Measles is a highly contagious viral disease that can cause pneumonia, encephalitis — even death. Most often, we hear little about it because routine vaccinations have protected us from ever getting it.

A measles outbreak in the Los Angeles area of Southern California and Santa Barbara County, however, has health officials recommending the measles-mumps-rubella (MMR) vaccine as soon as possible. All it takes to spread this illness is a cough or a sneeze.

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Most of the affected people in this latest outbreak were unvaccinated.

“An outbreak is possible any place where there are pockets of unvaccinated people making up over 10 percent of the population,” said Meghan May, an associate professor of microbiology and infectious diseases at the University of New England College of Medicine.

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“Large swaths of Southern California and the Bay Area fall into this category, as do many individual counties and metropolitan areas. State health departments often post immunization rates by county, so anyone can check their local area to assess their risk,” she told LifeZette. “For example, while my home state of Maine has the highest immunization rate in the country for MMR, my home county of York has only a 79 percent coverage rate. My community is therefore at risk, while my state is not.”

The outbreaks follow a nationwide outbreak of mumps, which is also highly contagious. On Thursday afternoon alone, there were nine new cases reported at the University of Kansas.

Both diseases carry grave health risks: deafness, impaired fertility, and potentially fatal encephalitis, said May. “Rubella is a bit more complicated. Children actually tend to have a very mild illness of fever and rash and nearly always recover completely. The reason it is critical that we vaccinate against rubella is that it causes very severe birth defects if pregnant women are infected. It is exactly what we are currently worried about with Zika virus — a few decades back, we were having the same conversation about rubella.”

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In high-risk populations, the concerns for potentially fatal complications of measles, mumps, or rubella are even higher.

“These diseases are not to be thought of as trivial simply because our parents and grandparents survived them. There is a very good reason the MMR vaccine was developed in the first place,” said May.

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If you’re able to do so, get vaccinated immediately, she recommends. If your age or health status, or that of children, does not allow you to be vaccinated, a practical measure is to ensure that your physician only sees vaccinated patients.

“Patients infected with measles shed live virus before they have symptoms that can be recognized,” said May. “It may be present in waiting rooms or other common areas. If you live in an area with an active outbreak, it is also reasonable for you to ask any guests, play dates, or other contacts if they’ve been vaccinated. If they haven’t, it is critical you minimize contact. It may feel awkward, but it is so important.”