Saturday, 7 February 2015

Measles: A Tale of Two Outbreaks

WebMD Health News

Feb. 6, 2015 -- The current measles outbreak, which has topped 100 cases so far, is believed to have started at two Disney theme parks in California.

But it’s not the first time measles has been spread through a big theme park.

Two years ago, measles passed through a theme park in Orlando, FL. The grand total of cases in that outbreak? Five, including a tourist from Brazil.

Those cases got little notice. The California outbreak, on the other hand, has parents scared and angry, politicians taking stands on vaccination, and public health officials in 14 states bracing for a second wave of infections.

What made the difference? How did one outbreak flame while the other fizzled?

“Part of it, of course, is just luck. When you have patients who are infectious, it all depends on how many non-immunized people they come across. Of course, we try to make the best luck we can,” says Kenneth Alexander, MD, chief of the Division of Infectious Diseases at Nemours Children’s Hospital in Orlando.

Public health officials agree.

“I can only speculate, but I think that we have a higher vaccination rate in Central Florida compared to the areas of California affected by the outbreak,” says Tania Slade, epidemiology program manager at the Florida Department of Health. “Herd immunity likely prevented the further spread of measles in our community.”

Herd immunity means that since many people in a group, or “herd,” are vaccinated against a disease, the few people in the group who aren’t immunized also get protection from the illness. The disease won’t spread in their group since most people can’t catch it.

Slade declined to name the theme park involved since the outbreak is over, and she doesn’t want to spook visitors. Tourism is the area’s biggest industry, after all.

But as public health officials in Florida have watched the California case count climb, they've realized they were lucky. “We’re very relieved we dodged that bullet,” she says.

Comparing the two outbreaks is instructive. Both are believed to have started when an unvaccinated person visiting the U.S. from another country came into contact with the measles during a trip to a theme park. Both began over the winter school holidays in mid-December. And both sent investigators scurrying to tamp down the disease. Both were even in counties named for their famed orange groves.

source : Measles: A Tale of Two Outbreaks

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