Zika fever: our newest dread disease. What is it? Where’d it come from? What do we do about it? Well for most adults, it’s a relatively mild disease — a little fever, a little headache, joint pain, maybe a rash. In fact, most people who get it don’t even know they’ve had it. But the more we find out about the Zika virus the more terrifying it becomes. For example, doctors have noticed an uptick of something called Guillain-Barré syndrome in recent outbreaks. In Guillain-Barré, your immune system attacks your nerve cells it can partially or even totally paralyze you. Fortunately, that’s quite rare, and most people recover. But if you’re pregnant when you’re infected you’re at risk of something terrible. Indeed, a child with a deformed head.
Here’s a normal baby. Here’s that infant with what’s called microcephaly. a brain in a head that’s too small. And there’s no known cure. It was actually doctors in northeastern Brazil who first noticed, just a year ago, after a Zika outbreak, that there was a peak in the incidence of microcephaly. It took medical doctors another year to be sure that it was caused by the Zika virus, but they’re now sure. And if you’re a “bring on the evidence” type, check out this publication.
So where did it come from, and how did it get here? And it is here. Like many of our viruses, it came out of Africa, specifically the Zika forest in Uganda. Researchers at the nearby Yellow Fever Research Institute identified an unknown virus in a monkey in the Zika forest which is how it got its name. The first human cases of Zika fever surfaced a few years later in Uganda-Tanzania. The virus then spread through West Africa and east through equatorial Asia — Pakistan, India, Malaysia, Indonesia. But it was still mostly in monkeys and, of course, mosquitoes.
In fact in the 60 years between the time it was first identified in 1947 and 2007 there were only 13 reported cases of human Zika fever. And then something extraordinary happened on the tiny Micronesian Yap islands. There was an outbreak that affected fully 75 percent of the population. How did it get there? By air. Today we have two billion commercial airline passengers. An infected passenger can board a plane, fly halfway around the world before developing symptoms — if they develop symptoms at all. Then when they land, the local mosquitoes begin to bite them and spread the fever. Zika fever then next surfaced in 2013 in French Polynesia. By December of that year, it was being transmitted locally by the mosquitoes. That led to an explosive outbreak in which almost 30,000 people were affected.
From there it radiated around the Pacific. There were outbreaks in the Cook Islands, in New Caledonia, in Vanuatu, in the Solomon Islands and almost all the way around to the coast of South America and Easter Island. And then, in early 2015, there was an upsurge of cases of a dengue-like syndrome in the city of Natal in northeastern Brazil. The virus wasn’t dengue, it was Zika, and it spread rapidly — Recife down the coast, a big metropolitan center, soon became the epicenter. Well people have speculated that it was 2014 World Cup soccer fans that brought the virus into the country. But others have speculated that perhaps it was Pacific Islanders participating in championship canoe races that were held in Rio that year that brought it in.
Well today, this is only a year later. The virus is being locally transmitted by mosquitoes virtually throughout South America, Central America, Mexico and the Caribbean Islands Until this year, the many thousands of cases that have been diagnosed in the US were contracted elsewhere. But as of this summer, it’s being transmitted locally in Miami. It’s here.
So what do we do about it? Well, preventing infection is either about protecting people or about eliminating the mosquitoes. Let’s focus on people first. You can get vaccinated. You can not travel to Zika areas. Or you can cover up and apply insect repellent. Getting vaccinated is not an option, because there isn’t a vaccine yet and there probably won’t be for a couple of years. Staying home isn’t a foolproof protection either because we now know that it can be sexually transmitted. Covering up and applying insect repellent does work until you forget.
So that leaves the mosquitoes, and here’s how we control them now: spraying insecticides. The protective gear is necessary because these are toxic chemicals that kill people as well as bugs. Although it does take quite a lot more to kill a person than to kill a bug. These are pictures from Brazil and Nicaragua. But it looks the same in Miami, Florida. And we of course can spray insecticides from planes. Last summer, mosquito control officials in Dorchester County, South Carolina, authorized spraying of Naled, an insecticide, early one morning, as recommended by the manufacturer. Later that day, a beekeeper told reporters that her bee yard looked like it had been nuked. Oops. Bees are the good guys. The citizens of Florida protested, but spraying continued. Unfortunately, so did the increase in the number of Zika fever cases. That’s because insecticides aren’t very effective.
So are there any approaches that are perhaps more effective than spraying but with less downsides than toxic chemicals? I’m a huge fan of biological controls, and I share that view with Rachel Carson, author of “Silent Spring,” the book that is credited with starting the environmental movement. In this book she tells the story, as an example, of how a very nasty insect pest of livestock was eliminated in the last century. No one knows that extraordinary story today.