Here’s what you should know about measles, after a warning last week

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The warning of a possible measles exposure last week— after a bus passenger from overseas with a confirmed case traveled from New York to Boston and then to New Hampshire — was the latest reminder that the highly contagious disease still poses a risk.

Cases nationally have been rising in recent years, and 2019 is shaping up to be a bad one. Here are some questions and answers about measles.

How dangerous is measles?

The virus typically begins with a high fever, and several days later a characteristic rash appears on the face and then spreads over the body. Among serious complications, 1 in 20 patients get pneumonia, and 1 in 1,000 get brain swelling that can lead to seizures, deafness, or intellectual disability. While it’s rare in the United States, 1 or 2 of every 1,000 children who get measles dies, according to the Centers for Disease Control and Prevention.

How does it spread?


By coughing or sneezing. Someone can spread the virus for four days before the telltale rash appears. The virus can live for up to two hours in the air or on nearby surfaces. Nine of 10 unvaccinated people who come into contact with someone with measles will catch it. Dr. Anthony Fauci, infectious disease chief at the National Institutes of Health, told lawmakers at a recent hearing that the measles are “one of the most contagious viruses known to man.”

How widespread is measles?

In the United States as of Feb. 21, the CDC has confirmed 159 cases so far this year in 10 states: California, Colorado, Connecticut, Georgia, Illinois, Kentucky, New York, Oregon, Texas, and Washington. That compares to 372 cases last year.

The disease is far more common around the world — the World Health Organization said it claimed 110,000 lives in 2017. The WHO says there’s been a 30 percent increase in measles cases in recent years. Unvaccinated Americans traveling abroad, or foreign visitors here, can easily bring in the virus. A huge outbreak in Madagascar has caused more than 68,000 illnesses and 900 deaths since September.


What about in Massachusetts?

No confirmed cases of measles have been reported this year. Last year, there were two. As a Globe editorial detailed last month, , Massachusetts has a 95 percent vaccination rate — one of the highest among states. But Massachusetts allows families to receive exemptions from immunizing their children on the grounds that the vaccines violate their religious freedom. And the number of exemptions has risen sharply.

How many US children are vulnerable?

Overall about 92 percent of children in the United States have received the combination vaccine that protects against measles, mumps and rubella. Two shots are required, one around the first birthday and a second between age 4 and 6. Full vaccination is 97 percent effective at preventing measles.

Is the vaccine safe?

Yes, according to Fauci and other health officials. They point to decades of use by millions of children each year. In the late 1990s, one study linked MMR vaccine to autism but that study was found to be a fraud, and Fauci said later research found no risk of autism from the vaccine.

Source: The Associated Press, news and staff reports.