Welcome to the twelfth 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 - Mpox (domestic) - Chikungunya - Coccidioidomycosis- VRSA in North Dakota - Petting zoo cryptosporidiosis in Rhode Island - Multi-state Salmonella Saintpaul - Rare disease reports - Mpox (international) - Avian influenza
National interest
Measles
National measles continues its slow deceleration. The big milestone this week is in South Carolina.
- South Carolina: The Upstate outbreak was officially declared over on April 27, 42 days after the last outbreak-associated case. The final count stands at 997 cases and at least 21 hospitalizations, centered around Spartanburg County, with the vast majority in unvaccinated children.
- Utah: Now the state with the most active measles transmission in the country. The outbreak reached 625 cases as of April 28 (of which 428 have been recorded in 2026). The Southwest Utah health district near the Arizona border accounts for the largest share (260 cases), followed by Utah County (97) and TriCounty (71). Of those diagnosed, 531 (85%) were unvaccinated and 51 have been hospitalized. What started in small communities with low vaccination rates along the Arizona border has spread to every corner of the state. Since the outbreak began, MMR vaccine administrations in Utah have increased 31%. State kindergarten MMR coverage (88.6%) remains well below both the national average (92.5%) and the 95% herd immunity threshold.
- California: 46 confirmed cases this year.
- Texas: 180 cases this year as of April 22.
- Oregon: 2 new confirmed cases bringing the total up to 22 for the year.
The U.S. measles elimination status will be reviewed in November. No measles-related deaths have been confirmed in 2026, but 98 patients have been hospitalized (6% of cases). Among all cases this year, 92% are unvaccinated or have unknown vaccination status.
Mpox
Mpox activity continues to track above last year. Through the week of April 18, there have been 478 cases reported nationally, compared to 282 at the same point in 2025, a 1.7x increase. Six cases were reported the week of April 18.
California remains the epicenter for domestic clade II transmission, averaging 14.5 cases per week, up from 5.8 in 2024 and 3.4 in 2025. CDPH is strongly encouraging vaccination for high-risk Californians, following a clade I case in San Francisco in an unvaccinated resident who was hospitalized after close contact with an international traveler.
CDC continues to assess the risk to the general population as low, and to men who have sex with men (MSM) as low to moderate.
Chikungunya update
Chikungunya is running ahead of seasonal expectations. National year to date cases reached 147 through the week of April 18, well above the prior-year pace, with Florida accounting for 135 (92%). Weekly cases rose to 3, against a near-zero historical baseline for this point in the year. The ongoing Cuba outbreak continues to drive travel-associated cases into South Florida. Miami-Dade County confirmed one locally acquired case earlier this year and remains under a mosquito-borne illness alert as temperatures rise. As mosquito season begins, the risk of additional local transmission increases. The FDA-approved IXCHIQ vaccine is available for travelers to endemic areas.