NEW HAVEN, CONNECTICUT — In the first half of 2015, Brazilian health officials prepared to take on the fast-spreading, mosquito-borne chikungunya virus, which had arrived from Africa in 2013.
And then came Zika.
Brazilian physicians first recognized it in May 2015. “We knew at once that Zika posed serious problems,” said Paulo Gadelha at a Yale School of Public Health presentation last Thursday by 3 physicians from the Oswaldo Cruz Foundation, Brazil's leading public health research institute.
A year and a half after the virus was identified in Brazil, the country is the epicenter of a Zika epidemic. Women with confirmed Zika infections have given birth to more than 2,000 babies with major central nervous system malformations, according to the October 13 case report from WHO. Most of the babies have abnormally small heads, or microcephaly (defined as a head circumference more than two standard deviations below the mean for gestational age and sex).
“When we had the first case in May of last year, physicians were impressed that they were seeing an infestation of microcephaly very different from what they had seen before,” said Gadelha, president of the foundation.
3 months after Brazilian public health officials declared a national public health emergency in November 2015, WHO called Zika an international emergency. Since then, Zika infections have been reported in the United States and in most of Latin America and the Caribbean.
Researchers now believe that even when Zika-exposed children appear normal at birth, they may develop neurological problems such as convulsions and vision problems, said Gadelha’s colleague, Luiz Galvão.
Zika is an elusive target: it is the first mosquito-borne virus that also spreads through sexual contact. It has been found in semen, urine and saliva, and it can cross the placental barrier. This raises new questions: How long after infection will a man carry the virus in his semen? Will a woman infected with Zika before pregnancy pass it on to her fetus?
Gadelha noted that although Zika infection is common in Brazil’s west-central region, few babies there have been born with microcephaly. Unlike in northeastern Brazil, most people in the region have been vaccinated against yellow fever. “Perhaps the vaccine becomes another factor that will enhance immune response,” said Gadelha. “A lot of research will be needed.”
Research so far includes a large multinational study launched in June—a collaboration between the Oswaldo Cruz Foundation and the U.S. National Institutes of Health. The Zika in Infants and Pregnancy study aims to learn more about the effects of the virus by following 10,000 pregnant women beginning in the first trimester, and then monitoring the health of their babies. Study participants include women from Puerto Rico, Guatemala, Nicaragua, Colombia and Brazil.
Gadelha believes that the alarm generated by Zika could speed the development of new ways to confront not only Zika, but also other viruses carried by Aedes aegypti mosquitoes. In one promising experiment, researchers have introduced Wolbachia bacteria into mosquitoes that carry Zika, dengue, chikungunya and yellow fever. This common bacterium blocks maturation of the viruses, and when mosquitoes breed, they pass on Wolbachia to their offspring.
“We have a fascination for technology,” said Oswaldo Cruz researcher Paulo Buss, but “the social dimension is very important.” Zika is most prevalent in poor neighborhoods, he said, and structural changes can stem disease. These include regular garbage removal; screens on windows; better nutrition; accessible health care; and piped water, which eliminates the need for household water tanks where mosquitoes breed.
Integrated virus management that combines several approaches has proven to be both cheaper and more effective than just spraying. “We are completely against this idea of widespread use of pesticides,” said Gadelha, who commented that manufacturers of insecticides push for their use. “Mosquitoes adapt and become resistant.”
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