The Microbes Are Back With A VengeanceNaomi Freundlich
In 1969, buoyed by the defeat of smallpox, polio, and other infectious ills over the previous two decades, Surgeon General William H. Stewart declared that science had won the war on microbes. Medicine, he said, should turn to fighting chronic ailments such as cancer and heart disease. It did: From 1970 to 1975, as the budget for the National Institutes of Health more than doubled, funding for infectious disease research grew by just 20%.
But in the late 1970s, epidemiologists noticed a disturbing trend. Some common bacteria--such as those that cause pneumonia and skin infections--became resistant to penicillin. Then new illnesses appeared: Legionnaires' disease, genital herpes, Lyme disease, vaccine-resistant strains of hepatitis, and AIDS. It soon became clear that victory over infectious disease had been declared prematurely.
CALAMITY. Now, thanks to lapses in immunization, even such near-vanquished germs as measles are coming back, with 25,000 U. S. cases reported in 1990, a tenfold increase in just six years. "Microbes have been on this earth for a few billion years and have learned all the tricks of survival," says Richard M. Krause, senior scientific adviser at the NIH's Fogarty International Center. Researchers say the choice now may be to spend new millions on beefing up defenses against the microscopic menace--or eventually face another AIDS-like calamity.
A small group of scientists, led by Nobel prizewinner and former Rockefeller University President Joshua Lederberg, argue that humans never did have an edge. For a decade, he and others have been clamoring for better surveillance of emerging diseases. Now, the National Academy of Sciences is worried enough about this problem to begin a study of it. "It's a pretty safe guess that we're going to have another serious viral epidemic in the future," warns Stephen S. Morse, an assistant professor of virology at Rockefeller U. in New York.
Viruses present two threats. For years, virologists have worried about an "Andromeda strain"--a mild virus that mutates into a deadly one. Such concern tends to focus on the influenza virus, which is bad enough: In 1918, the virulent Spanish flu killed 25 million people. But looking for mutant viruses, says Morse, is "sort of like preparing for visitors from outer space." Researchers are more concerned about viruses that already exist, either in isolated populations or in animals. Urbanization and changes in human behavior--such as increased travel and blood transfusions--raise the chances for these to spread.
Take dengue (pronounced deng-ee) fever. Carried by a mosquito, the virus causes headaches, rashes, and can be deadly. Dr. Donald A. Henderson, who has been nominated as associate director for life sciences in the Office of Science & Technology Policy, says dengue was a minor problem a decade ago in Asia. But urban growth coupled with a lapse in mosquito control spread it to the Caribbean and Latin America. No cases have been reported in the U. S. yet, but the mosquito that carries dengue now breeds in 18 states, mainly in the South. The pest arrived in 1985 in containers of Asian used tires that were imported into Houston to be recapped.
HOMEGROWN BUGS. Another problem is Seoul virus, a relative of a virus that in China alone causes 150,000 annual cases of hemorrhagic fever--an illness characterized by high fever and leaking blood vessels. About 12% of the rats in Philadelphia and 64% of those in Baltimore now carry the Seoul virus. In the late 1980s, researchers from the Army's Medical Research Institute of Infectious Diseases and Johns Hopkins University found that in inner-city Baltimore, 1.3% of 1,148 residents tested had antibodies to the virus, indicating exposure. None had the disease, but researchers suspect that people exposed to the virus could get high blood pressure and kidney disease later in life.
Native U. S. bugs are no less a threat. Legionnaire's disease, caused by a microbe that had been around for years, didn't turn deadly until it found its way into a prime breeding ground--central air-conditioning systems. Lyme disease was relegated to field mice and deer until a booming deer population carried it to woodsy suburbs. In Britain, meanwhile, bovine spongiform encephalopathy--the so-called mad-cow disease that destroys the animal's brain--has spread from livestock to cats, and some scientists worry about a jump to humans. Nonexistent four years ago, the disease apparently spread to cows from sheep, which suffer from a similar condition called scrapie. Ground sheep byproducts are often fed to cattle for protein, and in 1971, the temperature was lowered in the process used to make the feed. Scrapie could survive the lower heat, and, says Morse, "all the evidence favors a transfer of the agent from sheep to cows."
No one knows how many viruses are spread through transfusions and organ transplants. With sensitive new technology, researchers have discovered some viruses, including hepatitis C and E, HTLV-1, which can cause certain blood-cell cancers and brain diseases years after infection, and HTLV-2 and herpes-6, whose effects are unknown. A study last September found that 1% of 2,500 emergency room patients at Johns Hopkins Hospital were infected with HTLV viruses. "I think some of the most dangerous viruses of the future are already in us," says Dr. Edwin D. Kilbourne, a medical professor at New York's Mount Sinai School of Medicine.
Most researchers agree that new viruses will emerge more often with changing social and environmental conditions. Krause worries particularly about huge cities of impoverished people such as those found in Mexico, India, and Africa. "The closer people live together, the faster epidemics spread," he says, especially in unsanitary conditions. A complicating factor is growing mobility. In January, 1989, a Chicago man went to his mother's funeral in Nigeria. Two weeks after he returned, he was hospitalized with a high fever and internal bleeding and died within two days of Lassa fever, a rodent-borne virus that had apparently killed his mother. People who had contact with him were observed for several weeks after his death. Some were treated with antiviral drugs, and none came down with the fever.
There are ways to defend against such occurrences, many of them common sense. In the U. S., more thorough immunization can prevent measles, polio, and whooping cough, which are reappearing. And Henderson, who directed a successful worldwide smallpox-eradication program in the 1970s, is proposing a $300 million international network of 15 centers and 10 supporting labs to detect the emergence of dangerous diseases. In the 1950s and `60s, the Rockefeller Foundation set up a similar network. But it was mostly phased out in the 1970s. Had it not been, says Henderson, "I think we could have picked AIDS up earlier."
Basic research is the next best weapon. AIDS has made viruses a top funding priority at NIH. And drug giants such as Wellcome, Merck, and Glaxo have revived antiviral work. The Army's Medical Research Institute is working on vaccines for dengue fever, hemorrhagic fever, and other exotic diseases, both to protect troops in the tropics and to shield them from biological warfare. For everyone else, the best defense may be vigilance. That, say researchers, is among the best lessons AIDS has taught.
FACTORS THAT HELP VIRUSES EMERGE
URBANIZATION AND TRAVEL Help
disease travel faster and further afield
TRANSPLANTS AND TRANSFUSIONS Spread undetectable viruses
CARELESS SEXUAL PRACTICES Lead to
venereal disease, herpes, and AIDS
AGRICULTURE Exposes humans to
COMPLACENCY Leads to lapses in im-
munization and pest control