DDT was poison, but Hawaii probably misses it right about now
We don’t really want DDT to come back — but we don’t want “break-bone fever” either
By Meagan Day
DDT is evil, right? The pesticide that was so effective in killing off mosquito populations in the 1940s and ’50s got a comeuppance in 1962 when Rachel Carson’s Silent Spring alerted the world to its environmental dangers.
But nature’s a fairly logical mother. In 1972, the US banned the domestic sale of DDT, later classifying it as a probable human carcinogen. And then, whaddya know, the mosquitoes came back stronger than ever. It’s hard to say which is the lesser evil — no one wants liquid cancer raining down on them, but we might also consider the nearly 400 million people who contracted dengue fever last year.
On Monday, Hawaii declared a state of emergency to deal with an outbreak of dengue fever on its Big Island. At 240 cases so far, it’s the this biggest US dengue outbreak since the pre-DDT era.
It is not, however, the biggest dengue outbreak in American history — that distinction goes to the Philadelphia contagion of 1780, when the suffering dengue caused led people to call it break-bone fever.
The nickname is often attributed to physician Benjamin Rush, a signatory of the Declaration of Independence, who claimed that dengue’s “most remarkable” symptom was “an uncommon dejection of the spirits.” One of Rush’s patients suggested it be called break-heart fever instead.
Dengue fever is carried by the Aedes aegypti mosquito, which originally made its home in Africa, where it bred in puddles and wreaked comparatively minimal havoc on humans.
Slave ships, it turns out, were built perfectly to harbor A. aegypti, which prefers artificial containers of water to its natural habitat, and the 17th-century slave trade brought dengue out of Africa.
“Eggs come to maturation if water splashes up against them,” said Thomas Apel, a professor of history at Menlo College. “Slave ships had more water than most ships because they were carrying so many human beings.”
So the slave ships brought over infected humans and the organisms that spread the infection. The first outbreak probably occurred on the Caribbean islands of Martinique and Guadeloupe in 1635. Another occurred in Panama in 1699. Hubs of the slave trade were especially vulnerable.
Pennsylvania passed the United States’ first-ever Abolition Act in 1780, the same year as the Philadelphia outbreak, but by then the mosquitos had already begun breeding in the city’s pails, pools and puddles.
The US saw more dengue outbreaks in the centuries that followed, but they were nothing compared to the constant barrage of outbreaks in the Caribbean and Central and South America. Increased global trade meant A. aegypti made its way to Asia, Australia and the Pacific Islands during the 19th century.
Its mortality rate was low, however, and dengue was not considered a global health threat — especially compared to Yellow Fever, an even more deadly disease carried by A. aegypti. Yes, dengue was everywhere, but no one was that concerned … yet.
When World War II began, A. aegypti again came aboard, crisscrossing the South Pacific on warships. Concerned about malaria and typhus, which are also transmitted by mosquito, the Allies began using massive amounts of DDT.
In the 1950s, the World Health Organization showered the Caribbean, Africa, Australia and Asia with the chemical. The use of DDT eradicated a lot of A. aegypti and for a time effectively masked its growing geographical footprint.
The US government, nudged by Rachel Carson and a newborn environmental movement, eventually found DDT to be unsafe for humans and discontinued its use in 1972. In the following decades the mosquitoes, which had by then quietly spread across the Earth again, returned with a vengeance — now resistant to pesticides and more ubiquitous than ever.
Consequently, dengue fever experienced a resurgence, and it hasn’t slowed down. Dengue outbreaks intensified in the 1980s and ’90s. The problem became severe when the world saw over 100 million cases of dengue fever in 1998. In 2015, the World Health Organization reported that 390 million people were likely infected with dengue, with about 96 million infections developing into clinical cases. About half of the world’s population is now at risk.
A number of complexly interrelated factors are responsible for the current spike in dengue outbreaks: poverty, global urbanization and increased transnational mobility among them. Together they are introducing new strains of the disease and catalyzing new epidemics.
Dengue is a consequence of increased contact, starting in the colonial period, among peoples of different nations. Its origins are global, and its solution will have to be as well. Ideally it won’t involve dumping buckets of poison on the Earth, but with the outbreaks growing more frequent and more deadly, you can sort of see the appeal.
