How much harm can the Zika virus do?
That's the question that is bedeviling researchers in Brazil. It's not just the matter of a possible link to brain damage in babies born to mothers who contracted the virus during pregnancy. There have also been suspected cases of adult patients who suffered temporary hearing loss.
Researchers are trying to make sense of it all, and yet they lack very basic information. Even the number of cases and the degree to which it has spread are unknown.
That makes it hard to figure out the true impact of Zika. One reason that it's hard to know whether there's a link between Zika and reports of brain damage is that it's hard to know whether a pregnant woman actually had the virus.
Doctors in Brazil say the most important thing they need to have as quickly as possible is a reliable and fast way to test for the virus.
"The big difficulty right now is really to be able to test with certainty if someone had Zika or some other infection, like dengue, which is very similar," says Dr. Rafael Franza, an immunologist in the city of Recife, the epicenter of the outbreak.
Franza heads a team working with Glasgow University to develop a rapid test. At the moment, he says, the only way to determine whether you have been infected is to do a blood test within five days of the infection. The first problem: Most cases are asymptomatic, so you may not know you have Zika at all. The second problem: resources.
He says only 16 public labs in Brazil are equipped to test for the virus, which requires a molecular study of the sample. Brazil's Ministry of Health has announced it is sending out equipment so that a total of 27 labs will be able to do the blood tests.
Brazil is also making it mandatory starting next week for hospitals to report how many suspected cases of Zika they are dealing with.
This lack of testing ability affects the ability of doctors to determine how often cases of brain damage in infants are linked to Zika, says Dr. Manoel Barral. He is the director in Bahia of the Oswaldo Cruz Foundation, a Brazilian medical research behemoth.
In Bahia, doctors are also focusing on what happens to adults who caught Zika.
"The initial manifestations are kind of mild, like [a] rash, but if it's severe enough to cause microcephaly and brain damage, what else can be attributed to [the virus]? We have to investigate more," he says.
Indeed, there are indications that Zika in adults can have lingering neurological effects.
"The problem may be worse than we think," says Barral.
"After Zika they started with some symptoms like vertigo or dizziness and hearing loss and tinnitus [ringing in the ears]," says Dr. Viviane Boaventura, an ear, nose and throat specialist who works with Barral. She is studying 10 patients who are suspected of having had Zika.
Up to two months after contracting the virus, Boaventura reports, the 10 patients suffered measurable and significant hearing loss as well as lightheadedness. She has been monitoring these patients since May.
The symptoms require further investigation, she says, emphasizing that these effects seem temporary and almost all of the 10 patients have recovered fully.
"We are just starting," she says. "And we don't have a lot of patients to tell you if [the damage] will be reversible or it will be permanent."
Other questions are looming. If you've had the virus once, does that make you immune? Doctors assume so but don't know for sure. Can it be sexually transmitted? There are several cases that indicate it's possible.
With doctors now focusing on the virus, the hope is there will be answers in the weeks and months to come.