During the winter and spring of 2024, eight cases of mpox were identified among crew and passengers of four cruise ships.
The cases were associated with male-to-male sexual contact on cruise ships. Most (63%) of the eight cruise ship travelers with mpox—four out of four crew and one out of four passengers—were not vaccinated against mpox (MMWR Morb Mortal Wkly Rep 2025;74[22]:373-378).
“Cruise ship travel-associated mpox has not been previously described in the scientific literature,” said Nancy Ortiz, PhD, an epidemiologist with the CDC’s Division of Global Migration Health. “The risk of mpox for most people on cruises remains low, as it also does on land.”
Cruise Ship Cases
The first cases were reported to the CDC in late January 2024. They occurred among three unvaccinated crew members, all of whom had confirmed clade II Monkeypox virus. In February 2024, the CDC was notified of a passenger who had confirmed clade II mpox on a cruise marketed to gay and bisexual men. During March 2024, the Kentucky health department notified the CDC of a confirmed clade II mpox case among an individual who was a passenger on another cruise marketed to gay and bisexual men. The final case was reported in April 2024 among a cruise ship crew member.
Five of the eight case patients had not been vaccinated against mpox; the remainder had two shots of the JYNNEOS vaccine (Bavarian Nordic). All the cases among passengers had symptom development on the day of disembarkation or after voyage completion, making it more likely they were exposed on the voyage and were not the source of exposure.
“Cruise travelers should be made aware of activities associated with mpox spread, including sexual and intimate contact, and how to prevent it,” Dr. Ortiz added.
Preventing Mpox Spread
Dr. Ortiz highlighted that prompt onboard interventions by one ship (e.g., isolation of case-patients, contact tracing and postexposure vaccination of unvaccinated contacts) and post-disembarkation interventions by a travel company (e.g., distribution of passenger notification letters describing potential exposures) may have prevented further transmission.
Although clade II mpox cases have decreased in the United States, mpox continues to circulate at low levels, and Dr. Ortiz noted the risk for mpox is still present, particularly among men who have sex with men (MSM).
“MSM are disproportionately affected by clade II mpox,” she said. “Mpox vaccination is available and recommended for eligible people, including certain [MSM]. Vaccine can also be offered after exposure to mpox if the person has not received both doses of vaccine in the past.”
The report includes a recommendation to cruise lines to consider working with public health partners to facilitate mpox vaccination for any crew members who are recommended to get the vaccine and encourage cruise ship passengers who are recommended to get the mpox vaccine to do so before travel.
In addition, the report recommends operators of voyages marketed to gay, bisexual and other MSM consider sharing mpox prevention messaging and education before and during cruises marketed to groups of people who are recommended to get the mpox vaccine.
Dr. Ortiz reported no relevant financial disclosures.
