The American Plague - Molly Caldwell Crosby [110]
Ninety-three percent of the countries in West Africa now have cases of yellow fever—up 30 percent just since the mid- 1990s. Yellow fever, it seems, is making a comeback; it is also spreading to areas that have never before seen the virus. Thirty-three countries in Africa and nine in South America are now known to house the virus. The number of deaths vary, but in South America, mortality rates from yellow fever have been as high as 80 percent. Two hundred thousand people worldwide are infected each year, but the number of actual cases is thought to be 10- to as much as 250-fold higher due to underreporting or misdiagnosis.
At one time in history, there were several factors in play that led to recurring, explosive epidemics of yellow fever. They were modes of transportation, populations of vulnerable hosts, warm weather cycles and the colonization of Aedes aegypti in urban environments. The circumstances today in Africa and parts of South America mirror those of Memphis in 1878—there is poverty, people living in shanty houses, poor sanitation, containers of water in place of plumbing, a tropical atmosphere and a high population of Aedes aegypti mosquitoes. As the human population increases rapidly, so does the number of nonimmune people. And just like the paddleboats and trains of the nineteenth century, we now have shipping containers and airplanes. Global warming has broadened the range of disease-carrying mosquitoes. And we have a new threat: Yellow fever is listed among the pathogens that might be used during a bioterrorist attack.
Will urban outbreaks of yellow fever become more widespread and more deadly? If recent statistics are any indication, they will. Africa and South America are already moving in that direction. And unlike a virus such as smallpox, yellow fever is passed between insects and animals—it can never be eradicated because nature itself gives the virus sanctuary. Migration of humans closer to jungles and forests will place people and the virus at even closer range. But with education and routine vaccine use, the outbreaks could be contained and infect fewer people. Programs are already under way to include yellow fever in childhood vaccines in Africa.
Science is also looking for ways to understand the virus better. Recent studies have unraveled some of the mystery as to how a virus like yellow fever interacts with the human immune system. In one study, scientists identified the protein on the virus coating that interferes with the immune response. In another, scientists located part of the viral protein that human antibodies lock onto to defeat it. Isolating and reproducing that protein could lead to a safer vaccine against yellow fever.
The likelihood of the American plague returning to the United States is anyone’s guess. In a 1996 article in the Journal of the American Medical Association the author wrote: “Because A aegypti mosquitoes are once again established in urban areas . . . there is widespread concern that yellow fever could erupt in explosive outbreaks, which could also occur in the southeastern United States.” But we are certainly better off than people were 150 years ago. We have a vaccine. We have modern amenities like air-conditioning instead of open windows, cars instead of open-air wagons. We have insect repellent. And best of all, we have the knowledge that the virus is spread by mosquitoes.
Still, viruses have taught us one thing throughout history, and it is this: That their will and ability to survive may be stronger than ours.
EPILOGUE
Elmwood
Of course there are elms at Elmwood, though they were planted after the fact to complement the name. Their massive, gnarled trunks rise high above the earth, and their roots spread deep beneath the ground, branching out amid the bones. There are also oaks. And there are magnolias with hard-shell leaves curling