Five years ago, I spent a few days hiking in Yosemite National Park with my family. A few days after we left, the National Park Service put out a notice of an outbreak of Hantavirus – a disease transmitted by air and hosted by mice. This was the first time I had ever heard of this virus with nearly a 40% fatality rate.
The relevance of this virus to piano tuners and piano owners is that old pianos often serve a second purpose as mouse hotels. Even if you haven't seen any mice around your house, if you haven't physically opened up your piano in the past few years and checked for mice nests or droppings, there is more than a slim chance that mice live or have lived in your piano. I would say that over 25% of upright pianos that I open up show some sign of mouse inhabitation.
There is a lot of concern about Hantavirus in the piano technician community (rightly so), but I find that there is also a lot of misinformation. I'd like to try to clear things up a bit here.
First of all, the Center for Disease Control and Prevention (CDC) is the best place to get good, non-sensationalized information about this issue. Hobbyist and even professional web forums are full of hyperbole and misinformation.
Hantavirus was first recognized in 1993 in Northwest New Mexico. Since it's discovery, more than 96% of reported cases have occurred west of the Mississippi River.
Hantavirus is spread through rodent feces and urine. It is kicked up into the air when mouse droppings are disturbed and causes infection when breathed in by humans. Hantavirus doesn't seem to live long once exposed to air or sunlight. For humans to become infected, there must be an active mouse infestation. Droppings that are more than several days old are unlikely to harbor the virus.
There have been only two cases of Hantavirus with known exposure in Louisiana.
The virus is carried by several species of rodent: the deer mouse, cotton rat, rice rat, and white-footed mouse. All of these usually live in rural areas, but the deer mouse and cotton rat can sometimes be found in cities under certain conditions. House mice rarely, if ever, carry the virus. Barns, sheds, and other unattached structures in rural areas are the most common places to find the virus, and therefore require the most caution when cleaning or working in.