The United States is grappling with a significant increase in measles cases, U.S. health authorities have said.

The number of infections in early 2025 has already exceeded the entire 2024 total, according to the latest data from the U.S. Centers for Disease Control and Prevention (CDC).

As of March 28, 2025, the CDC reported 483 confirmed measles cases across 20 states, among them 2 dead and 70 hospitalized, while only 285 cases were reported in 33 states during the entire year of 2024.

Texas is experiencing the most severe outbreak. 400 cases have been identified since late January, and 41 of the patients have been hospitalized, according to the Texas Department of State Health Services.

The outbreak has turned deadly. "There has been one fatality in a school-aged child who lived in the outbreak area. The child was not vaccinated and had no known underlying conditions," the Texas health authority said in a statement on March 25.

The resurgence has spurred health warnings and urgent vaccination calls, with most cases nationwide linked to unvaccinated school-aged children.

Declining vaccination rates appeared to be driving the surge in cases. The CDC reported that kindergarten measles-mumps-rubella (MMR) vaccine coverage has fallen from 95.2% during the 2019-2020 school year to 92.7% in 2023-2024, "leaving about 280,000 at risk."

"The current outbreak is absolutely being driven and started by unvaccinated individuals," CNN quoted infectious disease epidemiologist Michael Mina as saying.

The New Jersey Department of Health said that "95% of the cases reported in the United States for 2025 are among children and individuals who had not received the MMR vaccine or have unknown vaccination status."

"If a measles outbreak continues for a year or more, the United States could lose its measles elimination status," the CDC said.

The United States declared measles eliminated in 2000, meaning there was no continuous disease transmission within the country.