US measles infections exceed 5,000 in highest surge since 1991

The United States has recorded 5,182 confirmed measles infections so far in 2026, marking the largest surge the country has experienced since 1991, according to official figures from the Centers for Disease Control and Prevention.

The new total shows the disease has spread rapidly across the nation, more than doubling the 2,289 confirmed infections logged throughout 2025. CDC figures show that 4,993 of the current infections have been connected directly to ongoing outbreaks.

Young people represent the vast majority of those infected. Children younger than five account for 18 percent of all confirmed diagnoses, while individuals aged between five and 19 represent 41 percent. Together, minors make up approximately 59 percent of the national total.

Public health specialists link the resurgence to falling childhood immunisation levels. Vaccination rates among American kindergarten students slipped from 95.2 percent in the 2019-2020 academic year down to 92.4 percent for the 2025-2026 school year. Although the United States announced that measles had been officially eliminated more than 20 years ago, drops in inoculation rates have left communities increasingly vulnerable to the highly transmissible pathogen.

The wave of infections has also ignited a federal and state disagreement regarding casualty figures. The CDC lists four deaths nationwide from measles in 2026. However, state health authorities in Pennsylvania, which is the most severely affected state with 1,487 cases, have independently documented six fatalities.

State officials in Pennsylvania define a death as measles-associated if an infected individual passes away within 30 days of symptom onset, barring an entirely unrelated cause. In August, Pennsylvania registered the fatalities of two unvaccinated patients. The CDC initially added these cases to its official federal register but later withdrew them following objections from US Health Secretary Robert F. Kennedy Jr., who questioned whether the virus was directly responsible.

The disagreement has sparked friction between Kennedy and Pennsylvania Governor Josh Shapiro. Infectious disease specialists noted to Al Jazeera that categorising deaths as measles-associated has historically been the standard measurement method employed by both the CDC and the World Health Organization. The CDC stated it is currently collaborating with the Council of State and Territorial Epidemiologists to formulate a unified national definition for recording fatalities.

Public health professionals note that the upward trend in the US reflects a wider international increase in measles cases, driven largely by vaccine hesitancy and deficiencies in health service provision. They warn that drops in local vaccination coverage can create broader cross-border risks, highlighting the international nature of disease prevention efforts.