Mosquito that carries Zika virus has long, deadly history

Yellow fever wards in 1898 at an army division hospital in Jacksonville.
Yellow fever wards in 1898 at an army division hospital in Jacksonville.

This is a story about a miserable little insect that weighs about as much as a grape seed and is so puny that it probably won’t travel more than 600 feet or so in its entire life.

It is also a destroyer of armies, a poisoner of economies and a homicidal maniac that has killed more Americans than al Qaeda and the Islamic State put together. It rewrote U.S. history. It might even have invented — indirectly — the news leak, the curse of American government ever since.

Welcome back, Aedes aegypti, you tiny, blood-sucking bastard. Of the 3,500 species of mosquitoes, you’re almost everybody’s least favorite. You gave us yellow fever, which starts with vicious pain in the joints and ends with projectile vomit of blackened blood. You gave us dengue, which is also known as bone-break fever, because that’s what it feels like.

And now you’re giving us Zika, which for pregnant women, many researchers believe, can produce babies born with stunted, dysfunctional brains.

“No animal on our planet has killed more humans than that mosquito,” says Gordon Patterson, an environmental historian at the Florida Institute of Technology. “It’s an ancient saga of blood, sugar and sex.”

Patterson mentions sex because only the female aegypti sucks human blood, to feed her eggs, while the males hang out munching melons and other sweet stuff. But aegypti’s latest misanthropic rampage has a twisted sexual angle for humans, too: The government of El Salvador, fearing a Zika outbreak, has warned the country’s women not to get pregnant for the next two years. In a country where birth control is expensive and abortion illegal, that lends a whole new meaning to Just Say No.

No animal on our planet has killed more humans that that mosquito.

Gordon Patterson, environmental historian at the Florida Institute of Technology.

“That mosquito has certainly done a lot of damage over the years,” agrees Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. “We’ve been able to stop it — from the 1940s to the 1960s, the Pan American Health Organization eradicated aegypti in 18 Latin American countries and several Caribbean islands. But it requires constant vigilance.”

And a human ruthlessness equal to aegypti’s own. When dengue fever spread by aegypti started knocking out American soldiers faster than the Japanese enemy did during the 1944 U.S. invasion of Saipan — 500 a day were falling too sick to fight — their commanders blasted 25 square miles with 9,000 gallons of kerosene mixed with the super (and now banned) insecticide DDT. Aegypti lost, and then so did the Japanese.

The generals struck back so mercilessly because they knew the murderous nature of aegypti all too well. During the Spanish-American War at the end of the 19th century, aegypti-induced yellow fever killed 13 American soldiers for every one who died in combat against the Spanish army in Cuba. And unlike the Spaniards, who eventually surrendered, the mosquitoes just kept right on killing.

When U.S. commanders in Cuba refused to redeploy their troops to higher ground — hardly anyone believed, yet, that yellow fever was spread by mosquitoes, but the disease was thought to prosper in the lowlands — a subordinate officer named Teddy Roosevelt wrote a plaintive letter to the secretary of war predicting “an appalling disaster, for the surgeons here estimate that over half the army, if kept here during the sickly season, will die.” Then Roosevelt passed the letter to reporters, possibly the first news leak in American history. Orders to move the troops followed shortly afterward.

Roosevelt’s sleight-of-hand with the leak was impressive, but he would have done better to pay attention to the Cuban medical community. Nearly two decades earlier, a Cuban doctor named Carlos J. Finlay had figured out the link between Aedes aegypti and yellow fever.

“Finlay was a wonderful researcher who tried to prove that aegypti was the cause of yellow fever,” says Patterson, author of two books on combat between humans and mosquitoes. “But he didn’t know there was an incubation period for the virus. He’d have a mosquito bite somebody with yellow fever, then have it bite somebody else without the disease right away. It didn’t work because it takes about seven days with the virus before the mosquito is capable of causing an infection.”

But Finlay’s work had been noticed by an Army doctor named Walter Reed. By 1900, he was running lengthier experiments that proved Finlay right. Like Finlay, Reed also experimented on human beings — but he introduced a novel twist. The volunteer test subjects were given a $100 gold coin (an enormous sum at the time) but also a form warning them they might get yellow fever and die, one of the very first uses of informed consent in medical research. It didn’t work: when the only female volunteer, a civilian nurse, died, the public outcry forced the end of the testing program.

Reed’s work led to massive mosquito eradication programs: first, efforts to get rid of standing water in cisterns and buckets where aegypti laid eggs, then insecticides. (DDT, now reviled and banned in most of the world, won the researcher who discovered it a Nobel prize because of the millions of lives it saved.) But it was too late for any number of American cities decimated by yellow fever in the 17th and 18th centuries.

You had yellow fever everywhere from Massachusetts to Pennsylvania, and by 1798, people were dropping like flies.

Philadelphia historian Bob Arnebeck.

When yellow fever raced through Memphis in 1878, 25,000 residents fled, leaving behind a city empty of nearly everything but corpses strewn about the streets. The only reason Jacksonville’s 1888 epidemic didn’t lead to a similar exodus was that neighboring cities blocked the roads so no one could leave. Despondent city officials burned the hotel where the first victim had taken ill, and when that didn’t work, they fired cannons at random, hoping to kill whatever was carrying the disease. In a city of just 13,000, the death toll rose past 400.

Those epidemics in the south in the late 1800s were flashbacks to a similar series of yellow fever outbreaks on the east coast a century earlier. The mortality rate in Baltimore was so high that the Catholic archbishop ordered priests to stop administering last rites to the dying.

“You had yellow fever everywhere from Massachusetts to Pennsylvania, and by 1798, people were dropping like flies,” says Philadelphia historian Bob Arnebeck. “It got so bad that newspapers were talking about the end of the world and looking for clues in the Book of Revelation.

“Most of the outbreaks came in late summer and early fall, which was when ships from London — which were the lifeblood of the American economy — arrived with their cargoes. But the unloading and reshipping slowed to a crawl, and so did the economy of the whole country.”

The worst hit of all was Philadelphia, which suffered epidemics several years in row, including one in 1793, that claimed 4,400 lives — 10 percent of the city’s population.

The largest city and biggest port in America, Philadelphia had been the site of the first two Continental Congresses and the convention that drafted the constitution of the brand-new United Sates. And though a political compromise had been made that the U.S. capital would be placed in Washington, D.C., nobody in Philadelphia believed it would really happen. As construction of government buildings lagged behind schedule in Washington, Philadelphia confidently built a presidential mansion, certain the Washington plans would fizzle out.

“But the epidemic of 1793 finally put an end to that,” Arnebeck said. “Not only did the U.S. government move to Washington, but all the big-business community left for New York and even the capital of Pennsylvania was switched to Harrisburg. That epidemic changed history, literally.”

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