Health authorities remain confident that the recent hantavirus outbreak linked to a cruise ship will not escalate into a widespread epidemic because hantaviruses are not known to spread easily between humans.
However, officials across multiple countries are continuing extensive contact-tracing efforts to identify and monitor individuals who may have interacted with infected passengers or those who later died.
Hantaviruses are typically transmitted when people inhale particles contaminated by rodent droppings.
Human infections are uncommon, although limited outbreaks have occurred globally in the past. The strain connected to the cruise ship incident — the Andes virus — is believed to have the rare ability to spread between people under certain conditions.
Researchers are also investigating whether the virus may have mutated.
Scientists are racing to gather more information about the outbreak, including determining how the virus spreads and whether any genetic changes have increased its transmissibility.
The primary aim of contact tracing is to notify individuals who may have been exposed, monitor them for symptoms, and reduce the possibility of further transmission. The task has proven challenging because passengers and travelers often interact with numerous people, visit crowded locations, and move between countries.
Although fewer than a dozen people connected to the outbreak are believed to have developed symptoms, only five cases have been officially confirmed so far. Health experts warn, however, that a significantly larger number of people could have been exposed.
Roughly 140 passengers remain aboard the cruise ship as it heads toward the Canary Islands, where they are expected to disembark. Authorities have not reported any illnesses among those still on board.
Meanwhile, officials are attempting to locate dozens of passengers who left the vessel nearly two weeks after one traveler died, before investigators confirmed hantavirus as the cause. Infectious disease specialists and public health officials said those passengers came from at least 12 countries, including several U.S. states such as Arizona, California, Georgia, and Texas.
Authorities in St. Helena — the remote British territory in the South Atlantic where some passengers disembarked — said they are monitoring a small group classified as “higher-risk contacts.” According to the St. Helena government, those individuals have been instructed to isolate for 45 days.
In the United Kingdom, health officials confirmed that two passengers who left the cruise midway through the trip and returned home are currently self-isolating despite showing no symptoms. The U.K. Health Security Agency added that “a small number” of their contacts are also isolating as a precaution, though none have developed symptoms.
Singapore’s health authorities said they are monitoring two men who disembarked in St. Helena before traveling through South Africa and eventually returning to Singapore. Officials stated the men, who arrived separately, are being tested for hantavirus and remain isolated at the National Center for Infectious Diseases.
The U.S. government has disclosed limited information regarding its contact-tracing operations tied to the outbreak.
Texas health officials said Thursday that public health workers had contacted two residents who left the ship on April 24. The individuals reportedly said they had experienced no symptoms and had no known interaction with infected passengers while on board. Officials added that both agreed to monitor themselves through daily temperature checks and notify health authorities if symptoms emerge.
Arizona health officials also confirmed they are monitoring another passenger who disembarked from the vessel. Authorities said the exact date of the person’s return to Arizona remains unclear. State officials noted that the U.S. Centers for Disease Control and Prevention alerted them on May 5, when monitoring procedures began. The observation period is expected to continue for 42 days.
In Canada, Ontario health officials said two returning passengers have also been advised to self-isolate since arriving home.
Alongside contact tracing, scientists are working to better understand the virus itself. The Andes virus, part of the hantavirus family found in South America, is considered one of the few hantaviruses capable of spreading between humans. Argentine officials believe the earliest infections may have originated during a birdwatching excursion in the southern city of Ushuaia.
Although Argentina’s Health Ministry has not yet deployed an official investigative team, the ministry told The Associated Press that researchers from the state-funded Malbrán Institute are expected to travel to Ushuaia “in the coming days.”
Researchers are currently examining the virus’s genetic makeup to determine whether mutations may have enhanced its ability to spread.
Scientists are also seeking to understand the precise mechanism of transmission, according to Dr. Jeanne Marrazzo, chief executive officer of the Infectious Diseases Society of America. Current evidence suggests infected individuals are most contagious while showing symptoms, and that transmission may occur through tiny respiratory particles released when a person talks, coughs, or sneezes.
