Brazilian researchers baffled by Zika

Ahead of the World Health Organization (WHO) meeting in Geneva on 1 February, Dr. Rodrigo Stabeli, vice president of the Oswaldo Cruz Foundation (Fiocruz), Brazil's foremost public health research organization, told DW the rapid spread of the disease across the Americas justified his call.

"As Margaret Chan (WHO president) said, we are seeing an 'explosive' rise in cases," he said. "Looking at the transmission rates of this virus, I think Margaret should call a public health emergency."

Such a move would help to free up funding from member states and private donors to help in the fight against the disease. At present, though the virus has been registered in 22 countries in the Americas, Brazil is bearing the brunt.

The country's Health Ministry estimates that up to 1.5 million of its citizens may have been infected; 4,180 suspected cases of microcephaly, the infant brain damage which health authorities are linking to the Zika virus, have also been registered.

Lack of knowledge

But of all the worries current among Brazil's scientific community in the wake of the outbreak, perhaps the greatest is ignorance.

Of those 4,180 suspected cases of microcephaly, only 270 have been confirmed, and only six of those have a proven link to the Zika virus.

"The problem is that we know so little about the disease," said Dr. Denise Valle, an epidemiologist at the Oswaldo Cruz Institute, a major public health research center. "We need to understand this virus much better; at the moment it is still a mystery."

First identified in a rhesus monkey in Uganda's Zika forest in 1947, the virus only really began to cause concern in 2007 following the first notable outbreak among humans on Yap Island in Micronesia.

It was first recorded in Brazil in May 2015, and it was in November last year that the country's health authorities alerted the Pan-American Health Organization (PAHO) about a possible link between Zika and microcephaly.

'Compelling correlation' with microcephaly

So far most of the evidence for the link is based on a strong correlation between the virus outbreak and the incidence of microcephaly. But Brazilian researchers admit that correlation is not the same as causation.

"The evidence is very compelling," said Stabeli. "But we cannot say that it is a scientific certainty."

Stabeli also pointed out that the virus has been found in the amniotic fluid of two women whose fetuses had microcephaly. Brazil's Carlos Chargas Institute demonstrated recently how the virus could travel across the placenta.

Based on the current rate of increase in microcephaly over the past year, Fiocruz expects Brazil will have 16,000 cases by the end of 2016. Stabeli describes the situation as the country's worst health crisis since the Spanish Flu epidemic in 1918.

Complicating the situation yet further is the absence of effective testing for the virus. At present, the only available tests are molecular ones of a high degree of complexity. The tests can only be carried out in a highly specialized laboratory and they are only effective when the patient is expressing clinical symptoms, which is just during a three to seven day window.

"We are currently developing a serological test (from a blood serum) which would be able to tell whether the person actually had the virus (at an earlier date)," said Stabeli. "At the moment this kind of test is not on the market."

Practical preventive measures

In the absence of a cure or a vaccine, which will take at least three years to develop, prevention efforts have focused on eliminating the disease vector: the Aedes aegypti mosquito.

Over 220,000 soldiers are being deployed across the country to help health workers go door to door in affected areas to clear residences of potential breeding sites and to educate the public about the importance of removing pools of standing water.

Health officials estimate that around 80 percent of mosquito breeding sites are located on people's properties. Despite the scale of the challenge, Valle believes that the elimination campaign has a good chance of success.

"In Singapore in 2004 and 2005, they managed to stop an epidemic by mobilizing the population to eliminate breeding sites," she said. "In Rio de Janeiro in 2012 and 2013, we managed to reduce the mosquito population dramatically with the same approach."

For Valle, control of the epidemic is much more a question of permanently improving public sanitation than attempting to eliminate the mosquito.

"The enemy is not the Aedes aegypti," she said. "The enemy is ourselves."