I did a paper on viruses in high school and I remember being particularly bothered by hantavirus (hantavirus pulmonary syndrome or HPS), even more so than by any of the various Ebola strains, because of its prevalence in the USA. I wanted to take this opportunity to dig a little bit deeper into what hantavirus was, how it was spread, and its impact on people.

HPS is a fairly new disease. The first outbreak that really gave rise to headlines was in the summer of 1993 in the Four Corners area when five young, healthy people died of it. The first known victim of HPS was a 38-year-old man who died in 1959. Hantavirus is spread by mice, particularly deer mice, and the explanation for the 1993 outbreak was the huge increase in mouse population (greater mouse density amounted to greater chance of human-mouse contact, and therefore greater likelihood of the disease being transmitted) caused by heavy rainfall and therefore a bumper crop of grains which gave mice plenty to eat and led to their rapid reproduction—a tenfold increase from May of 1992 to May of 1993.

Hantavirus doesn't affect the rodents which carry it. These rodents include deer mice in the southwestern states, cotton and rice rats in the southeastern states and white-footed mice in the northeastern states. The virus is expelled through urine, droppings, and saliva of rodents—it can't be spread person-to-person in the same way that many other pulmonary diseases can be. The disease is mainly spread when the virus becomes airborne when dried droppings or urine are stirred up, most commonly by the simple act of sweeping a dusty corner. There is also a possibility that the virus can be spread by bites from infected rodents and by ingesting contaminated food.

People at greatest risk for contracting HPS are those living in areas of high rodent populations and who are cleaning places such as cabins, sheds, barns, and garages which haven't been used by people for a time, especially in rural settings. It's basically a good idea to take precautions whenever performing such activities to minimize the risk of contracting hantavirus. Some HEPA-approved masks provide limited protection from hantavirus, but the virus is small enough to get through most filters. The best prevention method is eliminating rodents from the immediate area and thereby preventing the presence of the virus rather than attempting to rectify the situation later. Sealing up gaps in the home, placing rodent traps in areas where rodents might be trespassing, and not keeping food items (including bird and grass seed) where they're accessible are good, basic preventative measures.

The symptoms of hantavirus include fatigue, fever, and aches in the thighs, hips, and back. Sometimes the symptoms also include headaches, dizziness, chills, and abdominal problems. Later symptoms of the disease include coughing, shortness of breath, and inability to "fill" the lungs with oxygen (caused by the lungs filling with fluid). Treatment is non-specific and is therefore supportive—intubation, oxygen therapy, and anti-inflammatory drugs help, and the sooner a patient is taken to intensive care, the better their odds of recovery. The mortality rate for hantavirus is 50%, making it a serious illness. With most viruses, people with weakened immune systems have a higher risk of contracting the disease; hantavirus is virulent enough that even young, healthy people who aren't immunocompromised are just as susceptible as older people with more fragile immune systems.

As of right now, hantavirus has been found in roughly half of the states in the USA as well as in South America and parts of Canada. This makes it a panhemispheric disease; so far, hantavirus hasn't been found on other continents.

What strikes me as particularly interesting about hantavirus is that it isn't a more common household name. I think most of us grow up knowing that there's something "bad" about mouse droppings (rather than just the general distaste over the fact that they're droppings) but hantavirus isn't something we learn about, whereas things like Lyme disease and West Nile Disease/West Nile Encephalitis are things everyone knows about. I suppose part of that is the relatively small number of cases that have occurred—roughly 2,600 as of May 2003—and another part may be that it's a rural disease and therefore not given the same type of attention that a more urban disease (such as West Nile Encephalitis, which first showed up in New York City) might get. Another factor might be that HPS isn't spread from person to person, but neither are Lyme or West Nile. All in all, I think it's an important disease to be aware of, and one that should be treated by name. The more it's de-mystified and explained, the better a chance that less people will contract it in the future.

http://www.cdc.gov/ncidod/diseases/hanta/hps/index.htm: The CDC (Centers for Disease Control) site on hantavirus.
http://www.doh.wa.gov/topics/hanta.htm: The State of Washington Department of Health site on hantavirus (a bit more state-specific information).
http://www.hantavirus.net/: A general website with some supplementary information as well as a few more numbers, though the CDC site is more thorough.
http://www.nlm.nih.gov/medlineplus/hantavirusinfections.html: The MediaLine Plus site, a bit more medicine-intensive/healthcare-oriented.