Monogram

The Monogram is an official Mono County newsletter designed to provide information and updates on current issues impacting local public health. Issued at the direction of Dr. Tom Boo, MD,  Public Health Officer, the Monogram is distributed on an as-needed basis, covering pertinent public health topics, and providing valuable information and resources for visitors and residents.

Hantavirus Outbreak on Dutch Cruise Ship An Eastern Sierra Perspective

• The outbreak on a Dutch cruise ship was caused by Andes virus from South America, which is different from North American hantaviruses.
• North American hantaviruses do not spread from person to person, but Andes virus can.
• The Andes virus is likely not contagious enough to develop into a major pandemic; however, intensive international control measures and cooperation are necessary to limit the spread.
• There have been zero hantavirus cases in Mono or Inyo Counties this year. People in the Eastern Sierra should continue to take the usual precautions around rodent infestations in enclosed (indoor) areas.

An outbreak of hantavirus on a cruise ship in the Atlantic Ocean has been leading the news this week. Because our communities have lived with hantavirus for a long time, Mono County Public Health has been contacted by out-of-town media in the last few days, asking for updates on the hantavirus situation in our area. The short answer is that we have had zero hantavirus cases for about 14 months, since the virus killed three Mammoth residents in early 2025. We continue to remind people to be careful around indoor mouse infestations and believe that infection is generally preventable with simple awareness and precautions.

The cruise ship outbreak, which has so far sickened 8 people with three deaths, has been confirmed to be due to Andes virus, which is a hantavirus that differs from the type found in our area, Sin Nombre Virus (SNV). Most importantly, U.S. hantaviruses are not transmitted from one person to another, but are only acquired when we inhale virus shed by rodents (deer mice in the case of SNV), usually in indoor areas with poor ventilation. In contrast, the Andes virus, which is carried by rice rats in South America, can occasionally spread between people after it is contracted from a rice rat. Person-to-person spread is not common, but has been documented, and has caused a few outbreaks involving a few dozen people in South America, with significant numbers of deaths. While most people infected with Andes virus do not spread it to others, some do, and investigations in South America have found that occasionally one person spreads it to numerous people (so-called “super spreaders”). This is the first time an outbreak of Andes virus has occurred outside of South America. With reports of one of the ship’s passengers traveling on an airplane while ill, the May 6th report of one passenger who disembarked a couple of weeks ago becoming ill back home in Switzerland, and May 7th learning that some cruise ship passengers who debarked early have returned home to California, this is a significant public health event (outbreak). International authorities, led by the World Health Organization (WHO), are investigating the outbreak and are expected to provide more information and developments. State and local officials are monitoring the Californians who may have been exposed. In the meantime, it is my opinion that the chance of a broad global public health threat (pandemic) is low.

The response to the cruise ship outbreak will involve traditional disease outbreak investigation. People who have been on the ship or who were on the airplane with the sick individual must be tracked and monitored for the development of symptoms for around six weeks after exposure. It will be important for these people to stay at home to prevent the spread to other people. Those who become sick must be promptly evaluated and receive the appropriate level of care. With such efforts, one hopes this outbreak will be effectively contained and additional deaths prevented. While there is no specific treatment or cure for hantavirus disease, intensive care for people with hantavirus pulmonary syndrome greatly decreases the chance of death.