New York City health officials said Friday they are investigating an outbreak of measles that’s made at least 16 people sick.

It might be part of a bigger national outbreak linked to the Philippines.

Health officials are quick to declare concern when they see someone with measles, which is one of the most contagious human diseases. Although it was once seen as a normal childhood infection, it’s easily prevented with a vaccine. And it should be, because fully a third of patients develop complications from the virus, including pneumonia, miscarriage and brain inflammation that can put patients into the hospital or even kill them.

About 90 percent of unvaccinated people will get infected if they’re exposed to it.

New York health officials say four infected children were too young to have been vaccinated and that parents had opted not to have two others vaccinated.

Measles was considered eradicated in the U.S. in 2000, but the nation has seen a recent uptick in cases caused by unvaccinated travelers who become infected abroad. Last year, at least 175 cases of measles were reported in the U.S., according to the Centers for Disease Control and Prevention.

California has also been reporting an outbreak. As of last month, California health officials have counted 15 cases of measles in six counties.

They declared an alert when an infected college student used the San Francisco area public transit system, and he was later shown to have infected two male relatives.

Measles is a highly contagious virus that spreads when an infected person coughs or sneezes. Most people in the U.S. are either naturally immune to measles from having been infected or have been vaccinated against it.

The CDC said earlier this week they had tracked 54 cases of measles in the U.S. so far this year, including a dozen in people who had recently traveled to the Philippines.

Source: NBC news