Blair Davis on the Hantavirus

Just An FYI:

Click to learn more about the Hiking the Grand Canyon:  The Corridor Trails video.Although Hantaviruses are newly recognized in the "new world", several strains have been known in the "old world" for a long time. The old world strains cause a different clinical presentation called HFRS (hemorrhagic fever with renal syndrome). The HFRS strains affect thousands of people in Asia & Europe every year (China reports 40,000-100,000 cases per year), and those people in the USA who were connected in one way or another to the Korean Conflict may have heard the word "Hantavirus" because both native Koreans and U.N. troups were affected by the HFRS strains.

The word "Hantavirus" in the new world is primarily connected to previously unrecognized strains and a newly recognized clincal presentation which affects the lungs and is called "HPS" (Hantavirus Pulmonary Syndrome).There have already been four strains identifed in the United States which affect the lungs, and many other strains which have not been associated with human illness. Each strain appears to be rather host (rodent) specific, and the strain causing most publicity and most human illness is called "Sin Nombre" and is primarily associated with the Deer Mouse; the Deer Mouse is found in most parts of North America except for the Southeastern U.S. Habitat studies (11 different biomes @ 13 sites) done in 1994 in Arizona found Deer Mice infected with "Sin Nombre" throughout the state, from the North Rim of Grand Canyon to the lower Sonoran desert; in other words, all over the place.

Over 270 HPS cases have been reported in the U.S., with a distribution of 31 states. HPS does not get its reputation because it affects a lot of people, it gets its notoriety from what it can do to you. Since 1994, the case fatality rate has improved, but is still over 30%. Is it worth avoiding contact with rodents? Always has been, even before we knew about HPS. The Deer Mouse is also a significant resevoir for plague and other diseases. HPS is a special problem because the body has to beat the virus, and most persons infected will require specialized hospital support systems during the process.

The CDC's All About Hantavirus web page is highly recommended.

To date there has been one case of HPS epidemiologically connected to the bottom of Grand Canyon, 31 cases in Arizona, 6 cases in Coconino County (1 fatal), with 1 case in the County this year. There will be ups and downs with Deer Mouse populations, and not all Deer mice are necessarily infected, but since they don't get sick from it, why take the chance. The virus is shed in the urine, saliva and feces of infected mice. The virus is known to have an airborne transmission, and human cases have primarily been connected to enclosed areas with poor ventilation. The virus is highly susceptible to sunlight. The jury is still out on whether or not ingestion is a possible mode of transmission; another reason to keep our food out of reach of the rodents while backpacking.

Worth taking some precautions? Odds look real good, but statistics won't mean much if you (or someone close) is the victim!

Our group encountered lots of mice (nothing new) during our Deer Creek/Tapeats Creek trip in October; perhaps that had something to do with seeing 3 rattlers on the river route?

-- Blair Davis
   December 12, 2000

Blair Davis works with zoonotic diseases in his job at the Coconino County Department of Health Services.

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