Welcome to the thirty-third edition of FOI Clinical. Each week, we'll send you a briefing on outbreak news. When something urgent breaks, you'll get an alert the same day.

In this edition

Measles: deaths reported – West Nile virus: California at a five-year high – Salmonella: pet turtles – Cyclosporiasis: weekly updates end – Seasonal illnesses – Dengue: Florida confirms a death – Legionnaires' disease: South Bronx – Mumps: San Diego State – Ebola: DRC

National interest

Measles: CDC records one death, Pennsylvania four

CDC's measles page, updated September 18, now lists one measles death in 2026. Last week, it listed none. The 2025 column still shows three.

The number shows an asterisk, which corresponds to a note that says the death count is subject to change as additional information becomes available and relevant reviews are completed. CDC also says it is working with the Council of State and Territorial Epidemiologists on a standardized case definition for measles deaths, intended to make classification consistent across jurisdictions. The single death is at odds with state-level tallies. Pennsylvania has reported four measles-associated deaths.

As we reported last week, CDC shifted the source of its death count from state reports submitted through the National Notifiable Diseases Surveillance System to death records held by the National Center for Health Statistics, which are filed and coded months after the event. 

State updates:

• Pennsylvania: the state dashboard reports 835 cases as of September 23, including 111 in the preceding seven days. In all, 164 people have been hospitalized. Fewer than 1% of cases were in people recorded as fully vaccinated. The four deaths announced through September 15 are included on the dashboard.
• Wisconsin: state health services confirmed 171 cases statewide as of September 22. The southwest outbreak, in Grant, Iowa, Lafayette and Vernon counties, accounts for 161 confirmed and six probable cases as of September 18. Two other cases, in Marathon and Chippewa counties, are linked to out-of-state travel and are not connected to the southwest outbreak.
• Georgia: unchanged from last week at 16 cases this year, including ten linked to a metro Atlanta daycare.
• Utah: The state has reported 527 cases year to date, including three in the last three weeks. Last year, there were 197 cases reported in the state.

West Nile virus: California at a five-year high

CDC's ArboNET data, as of September 22, reported 813 West Nile virus disease cases in 43 states, of which 607 (75%) were neuroinvasive.

California accounts for a large share. The state's surveillance dashboard, updated September 18, records 147 human cases across 21 counties, 25 of them reported in the preceding week. Also reported are 623 WNV-positive dead birds, 3,544 positive mosquito samples, 141 sentinel chickens and 14 horses. The California Department of Public Health described activity as the highest in five years in a news release from August 20, when the state had recorded 30 cases from 13 counties.