Measles cases hit 15-year high

Four HCWs infected at work

Measles cases rose to their highest level in 15 years in 2011, yet another reminder to be on guard for the highly transmissible disease, public health authorities say.

Last year, there were 222 reported cases and 17 outbreaks. That included four health care workers who had been exposed at work, says Jane Seward, MD, MPH, deputy director of the Division of Viral Diseases at the Centers for Disease Control and Prevention in Atlanta.

One was a receptionist in the emergency department who had no documented immunity. Immunization one day after the exposure did not prevent her from acquiring measles, Seward says. One health care worker had serologic evidence of immunity and one had a history of disease, but both became infected. The fourth health care worker had no record of immunization.

The risk of transmission to patients or visitors in hospitals and other health care facilities is even greater. Last year, 15 cases were transmitted in health care facilities, Seward says.

"It's highly, highly transmissible, including through the air," she says. "Those coughs propel thousands of droplets into the air. Some of those will aerosolize and the virus will remain suspended in the air for up to a couple of hours after someone leaves the room."

Measles was eliminated as an endemic disease in the United States in 2000, according to the CDC. But large measles outbreaks continue to occur in other countries. There were more than 15,000 cases in France alone last year, says Seward. Almost all of last year's U.S. cases were linked to travel abroad or foreign visitors, CDC said.

Because measles can be severe, people with measles may visit a clinic, doctor's office or hospital — or more than one. "You can have a lot of different exposures in health care settings just from a single case," Seward says.

If there's an outbreak in a hospital, employee health will need to verify immunity of employees. People born before 1957 are presumed to be immune, but in an outbreak, CDC recommends that they receive two doses of MMR.

Seward advises hospitals to maintain good documentation on immunization and immune status of employees and to consider immunizing those born before 1957. It can be difficult and costly for hospitals to scramble to verify immunity of employees during an outbreak, Seward says.

"Some select studies have been done in health care workers showing that a small percent are susceptible. But that small percent, if they become exposed to a case, probably will become a case," she says.

"The best prevention is to be vaccinated. If you're not vaccinated then you certainly have a great chance of becoming a case if you're exposed to measles," she says.

Reference

1. Centers for Disease Control and Prevention. Measles – United States, 2011. MMWR 2012; 61:253-257.