It all started one day in June 2007, with a sudden fever and intense vomiting. David Hancock says he should have gone to hospital straight away, but he thought it was a small infection. Still, I had the feeling that something was wrong, it didn’t feel like the flu.
And something really bad was about to happen. It took ten days for the 49-year-old to be diagnosed. During this time, he fell into a coma, his heart stopped several times, his lungs filled with fluid, and his brain became inflamed.
“I was in another world, you could say,” says David.
Eventually, doctors were able to make a definitive diagnosis: David had been infected with West Nile virus. All this because of a simple mosquito bite, right in front of his house in Glendale, a city near Phoenix, in the United States.
Northern hemisphere mosquito, southern hemisphere virus
Unlike malaria, dengue, yellow fever and Zika, West Nile virus is not transmitted by an invasive mosquito species such as Aedes aegyptibut mainly by the genus Culex (stilts), native to the northern hemisphere.
West Nile virus, however, is tropical in origin. It was first described in 1937 in the West Nile region of northern Uganda, and is named for the location where it was found.
It multiplies particularly well in birds. Thanks to them, it managed to leave Africa – migratory birds carried the virus to Europe and the United States. In 1999, it was registered for the first time in the United States. Today, it is the leading cause of mosquito-borne diseases in the country.
This is because the tropical virus found the Culex pipiensthe common mosquito. Native to Europe and North America, it is a particularly effective vector of the West Nile virus: when it bites an infected bird, it absorbs the virus and transmits it to another victim – which can be another bird, a horse or a person, as was the case with David.
Although the infection usually goes unnoticed and has no symptoms, about 1,300 people in the United States develop severe forms of the disease each year and 130 die from it.
Irony: David’s brother is a mosquito researcher
On June 18, 2007, David didn’t just have a fever and vomiting. He couldn’t swallow either. His wife, Teri, took him straight to the hospital. A mistake.
“We should have called an ambulance so I could have priority in triage. Instead, we waited for hours in the emergency room, which almost cost me my life,” says David.
Teri had to go home to feed the dog. When he returned, he discovered that David’s heart had already stopped twice and that he was in intensive care, on mechanical ventilation. The fever was so high that the room was as cold as possible. Doctors thought he would die at any moment.
Teri brought the whole family together. His parents, David’s parents and his brother Bob, who is a biologist and, ironically, has been studying mosquito behavior for decades.
“When they learned that David had been infected with West Nile virus, everyone asked, ‘Are you sure it’s David?’ “, explains Bob.
After all, Bob is the one who lives surrounded by mosquitoes and prefers to be in the middle of the woods to study them. “I love my subject. I’m not researching mosquitoes to exterminate them. They interest me.”
Climate change favors mosquitoes and viruses
The story of the two brothers shows how different the consequences of a mosquito bite can be: most of them are harmless and only clinical cases are taken into account, “that is to say when a person has to go to the doctor or to the hospital”, explains Bob. Or when the infection is fatal. Therefore, underreporting of people infected without realizing it is likely very high.
At the same time, the risks are real, as are the consequences. Teri was also traumatized and still cries remembering the days when her husband was between life and death.
The incident also changed Bob’s perspective.
“I would have been perfectly happy to be a mosquito enthusiast, interested in watching jungle mosquitoes fly around and do cool things,” he says. But since then, it has mainly focused on disease transmission by mosquitoes. “I became the medical entomologist I am today.”
In his job, Bob closely observes developments in the United States. For example, it took ten years for the Aedes species to spread from Southern California to San Francisco. As we know well in Brazil, these tropical mosquitoes are powerful transmitters of diseases such as dengue, yellow fever and Zika. Climate change provides increasingly better conditions for mosquitoes and tropical viruses to survive and spread to more northerly regions. “There is no reason to think that mosquitoes will come, but diseases will not.”
Mosquitoes are not dangerous, viruses are
David has changed since June 18, 2007. When he came out of the coma, he could no longer breathe or talk to himself. He was very thin and had to learn to walk again. It took him nine months to return to work. To this day, he still can’t swallow on his own.
Teri says he became more introverted, unlike the man she married. Probably because of the damage caused to his brain by the virus.
But one thing hasn’t changed: David is still frequently bitten by mosquitoes. The only thing that helps is to use plenty of repellent. “We hate them so much,” David and Teri say.
Now Bob…
“I still like mosquitoes. They’re just trying to find food and take care of their offspring. I might hate birds too, right? After all, the mosquito that infected my brother contracted the virus from a bird.”
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