The US measles count has climbed to 3,659 confirmed cases, with 171 new cases added this week, according to today’s update from the Centers for Disease Control and Prevention (CDC).

Of the 3,659 confirmed cases, 18% are in children age 5 and under, 43% in children and teens aged 5 to 19, and 38% are in adults 20 and older. Nine percent of case-patients have been hospitalized. Ninety-five percent of case-patients are unvaccinated or have unknown vaccination status.

The CDC also now lists one measles death for the year, though Pennsylvania has reported four measles-associated deaths. The agency says it’s working with the Council of State and Territorial Epidemiologists to develop a standardized definition of deaths due to measles. The one death has an asterisk next to it.

“This number is subject to change; CDC will update its reporting as additional information becomes available and relevant reviews are completed,” the CDC said.

There have now been 40 new measles outbreaks reported so far this year (one new); 95% of all confirmed cases are linked to outbreaks that started this year or in 2025. An outbreak is defined as three or more cases.

A total of 5,948 confirmed measles cases have been reported in the United States since the beginning of 2025. In 2024, there were 285 confirmed cases.

129 more cases in Pennsylvania

Pennsylvania remains the nation’s hot spot, with 129 new cases in the past seven days and 890 for the year, according to an update today from the Pennsylvania Department of Health. Lancaster County, where two of the state’s measles deaths have been reported, has been the hardest hit, with 342 cases. 

Other states with notable increases in measles cases include Ohio, which added nine new cases this week and now has 189 for the year; Kentucky, which added 10 new cases and has 67 for the year; and Wisconsin, which added four new cases and has 171.

The World Health Organization (WHO) today announced the composition of flu shots for the 2027 influenza season in the southern hemisphere.

The composition of the vaccines is decided by a group of experts the WHO convenes twice a year in February and September. At these meetings, the group reviews data on circulating flu viruses generated through the Global Influenza Surveillance and Response System (GISRS) and makes recommendations for upcoming flu seasons in the northern and southern hemispheres. 

Flu season in the southern hemisphere typically stretches from April through September but can last until October or November.

In the September meeting, experts reviewed flu activity from February through August, which was dominated by influenza A(H1N1)pdm09, A(H3N2), and influenza B viruses. 

For egg-based vaccines, the WHO recommends the following:

• an A/Missouri/11/2025 (H1N1)pdm09-like virus;
• an A/Darwin1454/2025 (H3N2)-like virus; and
• a B/Tokyo/EIS13-175/2025 (B/Victoria lineage)-like virus

Recommendations for cell culture-, recombinant protein-, or nucleic acid-based vaccines include:

• an A/Missouri/11/2025 (H1N1)pdm09-like virus;
• an A/Darwin/1415/2025 (H3N2)-like virus; and
• a B/Pennsylvania/14/2025 (B/Victoria lineage)-like virus.

The group also reviews flu viruses circulating in animals to monitor for potential pandemic threats.

‘Global public health collaboration at its best’

The WHO’s director for epidemic and pandemic management said GISRS demonstrates “the power of global solidarity in public health.”

"The commitment of countries and laboratories to share data, viruses and expertise enables WHO to make timely vaccine recommendations, strengthening our collective ability to detect and respond to emerging influenza threats,” Maria Van Kerkhove, PhD, said in a news release. “This is global public health collaboration at its best."

• The Santa Teresa livestock crossing in New Mexico reopened yesterday, 18 months after it closed to contain the importation of New World screwworm (NWS) from Mexican cattle, per media reports. In announcing the reopening, US Agriculture Secretary Brooke Rollins noted that the pest has not been eradicated from the United States and that the crossing will stay open only if Mexican authorities continue to meet the terms of a joint surveillance and treatment plan. So far this year, NWS has been detected in 49 animals in Texas and New Mexico, including a recent case in a horses in Texas and New Mexico.
• Hillsborough, Pasco, and Pinellas counties in west-central Florida have declared states of emergency to battle dengue fever amid rising cases of the mosquito-borne disease, including one death, in Hillsborough. A Hillsborough emergency order is meant to allow the county to take certain actions to control the mosquito population and pursue federal reimbursement of some expenses. As of September 23, 177 dengue cases had been confirmed in the county. While case counts are low in Pasco and Pinellas counties (two and seven, respectively), the emergency will allow officials to work to prevent the disease from further spreading across county lines, WUSF reported.
• The US National Institutes of Health (NIH) yesterday launched a new artificial intelligence–informed PubMed tool designed to boost the replication and reproducibility of NIH-funded research. The tool, Linked Discoveries, allows scientists to more easily visualize how an individual research finding relates to the larger body of biomedical evidence. So far, the tool links to more than 29 million PubMed publications. 
• This week, Berlin Seeds recalled alfalfa sprout seed after one person became ill and the seed supplier notified the company that the finished sprouts were part of a US Food and Drug Administration investigation of a multistate foodborne illness outbreak caused by Shiga toxin–producing Escherichia coli and Salmonella Agona. A spent irrigation water sample from one seed lot also tested positive for E coli. The seeds were sold at the company’s store in Millersburg, Ohio, and online from February 13 to August 26 to customers in 44 states.
• The Global Polio Eradication Initiative this week reported seven cases of wild poliovirus type 1 (WPV1) in Afghanistan with paralysis onsets in August, one case of circulating vaccine-derived poliovirus type 2 (cVDPV2) in Chad with a paralysis onset in July, and three cVDPV2 cases in the Democratic Republic of the Congo with paralysis onsets in June and August. Afghanistan now has 32 WPV1 cases in 2026, compared with 21 last year.