Pandemiology Watch (April 29-May 5, 2026).
Emerging outbreaks
The World Health Organization (WHO) is investigating a cluster of hantavirus cases linked to a cruise ship traveling in the Atlantic Ocean. As of May 4, 2026, seven cases have been identified, including two laboratory-confirmed infections and five suspected cases. Three people have died, one patient remains critically ill, and three others have reported mild symptoms. Passengers developed severe respiratory illness, including fever, gastrointestinal symptoms, pneumonia, acute respiratory distress syndrome and shock. According to WHO, hantaviruses are mainly transmitted to humans through contact with rodents or their urine and feces. Infection can also occur through inhaling virus particles in the air. Human-to-human transmission is considered rare. WHO said investigations are ongoing to determine where exposure occurred and currently assesses the overall public health risk as low.
Measles
US
As of May 1, 2026, the United States has reported 1,814 measles cases so far in 2026, according to the Center for Disease Control. In 2026, the age group 5-19 accounts for 51% of the cases (928), and children under 5 years account for 21% of the cases (388). Of the cases reported in 2026, 92% were unvaccinated or had an unknown vaccination status and 6% of the cases have been hospitalized (105). A total of 4,120 measles cases and three deaths have been reported to date.
According to CIDRAP on May 1, 2026, measles outbreaks continue to spread across several US states, with Utah and Arizona reporting new infections this week. Utah added 18 new cases, bringing its 2026 total to 428 cases, while Arizona reported two additional infections, increasing the state’s case count to 93. The US Centers for Disease Control and Prevention (CDC) has recorded 1,814 confirmed measles cases so far in 2026 across 37 states and New York City. Around 93% of cases are linked to outbreaks. Health experts warn that declining vaccination rates are contributing to the resurgence of measles.
Canada
As of May 4, 2026, Canada has reported 944 measles cases in 2026, according to the Public Health Agency of Canada. In 2026, 6o% of the cases occurred in children (565). Manitoba accounts for 61% of the cases (579), and Alberta accounts for 31% of the cases (290) reported so far in 2026. 87% of the cases reported in 2026 were unvaccinated (825), and 6% required hospitalization. A total of 6,369 measles cases and two deaths have been reported to date.
Influenza
According to the Centers for Disease Control and Prevention on May 1, 2026, 155 pediatric influenza deaths have been reported in the United States during the 2025-2026 flu season. In the latest weekly influenza surveillance report, six additional child deaths linked to influenza were reported. 85% of the children who died were not fully vaccinated against influenza.
H5N1
As of May 5, 2026, the Centers for Disease Control and Prevention has not reported any cases of person-to-person transmission of H5N1 in the United States. The total remains at 71 confirmed human cases and two deaths.
Mpox
From April 19-May 5, 2026, there have been no significant updates on mpox outbreaks worldwide.