to see if they can make this link stronger or debunk it if it's not true.
INSKEEP: When you said shoe leather, you meant it. Rob, thanks very much.
STEIN: Oh, sure, nice to be here.
INSKEEP: That's NPR Health Correspondent Rob Stein in northeastern Brazil, where scientists are trying to prove beyond a doubt that the Zika virus is responsible for birth defects. Transcript provided by NPR, Copyright NPR.