Everything You Should Know About Hantavirus.
Hantaviruses are a family of viruses spread mainly by rodents and can cause varied disease syndromes in people worldwide. Infection with any hantavirus can produce hantavirus disease in people. HPS can be fatal. It has a mortality rate of 38%.
Hantavirus Pulmonary Syndrome (HPS) is a severe, sometimes fatal, respiratory disease in humans caused by infection with hantaviruses.
Anyone who comes into contact with rodents that carry hantaviruses is at risk of HPS. Rodent infestation in and around the home remains the primary risk for hantavirus exposure. Even healthy individuals are at risk for HPS infection if exposed to the virus.
The term hantavirus represents several groups of RNA-containing viruses (that are members of the virus family of Bunyaviridae) that are carried by rodents and can cause severe respiratory infections termed hantavirus pulmonary syndrome (HPS) and hemorrhagic fever with renal syndrome (HFRS).
HPS is found mainly in the Americas (Canada, U.S., Argentina, Brazil, Chile, Panama, and others) while HFRS is found mainly in Russia, China, and Korea but may be found in Scandinavia and Western Europe and occasionally in other areas. Like HPS, HFRS results from hantaviruses that are transmitted by rodent urine, rodent droppings, or saliva (rodent bite), by direct contact with the animals, or by aerosolized dust contaminated with rodent urine or feces to human skin breaks or to mucous membranes of the mouth, nose, or eyes. The vast majority of HPS and HFRS infections do not transfer from person to person.
The goal of this article is to discuss HPS; however, much of what is presented about HPS applies to HFRS — the main difference is that the predominant symptoms in the late stages of disease vary somewhat between the two diseases (lung fluid and shortness of breath in HPS and low blood pressure, fever, and kidney failure in HFRS).
HPS is a disease caused by hantavirus that results in human lungs filling with fluid (pulmonary edema) and causing death in about 38% of all infected patients.
Is Hantavirus Contagious?
Hantavirus is not contagious from person to person. The virus spreads from rodents to humans. Although outbreaks seem like there is person-to-person transfer, outbreaks are usually noted among groups of people exposed to the same infected rodent population; but those with hantavirus infections do not transfer them to other uninfected individuals. While this is the situation in North America, there are reports that in 1996, mild infections with hantaviruses were transmissible in an outbreak in Argentina. However, to date, there has been no reported person-to-person transfer of the virus in the United States. Small outbreaks are reported each year; for example, Texas had its first individual diagnosed with hantavirus in 2015.
How People Become Infected With Hantaviruses
In the United States, deer mice (along with cotton rats and rice rats in the southeastern states and the white-footed mouse in the Northeast) are reservoirs of the hantaviruses. The rodents shed the virus in their urine, droppings, and saliva. The virus is mainly transmitted to people when they breathe in air contaminated with the virus.
When fresh rodent urine, droppings, or nesting materials are stirred up, tiny droplets containing the virus get into the air. This process is known as “airborne transmission “.
There are several other ways rodents may spread hantavirus to people:
- If a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare.
- Scientists believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.
- Scientists also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.
The hantaviruses that cause human illness in the United States cannot be transmitted from one person to another. For example, you cannot get these viruses from touching or kissing a person who has HPS or from a health care worker who has treated someone with the disease.
In Chile and Argentina, rare cases of person-to-person transmission have occurred among close contacts of a person who was ill with a type of hantavirus called Andes virus.
Signs & Symptoms
Due to the small number of HPS cases, the “incubation time” is not positively known. However, on the basis of limited information, it appears that symptoms may develop between 1 and 8 weeks after exposure to fresh urine, droppings, or saliva of infected rodents.
Early symptoms include fatigue, fever and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms are universal.
There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.
Four to 10 days after the initial phase of illness, the late symptoms of HPS appear. These include coughing and shortness of breath, with the sensation of, as one survivor put it, a “…tight band around my chest and a pillow over my face” as the lungs fill with fluid.
What Causes Hantavirus Pulmonary Syndrome?
The cause of HPS is infection of the patient by hantavirus. Currently, about 14 subtypes of hantaviruses have been identified. Many subtypes have been named (for example, Sin Nombre, Black Creek hantavirus, Seoul virus, and New York hantavirus); some investigators simply lump them under the term of “New World hantaviruses.” The Sin Nombre subtype has caused the majority of current HPS disease. The virus apparently damages cells that compose blood vessel capillaries, causing them to leak fluids. This fluid leak, if it is profound in the lungs, causes the life-threatening pulmonary syndrome.
Hantaviruses live their lifecycle in rodents but apparently do no harm; the viruses multiply and shed in the rodent’s urine, feces, and saliva. A recent study in California suggested about 15% of all deer mice examined tested positive for hantavirus. Although the deer mouse has been the source of most HPS infections, many other rodents may carry a different hantavirus subtype virus (for example, the white-footed mouse, the cotton rat, and the rice rat).
What Are Risk Factors For Hantavirus Pulmonary Syndrome?
The major risk factor for HPS is an association with a rodent infestation, their saliva, urine, or feces or with dust, dirt, or surfaces contaminated with such items, either by direct contact or by aerosol. Barns, sheds, homes, or buildings easily entered by rodents (for example, deer mouse or Peromyscus maniculatus) are potential places for hantaviruses to come in contact with humans. Rural areas that have forests and fields that can support a large rodent population are areas that increase the risk of exposure to HPS. Camping and hiking in areas known to have a high rodent population and occupying areas where rodents may seek shelter increase one’s risk. Those who work in areas that may be a shelter for rodents (for example, crawl spaces, vacated buildings, construction sites) may also have increased risk of HPS. The risk is higher in people who work in areas known to have produced HPS infections.
What Is The Treatment For Hantavirus Pulmonary Syndrome?
At this time, there is no definitive treatment for HPS other than early recognition of HPS and subsequent medical support (usually consisting of symptomatic medical treatment and respiratory support or mechanical ventilation). The CDC suggests that early treatment in an intensive care unit may allow the patient to survive severe HPS. Experimentally, physicians have administered the antiviral medication ribavirin (Rebetol, Copegus), but there are no clear data currently that establish that the drug is effective against HPS; however, its use against HFRS early in the disease suggests ribavirin can decrease illness and deaths. There is no vaccine available to protect against any hantaviruses to date.