How to Keep Bats From Causing the Next Global Pandemic
In 2007, in a rural district in northwestern Bangladesh, a man fell ill with fever, followed by fatigue, headache, and coughing. His wife tended to him at home over the next four days, feeding him and wiping froth and saliva from around his mouth. When he began to have trouble breathing, a cousin and a friend rode to the doctor’s office with the patient sandwiched between them on a motorcycle. The next day, they transported him via microbus to the nearest hospital, where he quickly died. All five people in close contact with the patient in his final days soon came down with the disease, known as Nipah virus, and the wife and cousin also died.
It was a small tragedy at the other end of the Earth, and in the grand scheme of things hardly worth noting.
But a new article in the journal Antiviral Research argues that we ought to pay close attention, and not just for philanthropic reasons. Without intervention by the developed world, says Stephen P. Luby, M.D., of Stanford University, a case like this is how the next great plague could leap from wildlife and quickly turn up in our own homes. “Bring out the dead” could become the catch phrase of 2014, or 2040.
Bangladesh is among the poorest and most densely populated nations in the world, says Luby, who worked there for eight years before returning to the United States in 2012. But when he talks with people back home about poor clinical care there, and the absence of basic infection-control measures, “they see it as an issue only for Bangladesh.” Luby wrote his article to show just how deadly that sort of thinking could be.
Nipah virus was first discovered in 1998, and outbreaks now occur almost every year in Bangladesh and just across the border in India. As with SARS, Ebola fever, and a dismaying variety of other emerging diseases, Nipah virus comes from bats—in particular, the Indian flying fox, Pteropus giganteus. Luby was part of the team that figured out how the disease gets from bats to humans.
In Bangladesh, date palm sap is a favorite treat. Collectors climb to the top of a date palm tree, shave the bark, and set a clay pot underneath to catch the sap. The bats can’t ordinarily penetrate the bark, but they’re quick to adapt to a new food source and, in the course of feeding on the sap, they often leave bat urine and droppings in the clay pot. People relish the sap as a seasonal delicacy, preferably fresh and raw, and they are generally unaware of the hazard of Nipah virus until symptoms begin.
About 70 percent of victims die. But so far, says Luby, the virus is not highly contagious. It spreads via the saliva mainly to people who care for a victim. So how realistic is the threat? That is, could Nipah virus cause a pandemic?
RNA viruses like Nipah “have the highest rate of mutation of any virus or living organism,” Luby writes, enabling them to adapt readily to new environments. He likens the possibility of a pandemic to what happened with another virus in the same family: Until about a thousand years ago, an early form of rinderpest was a problem only for cattle, buffalo, giraffes, and certain other ungulates. Then a mutation occurred and the new virus jumped from domestic livestock to humans. It also became fiercely contagious. Measles, as this terrifying new disease became known, went on to kill tens—if not hundreds—of millions of people worldwide, until a vaccine brought it under control in the 1960s.
To avoid a replay of that scenario, Luby wants the governments of the United States and the European Union to invest in infection control and other preventive measures in undeveloped countries like Bangladesh. For instance, bringing a powdered detergent and proper hand-washing protocols to healthcare workers can cost less than $1,000 a year per clinic, he says. And if that keeps a more contagious form of Nipah virus from getting on a plane bound for JFK International Airport, that’s not charity. It’s an investment in the health of our own citizens.
Keeping emerging diseases under control also means working closely with conservationists, says Luby. Bats are already demonized in many places, and it doesn’t help their image when they turn out to be the host species for such deadly diseases as SARS, Nipah and Hendra viruses, Ebola and Marburg hemorrhagic fevers, and possibly the new Middle Eastern respiratory virus called MERS.
Why bats? It’s partly because they are such a diverse group, with 1,250 species, comprising about 20 percent of all mammals, says Jon Epstein, a veterinary disease ecologist with EcoHealth Alliance in New York. Some researchers theorize that immune systems or other physiological differences might make bats more likely to carry viruses. But so far that’s only a theory. The bat lifestyle of roosting together in dense colonies may also encourage viruses. These colonies often occur in and around human habitations, and the ability of bats to fly means any virus can get dispersed across a wide geographic area.
But when you see an emerging disease come from wildlife, says Epstein, “it’s generally triggered by something people have done to manipulate the environment,” meaning agricultural expansion or intensification, or urbanization, coupled with the modern tendency to move plants, animals, and people all over the world. “It’s really human activities that are driving spillover.”
Modifying human behavior also generally turns out to be the easiest and most practical way to prevent disease. In the case of Nipah virus, the simplest solution is a sort of skirt woven from bamboo and wrapped around the tree trunk, to keep the bats away from the area where the sap is being collected. As the January-February season for date palm sap approaches, the government of Bangladesh is also beginning a campaign to alert people to the danger.
Epstein tells a story about why these preventive measures matter. In Australia, Hendra virus, a cousin of the Nipah virus, also spreads from fruit-eating bats and frequently infects horses. Seven human cases have occurred there, with four deaths. A few years ago, a young veterinarian in Queensland was called to treat a horse with respiratory symptoms. When the veterinarian was hospitalized soon after with Hendra virus, he recalled that he had thought about going back to the truck to get his gloves and other safety equipment. “I just wish I’d gone back,” he said. Instead, he soon died.
“It’s one of those things where it’s never a problem,” says Epstein, “until it’s a problem.”