An infant born prematurely and infected with measles before birth has died in Ontario, Canada, according to a statement from Ontario’s chief medical officer.
Kieran Moore, M.D., M.P.H., M.Sc., said Thursday that the infant’s mother was infected and had not received a measles-mumps-rubella (MMR) vaccine. Measles may have been a contributing factor in both the infant’s premature birth and death, he said, but the child also faced other “serious medical complications unrelated to the virus.”
The infant’s death, if confirmed to be caused by measles, would be the first attributed to the disease in Canada this year.
Ontario has reported 1,729 confirmed cases of measles since Oct. 28, 2024, all tied to an outbreak that began in the eastern province of New Brunswick. Dr. Moore said there have been 140 hospitalizations and that most cases are among people who are unvaccinated or whose vaccination status is unknown.
As of June 6, the Centers for Disease Control and Prevention (CDC) has confirmed 1,168 cases in the U.S. this year, with 778 (66.6%) of those in people ages 19 and under. Experts say the confirmed number of cases likely is significantly undercounted. Most of the cases (95%) are among people who are unvaccinated or have unknown vaccination status. Three measles deaths have been reported in 2025, including two unvaccinated schoolchildren in Texas.
That state has seen the largest measles outbreak in the country, with 742 confirmed cases as of June 6, according to the Texas Department of State Health Services.
Cases have been reported in 34 jurisdictions nationwide: Alaska, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Michigan, Minnesota, Missouri, Montana, Nebraska, New Jersey, New Mexico, New York City, New York State, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Dakota, Tennessee, Texas, Vermont, Virginia and Washington.
The AAP and CDC recommend ensuring patients are covered with a two-dose MMR vaccination series. Under routine recommendations, the doses are given at ages 12-15 months and 4-6 years. One dose of MMR is 93% effective against measles, and two doses are 97% effective.
