At least 41 cases of measles have been reported in the U.S. across 16 states so far this year,marking one of the steepest increases in the recent history of the virus.
Experts worry the country could face a repeat of 2019's massive surge, which authorities at the time said could threaten the U.S.'s status as having eliminated the virus.
The Centers for Disease Control and Prevention say we are seeing measles cases rising for two main reasons: More travelers get infected abroad and bring it back to the U.S., and more spread in communities with pockets of unvaccinated people, and both are happening now.
"We could expect to see more and more of these cases,” said Dr. Peter Chin-Hong, professor of medicine and infectious disease physician at the University of California in San Francisco.
Measles symptoms usually begin 10 to 14 days after exposure. They include runny nose, coughing, red and watery eyes, small white spots inside the cheeks, and rashes. The CDC says about 1 in 5 unvaccinated people who get measles are hospitalized, and it can cause brain swelling, pneumonia, and even death.
Meanwhile, health officials continue to prepare doctors to see more cases and urge parents to vaccinate.
At least 95% of a population must be vaccinated in order to meet "herd immunity" for measles — when enough people are immune and protect those who are not.
"Measles is the canary in the coal mine. We're reversing progress over the last decades and turning back the clock on so many of these childhood diseases,” said Chin-Hong.
The measles vaccine has been around since the 1960s. Doctors recommend the MMR shot — measles, mumps, and rubella — in two doses. The first dose is administered between 12 and 15 months old, followed by the second dose between 4 and 6 years old. It's 97% effective in protecting against measles and lasts for life.
CDC warns of 'imported' measles as US deals with cases
The U.S. Centers for Disease Control and Prevention is concerned about the upcoming spring travel season spreading the airborne disease.