Hantavirus Pulmonary Syndrome (HPS) is an infectious respiratory disease endemic to North and South America. It is caused by a virus generally known as the hantavirus. While the disease is frequently fatal, is can be very easily prevented.

The hantavirus has a reputation for being a "rare" virus, which is a clear misunderstanding. In the United States, the virus is ubiquitous, being found in over half of the lower 48 states. In fact, cases of the disease have occured in at least thirty states.

The disease itself is considered rare, as the virus is not very infectious except under certain circumstances. As such, when someone contracts HPS, the incident is frequently considered to be a random "freak accident".

In this regard, contracting the hantavirus is very similar to being struck by lighting: (a) it doesn't happen very often, (b) it is worth avoiding, and (c) it can be prevented very easily if you understand how it works.

A "hantavirus" belongs to a group of RNA virii related to the family Bunyaviridae and, depending on its nature, may be the etiological agent for one of two acute illnesses: hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS). The HFRS-causing hantavirii are endemic to east Asia, while HPS-causing hantavarii are endemic to the New World. But like all virii, their distributions are only dictated by the range of their natural hosts.

There are dozens of types of hantavirii, being carried by rodents all around the world. However, the majority of these strains of hantavirus do not cause disease in humans.

The hantavirus was originally discovered in Asia, during the Korean War. Technically, it was discovered vicariously, through the discovery of the disease it caused: hemorrhagic fever with renal syndrome (HFRS). The actual virus wasn't isolated until 20 years later, in 1976; it was discovered in a striped field mouse that was trapped near the Hantaan River in Korea. This prototype virus was thusly christened the Hantaan Virus. This virus was eventually classified under its own genus, "hantavirus", when others forms were discovered in rodents throughout Asia, even extending into Eastern Europe and Scandinavia.

Americans had no reason to fear the hantavirus until mid-May of 1993, when several healthy young members of the Navajo Nation in New Mexico died within a short period of time. Their cause of death was a mystery, enigmatically described by health officials as "unexplained adult respiratory distress syndrome" (ARDS). This cluster of peculiar, unexplained deaths caught the attention of the world, prompting a research endeavor of remarkable haste. The effort involved numerous health agencies, including the Centers for Disease Control and Prevention (CDC), the Indian Health Service (IHS), the University of New Mexico, the Navajo Nation Public Health Center, the New Mexico State Department of Health, and the Office of the Medical Investigator (OMI).

On June 3, as the death toll of the Four Corners epidemic reached twelve, researchers made their critical discovery: this infectious form of ARDS created antibodies that were also produced by the hantavirus, even though no known forms of hantavirii produced respiratory distress, or were believed to exist in North America. While many researchers were skeptical of this claim, the identification turned out to be correct; this alone enabled health professionals to accurately diagnose cases of the disease before conditions became extreme, and it helped epidemiologists determine the virus' natural hosts with relative ease.

The Four Corners outbreak occurred because of a combination of unusual environmental conditions: El Niņo in 1991-1992 led to a warm winter and a rainy spring in 1993. This contributed to the explosive growth of vegetation, providing food and cover for a burgeoning rodent population. The region experienced a tenfold increase in the numbers of deer mice from the year before. This population explosion, in turn, exacerbated the spread the disease.

Later that year, the virus itself was given a name: Muerto Canyon Virus, which was eventually changed to Sin Nombre virus. The disease was thusly called Hantavirus Pulmonary Syndrome. At the start of 1994, over 55 HPS cases had been documented, 32 of which were fatal.

No, definately not. The Sin Nombre virus and other New World strains of hantavirii have probably been living happily in their rodent hosts for thousands of years, long before the first immigrants even settled here. There are even references to HPS in Native American folklore -- where if you let mice live in your dwelling, they'll "take away the breath" of your children.

HPS is a "stealth" disease. Its incident rate is low enough -- and its symptoms are nondescript enough -- that it went unidentified as a specific malady for centuries. It was only identified during the 1993 outbreak because several cases occurred in the same region within a short period of time. Now that the presence of the virus can be determined with antibody tests, health officials have identified HPS patients -- both survivors and victims -- from as far back as 1959.

Yes. By being a "notifiable disease", HPS is one of over 50 diseases that is under national surveillance; whenever a case occurs, it is reported to the CDC's National Notifiable Diseases Surveillance System (NNDSS), to facilitate prevention and control of the disease.

Within the United States, cases of HPS have occured in at least thirty of the southern 48 states.

Outside of the continental United States, cases of HPS have occurred in the following countries: Argentina, Brazil, Canada, Chile, Paraguay, and Uraguay.

However, HPS carrier rodents can also be found in Bolivia, Costa Rica and Mexico, but have not yet been linked to any incidents of the disease.