Measles
Highly contagious viral disease requiring roughly 95 percent vaccination coverage to block transmission chains.
measles cases in the Americas reached 53,957, with 68 deaths, by 19 September 2026, 3.8 times the same point in 2025, and new cases are now growing fastest outside Guatemala, in Peru and the United States.
Last refreshed: 4 October 2026 · Appears in 1 active topic
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Timeline for measles
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Pandemics and BiosecurityBackground
Bangladesh shows how fast measles kills once vaccination slips: it recorded 1,030 measles-related deaths by 14 September 2026 among 172,720 suspected cases, after 132 cases and no deaths in all of 2025. Its second-dose coverage had fallen to 80.7% in 2023, and no catch-up campaign had run since early 2021.
The virus is one of the most transmissible known, with a basic reproduction number of roughly 12 to 18 in an unvaccinated population. It spreads through the air and can linger in a room for up to two hours after an infected person leaves. Large crowds put unvaccinated people in close contact for hours, which is why mass gatherings recur as outbreak risks.
The MMR vaccine (measles, mumps and rubella) works in two doses, and blocking transmission takes about 95% coverage with both; below that, clusters seed in under-vaccinated pockets even where national averages look adequate. Infants too young for their first dose depend entirely on the immunity of those around them. The 2026 surge in the Americas rests on coverage gaps that opened during the COVID-19 pandemic, when routine immunisation and campaigns paused across the region.
New cases are shifting away from Guatemala
The Pan American Health Organization counted 53,957 confirmed cases in 17 countries and territories by 19 September 2026. Guatemala holds 33,866 and Mexico 12,943, but in the fortnight to 12 September the United States added 290 and Peru 190, against Guatemala's 176. PAHO flagged October's Señor de los Milagros processions and November's papal visit as risks for Peru.
The US count passed 2,231 across 42 states on 9 July, on course to beat 2025's 2,289, the worst year since 1991. It now stands at 3,471. Each long chain tests the 12-month limit that decides whether the US keeps the elimination status it has held since 2000. In late June cases reached Chester County, near World Cup host Philadelphia.
New cases are shifting away from Guatemala
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Reference
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Written with AI from Lowdown's published reporting. Not individually reviewed by an editor. Updated 4 October 2026. Editorial standards.