WHO says cruise-ship Andes hantavirus outbreak contained after 13 cases and three deaths

The World Health Organization said July 2 that an Andes hantavirus outbreak linked to travel aboard the M/V Hondius has been contained after 13 cases and three deaths.

WHO said all identified contacts completed a 42-day follow-up period without any additional secondary cases. The agency said the outbreak no longer posed a public-health risk and that no further related transmission was expected.

The response reached across 33 countries and overseas territories because passengers and crew, as well as people who encountered them after the voyage, were located in multiple places. WHO said the outbreak was tied to a Netherlands-flagged cruise ship, but the agency did not establish the original source or route of exposure as of July 2.

Thirteen cases, including three deaths

WHO reported 13 cases in total: 12 laboratory-confirmed cases and one probable case. Three people died, for a reported case-fatality ratio of 23%.

All identified cases had traveled aboard the M/V Hondius, according to WHO. Eight hospitalized patients had recovered and been discharged by July 2, while two remained hospitalized.

WHO said its initial epidemiological and genomic investigation found that human-to-human transmission occurred aboard the ship. That finding describes transmission connected to the vessel; WHO did not describe the event as sustained community transmission.

The outcome reported by WHO reflects the status of this identified cruise-ship-linked outbreak and the contacts located during the international response. The agency’s assessment that no further related transmission was expected followed the completion of monitoring, rather than a finding that every potential source of exposure had been resolved.

Contacts monitored after the voyage

The people identified for follow-up included passengers, crew members, flight contacts, health workers and airport personnel. WHO said 317 high-risk contacts completed monitoring, while 336 low-risk contacts completed self-monitoring.

Each identified contact completed the 42-day follow-up period. WHO reported no additional secondary cases during that period.

The differing categories reflect the response described by WHO: high-risk contacts were monitored, and low-risk contacts self-monitored. In total, the agency reported 653 contacts across the two groups. WHO identified the absence of additional secondary cases during follow-up as part of its basis for concluding that the outbreak was contained.

The case illustrates the international scope of follow-up required when people aboard one vessel continue their travel afterward. In this response, contact tracing extended beyond passengers and crew to flight contacts and people working in health care and airports, and it involved authorities across 33 countries and overseas territories.

Exposure source remains under investigation

Although WHO reported containment, investigators had not established the original source or route of exposure by July 2. The agency said genomic investigations involving samples from Chile and Argentina remained underway.

Those investigations are the next known element of the response. WHO did not provide a completion date for the genomic work or identify an original exposure source in its outbreak notice.

The distinction matters because WHO’s containment assessment addresses the identified cases and their traced contacts, while the question of how the outbreak began remained unresolved. The agency nonetheless said the completed 42-day follow-up found no further secondary cases and that no further related transmission was expected.

WHO’s July 2 update therefore provides a final public-health status assessment for the known cruise-ship-linked outbreak, while leaving the origin of exposure for investigators to determine.

Sources

• Hantavirus outbreak linked to cruise ship travel, Multi-locations, World Health Organization