US measles outbreak exceeds 5,000 cases as Pennsylvania infections rise

The number of measles cases reported in the US has surpassed 5,000 this year, as Pennsylvania continues to experience the country’s largest outbreak, according to public health authorities.

Figures from the US Centers for Disease Control and Prevention (CDC) show that 5,182 cases had been recorded nationwide as of 5 November, marking the highest annual total since 1991.

Pennsylvania’s Department of Health reported 1,505 confirmed cases as of Monday 9 November, an increase of 18 since its previous update on Friday. The state recorded 73 new infections over the preceding seven days.

Measles-related hospitalisations in Pennsylvania have risen to 290, while six deaths associated with the disease have been reported this year.

Children and adolescents under 18 account for approximately one-third of cases in the state, while fewer than 1% of those infected were fully vaccinated.

Nationally, 96% of reported cases involved people who were either unvaccinated or whose vaccination status was unknown.

Pennsylvania remains the worst-affected state, followed by South Carolina and Utah, according to CDC data.

The increase in infections comes as the Pan American Health Organization (PAHO) prepares to review whether the US continues to meet the criteria for measles elimination, a status it has maintained since 2000.

The outbreak is also relevant to international travel health, particularly as measles is highly contagious and can spread through international movement.

The scale of the outbreak highlights the importance of monitoring infectious disease developments and ensuring travellers have access to appropriate medical advice and care when abroad.