Measles cases in the U.S. reached 141 on Feb. 13, according to information released Tuesday by the Centers for Disease Control and Prevention.
That's more cases in 44 days than are typically seen in a whole year.
Nearly all the cases are linked to outbreaks at Disneyland in California and a daycare center in Chicago. Most of those infected were unvaccinated.
While some people choose not to vaccinate their children, others are not yet old enough to take the MMR (measles, mumps, rubella) vaccine. The first dose is given at 12 to 15 months, making infants a vulnerable group.
Some people who have been vaccinated can still get the measles, especially if they have a compromised immune system.
Measles is highly contagious. It spreads through the air when an infected person breathes, coughs or sneezes, according to the CDC. It is possible to catch the measles up to two hours after an infected person has left the area.
In 2014, more than 600 people were diagnosed with the measles — the worst year since 2000, when the disease was declared "eliminated."
Measles is often brought to the U.S. from overseas, where it is more common. In 2013, more than 145,000 people died of measles, according to the World Health Organization. In 1980, measles killed an estimated 2.6 million people worldwide.
Vaccination efforts cut measles deaths by 75 percent from 2000 to 2013, saving an estimated 15.6 million lives, according to WHO.
- Measles is a respiratory virus that’s spread through coughing and sneezing.
- Measles is highly contagious. If one person has the measles, 90 percent of the unvaccinated people close to them will become infected.
- Symptoms start as a runny nose, cough, red eyes and a sore throat.
- About two or three days later, little white spots appear inside the mouth.
- Within three to five days, a rash of flat red spots spreads all over the body.
- Children younger than 5 and adults older than 20 are the most likely to have complications from measles.
- Serious complications are pneumonia and brain swelling. The swelling can cause deafness or mental retardation.
- Two in every 1,000 children who gets measles dies from it.
- Worldwide, 122,000 people die from the measles each year.
- The MMR vaccine, which covers measles, mumps and rubella, has reduced measles cases by 99 percent since it was introduced in 1971.
- The CDC recommends that children get their first dose of the MMR vaccine at around 12 months and the second dose at around 4 years.
- Even with the MMR vaccine, some people are still at risk of the measles. That includes young children who have not yet finished the MMR regimen, adults who cannot take the vaccine due to an immune system issue and those who may have lost immunity over time.
Scripps National Desk writers Mandy Gambrell, Eric Pfahler and Gavin Stern contributed to this report.