An infant has died of measles in Wisconsin, the state's first death from the disease in more than three decades, the Wisconsin Department of Health Services said on Thursday, Bloomberg reported via Mint.
It is the third US measles death within the last week, matching the number for all of 2025. In the 25 years before that, the US typically had no measles deaths.
"Any death of a child is a tragedy and even more so when it is related to a vaccine-preventable disease," said Wisconsin Health Secretary Kirsten Johnson.
How far it has spread
At least 45 states have reported infections, for a total of 4,852 cases, according to the Centers for Disease Control and Prevention. Contagion Live reported that the total, as of October 29, is more than twice the 2025 figure.
This week, Pennsylvania confirmed a sixth death and New York reported its first. The CDC has confirmed only four of this year's deaths and is working on a national definition of a measles death.
In Wisconsin, the virus has spread in the southwest, and nine people have been hospitalised. Health workers have given more than 42,000 doses of the measles, mumps and rubella vaccine since August.
Why it matters
Measles spreads as vaccination rates fall, weakening the herd immunity that protects infants and others who cannot be vaccinated. Two doses of the MMR vaccine are 97% effective, and one to three in 1,000 infected people are likely to die, according to the CDC.
The US has long held measles-eliminated status. An outside group of experts is due to meet next week to review whether the country has seen continuous transmission for more than 12 months, which would put that status at risk.