Children at a hospital in Kabul, Afghanistan, on April 18, 2022. A measles outbreak in Afghanistan killed more than 130 children since the beginning of that year. SAYED KHODAIBERDI SADAT/ANADOLU AGENCY VIA GETTY IMAGES

The number of countries battling disruptive outbreaks of measles surged to 37 last year, a report published by the Centers for Disease Control and Prevention confirmed Thursday, as officials warn that the global fight against the disease has struggled to recover in the wake of the COVID-19 pandemic. Measles can be deadly, especially in children, but it is preventable with a common vaccine.

This marks a 68% increase from 2021, when 22 countries were reporting large outbreaks, according to the new data in the CDC's Morbidity and Mortality Weekly Report. Four regions had large outbreaks, mostly in Africa or the Eastern Mediterranean.

Measles is one of the most contagious airborne diseases known to infect humans. Up to 9 in 10 people without immunity will get infected after being exposed, the CDC says, with infectious virus lingering in the air for up to two hours.

Measles can result in hospitalizations, deaths or an array of complications like blindness or brain damage.

An estimated 9,232,300 people worldwide were infected and 136,200 died from measles last year, the report's authors said. While this figure remains far lower than the more than 36 million cases estimated worldwide in 2000, it is more than a million infections larger than 2021's tally.

"It's really the accumulation of people who haven't been vaccinated against measles. The COVID-19 pandemic added an enormous amount of strain to health systems that were already struggling to deliver routine immunizations," said the CDC's Cynthia Hatcher in an interview. Hatcher is head of the agency's measles elimination team for the African region.

Just 81% of people worldwide are now estimated to have received the first dose of a measles vaccine, down from 86% in 2019. In low-income countries, vaccination coverage has plummeted from 71% in 2019 to 66% in 2022.

Hatcher spoke with CBS News from the sidelines of a World Health Organization meeting about meningitis, measles, rubella, yellow fever and tetanus in the Republic of Congo's capital Brazzaville.

"Being in this room, listening to countries about how many vaccine preventable diseases they're grappling with all at the same time, it's clear that while the pandemic may largely be over, systems have not fully recovered," said Hatcher.

Last year's sum of cases is approaching the 9,828,400 infections estimated in 2019. That year had marked a global resurgence of the virus to some of the highest levels in years, reversing decades of efforts to stomp out transmission.

Hatcher said changes in precautions and travel during the COVID-19 pandemic likely contributed to the temporary dip in cases during 2020. The massive surge in 2019 could also have temporarily blunted transmission, Hatcher said.

"A lot of people, children particularly, were exposed to measles virus, would see a level of immunity because of infection. This is obviously not what we want, because of the risk of complications and death that comes from infection," she said.

Now as cases mount, officials worry that the increase in measles could foreshadow other mounting issues stemming from gaps caused by the pandemic.

"When we're talking about measles, we're talking about a vaccine that should be delivered by the routine health system," Hatcher said, describing the uptick as a "canary in the coal mine."

"We also have to realize that these health systems are likely not delivering other essential health services," she said.

Measles in the U.S. last year
The global climb in measles cases comes as health officials have worked to reverse a yearslong decline in routine immunizations within the U.S.

Vaccination exemptions have reached the highest on record nationwide among kindergartners, the CDC reported, translating to an estimated 250,000 kindergarten children at risk of measles infection during the last school year.

The vaccine for measles, mumps, and rubella used in the U.S. — known as the MMR vaccine — is estimated to be 93% effective after one dose and 97% effective after two doses, the CDC says.

The CDC's tally of reported measles cases within the U.S. climbed from 49 in 2021 to 121 in 2022. Forty-one cases have been reported so far in 2023.

Officials had also warned ahead of this past summer of a potential resurgence in cases, as travel rebounded in the wake of the Coronavirus Pandemic. A large outbreak in American Samoa shuttered schools there earlier this year.

"There were several measles outbreaks last year, and they were all tied back to importations from countries that were experiencing outbreaks," Hatcher said.

Cases remain lower than the previous peak in 2019, which had ranked as one of the largest outbreaks within the U.S. since the virus was declared "eliminated" from the country in 2000.

Hatcher said 2019's increase within the U.S. was linked to outbreaks abroad, combined with the virus spreading into a large group that had been unvaccinated.

"In all it took was one exposure for it to really spread throughout that entire community," she said.

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