PATHWAY TO PERIL
Scientists worry the next devastating disease could be born where animals and humans mix in a Third World slum — then cross the globe. Zika may have been just a preview.
NAIROBI, KENYA Kenyan researcher James Miser Akoko stood at the edge of Nairobi’s vast Dandora dump in the late afternoon heat, staring down into a recipe for the next pandemic.
Dozens of men and women scoured a 30- acre garbage pit in a grim version of recycling, gathering soiled plastic toys, filthy clothing and blankets, even abandoned airline food. Large marabou storks watched over them. Free- ranging pigs, goats and other livestock grazed on refuse, marking time until the day they become food themselves — human food.
In the neighboring Korogocho slum, which shelters 150,000 of Nairobi’s poorest people, Akoko encountered a middle- aged woman laboring over a large, uncovered pot of simmering chicken intestines. These she would sell to passers- by. Dozens of marabou storks appeared, circling overhead. Residents working with bare hands and without face masks search for food and items they can resell as trash is being dumped in Nairobi’s Korogocho slum. Third World nations are breeding grounds for diseases.
“One task that is still undone for us,” said Akoko, of the International Livestock Research Institute, “is to go into the dump sites and catch the marabou
storks to see what they are carrying ... we don’t know what they are spreading in Nairobi in terms of disease.”
When scientists worry about the next big outbreak, it is places like this they mention: sprawling Third World cities, with large populations of humans and animals living together amid the squalor of dirty water and poor sanitation. Of Nairobi’s 3.4 million people, about 60% live in densely packed slums, sharing muddy roads with goats, pigs, chickens, cows and rodents.
Imagine a melting pot into which livestock, birds, flies and people all contribute bacteria and other microbes — a Petri dish for the creation of new threats to human health. Pigs, for example, act as mixing vessels for influenza. They can be infected by both bird and human flu, allowing genetic material from each to combine and form new strains.
A few years ago, researchers at King’s College London imagined how this biology might play out in a slum.
They devised a hypothetical scenario that begins with impoverished residents watching their pigs and poultry fall ill with high fevers and bleeding. Within a day, animals begin to die. Within weeks, the new influenza spreads from animals to the humans who handle them. And because the residents have lives outside the slum, working in hotels and factories, riding on buses, the influenza advances beyond the slum.
Within a month and a half, the authors wrote, “the virus has spread to nearly 80 million people worldwide. Carried abroad by international longdistance commercial flights, the illness leap- frogged out of Asia and appeared in Hong Kong, London, Paris, Marseilles, North Africa, New York, Beijing, Calcutta and Dubai almost simultaneously.”
All told, the influenza kills 140 million people. It is only hypothetical, of course, though “a plausible situation,” said Kristen Bernard, professor of virology at the University of Wisconsin- Madison’s School of Veterinary Medicine.
—— “A microbe originating in Africa or Southeast Asia can arrive on North American shores within 24 hours,” according to a 2014 report by the U. S. Centers for Disease Control and Prevention. We already see the results. Studies say a majority of U. S. cases of difficult- to- treat, drug- resistant typhoid fever can be traced to six developing countries.
The advance of drug- resistant typhoid in the U. S. has drawn little attention, especially when compared with the disease that arrived by plane in September 2014.
“The first case of Ebola diagnosed in the U. S. had major cascading effects that rippled through several industries,” said Amesh Adalja, a senior associate at Johns Hopkins Center for Health Security. “Every hospital had to augment their preparedness, public health agencies were tasked with monitoring large numbers of those returning from West Africa, airport screening tools had to be developed, and general panic from the public and politicians ensued.”
Our Ebola scare has since passed, but a longer- term problem arrived last July.
About a year after the Zika virus began storming through Brazil and most of Central and South America, the virus arrived in South Florida. The mosquitoes that carry Zika were waiting. They needed only infected people to bite, and they would find them soon enough.
“There is a huge viral reservoir in the Americas,” said José Szapocznik, a Zika expert at the University of Miami. “And we have people coming from that viral reservoir to Miami on an ongoing basis.”
—— Zika arrived last July at the peak of a humid Miami summer.
For Yessica Flores, it was a joyous time. She was pregnant.
Flores, 38, was nearly three months into her pregnancy. An immigrant from Honduras, she lives in a colorful one- story home in Miami’s Wynwood neighborhood with her husband, her mother and her 14- year- old daughter, Andrea. “I heard about Zika from the time it started in Miami,” Flores said through an interpreter. “But I didn’t bother with it.”
Watching Zika more closely than Flores was Chalmers Vasquez, the operations manager of Miami- Dade County’s mosquito control team. He believed the region was ready to combat the mosquito that carried the virus, Aedes aegypti.
On July 15, 2016, Vasquez and some co- workers stopped for lunch in Fort Myers when his phone rang.
Zika had reached Miami. That night, he and his team set their first round of mosquito traps.
—— By August, Flores was about five months into her pregnancy. One day, the lab processing her Zika test called. The voice on the other end asked questions until Flores posed one of her own. “Does this mean I have Zika?” The answer she finally got was not the one she wanted.
“I started to cry, ‘ Oh Lord.’ And then one of the women doctors told me, ‘ Take it easy, everything will be OK.’ ” she said.
As of mid- June of this year, Flores was one of 351 pregnant women in Florida to show lab evidence of the Zika infection.
—— In the days after Zika arrived in Miami, Vasquez’s team walked through neighborhoods spraying insecticides from their backpacks and searching for anything that could collect water for the mosquitoes to breed in — no bottle cap was too small.
“We found out that the insecticide that we were using in the spray trucks was no good,” said Vasquez. The mosquitos had developed a resistance to it.
After testing various compounds, they switched to naled, a potent insecticide sprayed from airplanes. Aerial treatments cut the number of mosquitoes they caught to less than half in a week.
On Jan. 27, 2017, Flores went to the school where she worked to request her maternity leave. As she was leaving, she felt an abrupt pain. A co- worker told her to go to the hospital. The baby was tested, and the doctor urged Flores and her husband to relax. At seven pounds, Baby Daniella Elizabeth Yac was healthy.
It is too early to say whether Daniella has avoided any damage from Zika. She will be monitored closely for the first five years of her life to verify that her head and eyes are developing normally.
The CDC and others continue to preach mosquito control. “So that wasn’t a small outbreak because it just fizzled out,” said Dan Strickman, senior program officer at the Bill & Melinda Gates Foundation. “It was a small outbreak because we did something about it.”