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Measles Makes a Comeback in the U.S.

Measles outbreaks in the United States have increased since 2019, including a spike this year, threatening the nation’s status of having eliminated the disease.

As of 4 April, the U.S. Centers for Disease Control and Prevention (CDC) have documented 113 cases of the disease since the beginning of 2024. Of these cases, 73 percent (83 of 113) are attributed to seven outbreaks, defined as incidents where three or more related cases occur.

“For comparison, four outbreaks were reported during 2023 and 48 percent of cases (28 of 58) were outbreak-associated,” the CDC said. The total number of cases in 2023 was 58.

Of this year’s cases, 50 percent occurred in children younger than 5 years old, 27 percent in people older than 20, and 23 percent in those between ages 5 and 19. Fifty-eight percent (65 of 113) resulted in hospitalizations.

Measles is one of the most contagious diseases the human race has experienced—it’s able to spread when someone with the disease breathes, coughs, or sneezes, and the virus can remain in the air for two hours.

It’s also entirely preventable thanks to vaccines, two of which are 97 percent effective and safe. In 2019, the number of U.S. cases was the highest since 1992, with a total of 1,274 individual cases confirmed in 31 states. Most of the cases in that year occurred in people who were not vaccinated against the disease.

“When measles gets into communities of unvaccinated people in the United States, outbreaks can occur,” the CDC said.

And those outbreaks can happen fast. “Approximately one infected person can transmit it to about 12 to 18 other people,” Katelyn Jetelina, a public health scientist, said on a recent podcast for Scientific American, Science, Quickly.

The CDC noted that vaccination coverage among U.S. kindergartners decreased from 95.2 percent during the 2019-2020 school year to 93.1 percent during the 2022-2023 school year, threatening a population’s herd immunity. Herd immunity, or immunity of the community at-large that prevents a disease from spreading, is achieved when more than 95 percent of the people in the community are vaccinated. The current decrease in vaccinations means that approximately 250,000 U.S. kindergartners are at risk of contracting the disease.

“Most of the recent importations involved unvaccinated Americans who got infected in the Middle East and Africa and brought the measles back to the United States,” the Associated Press (AP) reported.

The disease was officially eliminated in the United States in 2000, a status which designates that new cases of measles only occur when someone contracts the disease outside of the country and returns while still infected. “Achieving measles elimination status in the U.S. was a historic public health achievement,” the CDC said.

Before the vaccine was developed and made available in 1963, an estimated 3 to 4 million cases per year were reported among U.S. children, according to the CDC.

“Measles is still a common and often fatal disease in developing countries. The World Health Organization estimates there were 142,300 deaths from measles globally in 2018,” the CDC said.

In more serious cases, a person can be hospitalized and develop pneumonia, encephalitis, or die. “A lot of people have forgotten how dangerous measles is because of the vaccines, right? We’ve largely wiped it out, but we do not want to mess with measles,” Jetelina said.

Measles outbreaks are also occurring in the United Kingdom. The UK National Health Service is urging parents to vaccinate their children in response to 250 confirmed cases reported throughout England over the past year.

In the UK, anti-vaccine sentiments during the COVID-19 pandemic contributed to declining MMR vaccination rates, Helen Bedford, a children’s health professor at University College London, told the AP.