LONDON — As the globe heads toward the biggest outbreak of cholera in half a century, experts say cholera is very unlikely to spread to the United States or Europe because it is most likely to be spread by infected travelers.
In other words, the world’s worst cholera outbreak this century is unlikely to spread to America.
At least 400,000 people are currently infected, almost 50,000 have died and the disease has been confirmed in nine African countries. Only a few previous epidemics have outpaced this year’s toll, experts say.
Epidemiologists say the illness is spread through contaminated food or water, and travelers would likely be the first victims — a pattern that has been seen repeatedly in past outbreaks.
“There have been outbreaks where people have spread the disease accidentally,” Dr. Rosemary Morgan, deputy scientific director of the World Health Organization’s Western Pacific Region. “But this has not happened in any recent outbreak.”
Given the outbreak’s escalation and its vast geographic scope, analysts have speculated that the disease could then easily mutate into a super-strain that could wreak havoc.
Two super-flu viruses, H5N1 and H7N9, were able to spread easily between humans, for example, but their emergence was limited because they evolved over long periods of time into milder forms of the virus.
Experts say it is difficult to predict such a scenario.
“It’s absolutely impossible to know exactly what is going to happen because nothing like this has happened in the history of cholera and infectivity,” said Dr. Antonio Iannazzi, a virologist at Interflora, a firm that specializes in cholera.
Cholera is typically fatal in as little as seven days, although complications such as dehydration can weaken victims more quickly. The infection can spread via diarrhea and vomiting, and infected people in Africa and Asia routinely bathe to wash away the bacteria.
The strain now ravaging the world’s poorest countries is a particularly virulent one, with explosive outbreaks that have forced hundreds of thousands of people to flee their homes.
“We need to be aware that we are living in a world where we are not safe,” said E. O. Wilson, a Nobel Prize-winning biologist. “Cholera will never have a happy ending.”
If any cases do become contagious, experts say cholera is most likely to spread from Africa to Europe and from there to North America.
And even if it did, it would be hard to spread beyond one continent because of modern medicine and sanitation and the fact that it usually occurs near where people live.
“You would need something like a world economic system collapse and everything involved,” said Mark Ross, a geneticist at the World Health Organization’s Africa Center for Emerging Infectious Diseases. “I don’t think that’s going to happen.”