CLAIM: Polio stopped spreading when the pesticide DDT stopped being used, not when vaccines for the virus were introduced.
THE FACTS: Polio and its side effects, including paralysis, have been widely demonstrated to be caused by the polio virus, not a pesticide, several medical experts confirmed to the AP. Social media users are misidentifying the cause of the viral disease, suggesting that a toxic agricultural pesticide is linked to the illness. But medical experts who study the disease say there’s no truth to this claim.
“Polio vaccines [both injectable and orally-administered] are the singular reason for the decline in the incidence of paralytic polio both here in the United States and across the globe,” said Dr. Olakunle Alonge, a professor in the Department of International Health at Johns Hopkins Bloomberg School of Public Health.
The viral disease, which mostly affected children, was once one of the nation’s most feared diseases. While some people exhibit flu-like symptoms, or no symptoms at all, severe cases can cause paralysis. Vaccines became available starting in 1955, and a national vaccination campaign cut the annual number of U.S. cases to fewer than 10 in the 1970s, according to the U.S. Centers for Disease Control and Prevention.
In 1979, polio was declared eliminated in the U.S. That’s because of the wide administration of vaccines to fight the disease, emphasized Rosemary Rochford, a professor of immunology and microbiology who is the co-director of the University of Colorado medical school’s climate and health program. “The polio vaccine was directly responsible for the elimination of polio in the US,” she wrote in an email to the AP.
Meanwhile, DDT is an agricultural insecticide that was commonly used in the mid 1900s. It was banned by the U.S. Environmental Protection Agency in 1972 amid concerns about its adverse effect on the environment and its persistence in the food chain. It is also considered a possible carcinogen by the CDC. While historical accounts show that DDT was in some cases sprayed in towns in a misguided attempt to prevent the spread of the polio virus, this campaign was not effective.
“Polio the disease is caused by the polio virus,” Rochford wrote in an email to the AP. “DDT is a pesticide, so not clear how a pesticide could cause a viral infection. There is no mechanism that I know of that would have a pesticide cause an outbreak of polio.”
Alonge said the “misinformation” might be linked to some research that showed DDT may be associated with neurological effects, including leg paralysis, among those chronically exposed to high levels of the toxin. However, Alonge clarified that the paralysis caused by polio and the paralysis potentially caused by the pesticide are distinct and caused by different mechanisms. Alonge pointed out that those affected by paralysis from chronic DDT exposure don't match up with the population most affected by polio, either. Complications from DDT mainly affect farm workers, he said, not children in the general population.
— Associated Press writer Sophia Tulp in New York contributed this report.