The natural world is a reservoir for pests. At any one time, untold numbers of viruses circulate among animals. Inevitably, some will cross the species barrier, infecting people and making them sick. Scientists call such an event a “zoonotic spillover.” No one knows how often such side effects occur; presumably, animal viruses are always establishing footholds that our immune systems destroy. However, we notice when viruses spread. Today, countries around the world are seeing cases of monkeypox, a milder relative of smallpox. Like COVID-19, the disease originated in other animals. It was first seen in monkeys in 1958 before being detected in a child in 1970. Other recent infections have caused diseases such as Ebola, influenza, Lassa, Marburg, MERS, Nipah, SARS and Zika.
Dawn Zimmerman, a 51-year-old wildlife veterinarian who previously worked at the Smithsonian’s Global Health Program, has spent years studying zoonotic viruses in wildlife in Turkana County, Kenya. On a trip in 2017, she visited an area in the Northwest called No Man’s Land. “It’s because no one owns it,” she told me. “People are always fighting over that land.” On a picnic, her team might gather early in the morning to drive up the bush, sometimes accompanied by armed guards. They would check the rodent traps set the night before, taking oral and rectal swabs of any animals they found, and follow the troops of baboons, collecting droppings and sampling them. Occasionally, they would set a trap for a baboon, a cage that closes when a primate pulls on an ear of corn tied to a string, to facilitate sampling. At night, they used mist nets on riverbanks to catch bats that emerged after dark.
Sometimes the team took samples from camels, livestock animals that are known to be “viral reservoirs” or sources of potential contagion. In a town, a woman named Esther was in charge of the cattle; After tea at Ester’s house, Zimmerman’s team went out to meet the animals, bringing medicine as thanks. They hadn’t brought enough, and an owner pointed what looked like an AK-47 at them. “He just put his finger up and said, ‘No!’ Zimmerman recalled of Ester. “And he put his gun away.” To access a different site, they had to cross a river. “The first thing I asked is: ‘Are there crocodiles in this river?’ And they said, ‘No, no, totally hunted, no problem,’” Zimmerman told me. The investigators crossed as part of a large crowd, with Zimmerman pressed against his chest. That night, as they were setting up their bat nets, they saw two pairs of crocodile eyes glistening in the water.
While taking samples, researchers like Zimmerman wear N95 respirators, rubber boots, a pair or two of gloves and Tyvek suits — attire that can become unbearable in the heat. They load a container of liquid nitrogen to store their samples until they can be frozen and shipped to a lab, where researchers will screen them for viruses and then sequence the genes of the viruses to determine whether they are known or novel. In another lab, additional tests could try to predict the risk that any new virus poses to people. Over several years, Zimmerman’s data fed into PREDICT, a program run by the United States Agency for International Development (USAID) aimed at predicting, preventing, and containing emerging infectious diseases. From 2009 to 2020, PREDICT researchers collected samples from 160,000 animals and people in 30 countries and discovered nearly 1,000 new viruses. It has since been superseded by DEEP-VZN (Discovery and Exploration of Emerging Pathogens: Viral Zoonoses), a five-year program, also funded by USAID, that will spend $125 million to find new viruses in animals around the world. world. DEEP-VZN will focus in particular on coronaviruses, filoviruses, and paramyxoviruses, the three viral families that include SARS-CoV-2, Ebola, and measles. (USAID has also launched a $100 million effort called STOP Spillover, aimed at preventing and detecting side effects, based on knowledge gained from viral surveillance.) “It’s going to be a defining feature of this century, these zoonotic side effects,” Dennis Carroll, the infectious disease specialist who founded PREDICT, told me. Today, Carroll heads the Global Virome Project (GVP), another successor to PREDICT.
Vast amounts of money are flowing into these initiatives, on the theory that understanding what is out there, where it is, and how it might affect humans will help us stop side effects and respond to them more effectively when they do happen. Implicit in such efforts is an idea about how indirect effects work. They’re like ticking time bombs: identify them early enough and we may defuse them. But some scientists see the money spent on predicting indirect effects as money wasted. Spills do happen, they say, but predicting them is beyond our current or foreseeable capabilities. Pandemics, from this point of view, are a bit like avalanches: we know that somewhere on a slope a small crack will open and extend, snowballing into something monstrous, and we know that this is more likely to happen in certain areas and under certain conditions—and yet we cannot accurately predict when or where. Just as avalanches arise from an accumulation of complex mechanical and meteorological processes, pandemics occur when a knotted interplay of molecular, physiological, ecological, social, and economic conditions converge. They will always surprise us.
It could be that instead of monitoring wildlife, it is better to monitor people and catch outbreaks early, after side effects have occurred. Richard Ebright, a Rutgers University microbiologist who studies infectious diseases, has become a leading critic of the prediction approach and believes that monitoring wildlife could increase the risk of an outbreak. “The possibility that SARS-CoV-2 entered humans as a direct result of PREDICT activities, during field collection of bats and bat droppings, or during laboratory characterization of bats, droppings, cannot be excluded. from bats or bat viruses,” he said. he told me. As for whether the Global Virome Project will enhance PREDICT’s efforts, he said, “Expanding a program that was a costly failure at best would be downright insane. One could not invest research funds less wisely.”
James Bangura joined PREDICT after an Ebola outbreak in Sierra Leone in 2014. “It was horrible,” he said, of the toll from the virus. Bangura lost three friends and colleagues to Ebola. As the surveillance leader for the country’s Ministry of Health and Sanitation, he monitored the spread of the virus and won a presidential medal for his work. The following year, PREDICT began operations in Sierra Leone and he joined shortly after.
Bangura’s team, like Zimmerman’s, searched for ready-to-spread viruses in bats, rodents, and nonhuman primates, sampling 40 to 80 animals during a typical two-week trip. In 2016, they discovered a new type of Ebola virus that wasn’t hiding in caves or forests, but in people’s homes: Four bats were found in three small villages a dozen miles apart, in the district from Sierra Leone’s Bombali, were hosts to what would eventually be called the Bombali ebolavirus. Whether it will make people sick or travel between them remains uncertain: there are no known cases of human infection. “Seeing a new type of Ebola was a great satisfaction for me in my career,” said Bangura. After the discovery, “the energy was there: ‘OK, let’s look for more viruses.’ In 2020, Bangura’s team reported the first discovery of Marburg virus in West African bats. Including the current outbreak, fifteen Marburg infections have been recorded; the largest, which occurred in Angola in 2004-05, killed 90 percent of the 252 people known to be infected. After the two Bangura discoveries, PREDICT mounted a public information campaign about the dangers of interacting with bats and increased virus sampling in animals, measures aimed at preventing contagion.
PREDICT has created a hotspot map indicating where zoonoses, including coronavirus infections, are likely to occur. (Other groups, including researchers at Oxford and the EcoHealth Alliance, an NGO that studies emerging infectious diseases, have created similar maps for other viruses.) These maps are extrapolated from past contagion events and ecological factors associated with them. One thing they look at is the distribution of animal species. Bats are a logical place to look if you want to predict side effects. SARS-CoV-2 almost certainly came from bats, perhaps reaching humans through an intermediary animal, such as a pangolin, much like the coronaviruses that cause SARS and MERS. “Bats, for some reason, seem to be very good hosts for the coronavirus,” Timothy Sheahan, a virologist at the University of North Carolina, told me. Some researchers have suggested that, to help their bodies cope with the stress of flight, animals have evolved to suppress inflammation, making it easier for them to tolerate viral infections without developing disease. Tracey Goldstein, a comparative pathologist at the University of California, Davis School of Veterinary Medicine who served as PREDICT’s lab director, said the project’s enumerators tended to find some new coronaviruses within each species of bat they surveyed.
Source: www.newyorker.com