Brazilians Spraying and Praying for Dengue Vaccine Breakthrough
A cup of cloves, a half-liter of alcohol and a dollop of body oil: You won't find this homemade mosquito repellent in Brazilian drugstores, but the recipe went viral after a worried sanitarian posted a cell phone video on Facebook last week.
Amid one of their worst outbreaks of dengue fever -- 460,000 people infected and 132 dead this year -- Brazilians are understandably jumpy. That humming sound is aedes aegypti, a familiar pest storied for spreading yellow fever throughout tropical America and now enjoying a comeback as the vector for what has become a 21st-century pandemic.
Once a mostly Asian affliction, the dengue virus has gone global because of breakneck urbanization, bad management of water, haphazard public health care and travel on jets that can take passengers anywhere overnight. A 2013 study in Nature reckoned that dengue had infected 390 million people that year, with 94 million falling ill.
The outbreak is especially severe in the Americas, which have seen a 30-fold increase in the disease over the past 50 years. Counting hospitalization and sick leave, the disease costs the region at least $2.1 billion a year, says the Pan American Health Organization.
Brazil, alone, accounts for six of every 10 reported cases of illness from dengue worldwide.
There is no vaccine or cure for dengue, leaving Latin Americans reaching for the bug juice and praying for a scientific breakthrough. "The only weapon we've had till now is mosquito control," said immunologist Jorge Kalil Filho, who directs Instituto Butantan, a research center in Sao Paulo.
And yet follow-through on the protocol for combating insects is lax, partly because it was once such a success: Armies of bug killers all but eliminated the offending mosquito last century, then holstered their spray guns when yellow fever subsided in the 1960s. Urbanites didn't help by routinely ignoring official calls to do their part even as mosquitoes multiplied in their potted plants and rubbish.
And although dengue is a global scourge, it has drawn far less research funding than diseases such as HIV and Ebola. "We're hung up on mortality," Duane Gubler, a leading dengue expert with Duke-NUS Graduate Medical School, in Singapore, told me. "Because dengue has relatively low fatality rates, it gets far less attention."
Adding to the woes is global warming, which experts fear could expand the frontiers of the heat-seeking mosquito. Last year, Japan reported its first dengue outbreak in 70 years, and France is on the alert.
The good news is that prevention is making progress. Researchers at the University of Sao Carlos are tinkering with chemical deterrents, such as turmeric extract, which leaves mosquito larvae vulnerable to sunlight. Another Brazilian team is ginning up an ultrasensitive device to detect and trap mosquitoes by monitoring the frequency of their beating wings. Still others are weaponizing mosquitoes, introducing genetic modifications or bacteria into the bugs so that they will produce sterile offspring when they mate.
The most promising -- and vexing -- challenge is developing a vaccine. With four different serotypes, all of them present in the Americas, the virus is a moving target. Coming down with one strain of dengue is no protection against another.
The race is on in Brazil, where tests on three different vaccines are under way. Leading the pack is Sanofi Pasteur, the biotech firm, which after advanced field trials has claimed a 60 percent prevention rate for all strains of the disease and an 80 percent reduction in the hospitalization risk.
Close on their heels is the Instituto Butantan, working with the U.S. National Institutes of Health, which has asked health authorities for permission to launch its third phase of vaccine testing for 17,000 people throughout Brazil.
Earlier trials showed its vaccine was able to trigger antibodies -- "a cellular defense system," said Kalil -- effective against all four strains of dengue, with minimal side effects.
Kalil argued that jumpstarting the final testing phase could clear the way to deliver a vaccine to the public by 2016, much the way the U.S. Food and Drug Administration fast-tracked trial vaccines to deploy during the Ebola outbreak.
Giovanini Coelho, who heads Brazil's national dengue control program, is more cautious. "Many vaccines are a coin toss," he told me. "But we've had 5 million infections in the last five years, so even if we don't have the world's best vaccine, it would still be a blessing."
After years of neglect and mission drift in the public health establishment, Gubler is encouraged. "For the first time in 45 years in the field, I feel fairly optimistic. We have the tools to fight dengue, now we need to assure the funding."
Until the scientists can deliver, Brazilians can brace for their next dengue summer -- and more viral videos on Facebook.
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