Largest U.S. Outbreak of Measles in 15 Years

At the annual Infectious Diseases Society of America conference, held last week in Boston, the Centers for Disease Control and Prevention reported that the United States is in the midst of the largest measles outbreak in 15 years. The US generally sees between 60 and 70 cases in a year; in 2011, the CDC has already recorded 214 cases.

All of the 214 measles cases can be traced back to specific imported cases because measles is no longer endemic in the United States. In 2000, a group of experts declared measles to be eliminated from the country. Disease elimination is defined as reduction to zero of the incidence of a specified disease in a defined geographic area as a result of deliberate effort. In practical terms, this means that measles is no longer circulating within the nation’s population; all recorded measles cases can be traced back to an imported case—someone who was infected in a foreign country where measles is still common.

When a person carries measles to the US from abroad, they may come into contact with people who have not been vaccinated, potentially launching an outbreak. Overall, vaccination coverage in the US is around 90 percent, but there are pockets in the population of unvaccinated people who are at risk of infection. With such a low percentage of the population at risk, the situation may not sound alarming but even a small outbreak can be quite costly. For example, a recent outbreak in Utah of just nine cases represented a cost of $300,000 in response through medical care and vaccination campaigns.

Measles is very contagious and while the disease itself often does not have lasting effects, the complications can be severe and deadly. Because the disease is still common in many parts of the world and with increased ease in global travel, it is of utmost importance for the United States to maintain high vaccination levels.

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