Epidemiological Analysis of Hantavirus Pulmonary Syndrome

I. Background Information

Hantavirus Pulmonary Syndrome is an infectious disease that is caused by a Hantavirus known as Sin Nombre and is carried by rodents. Unlike the usual viruses, this particular one does not rely on an arthropod as a vector, but rather uses rodents that include mice and rats (Utah Department of Health Bureau of Epidemiology, 2012). As an infectious disease, HPS does not pass between humans but is rather contracted by coming into contact with air that is contaminated with the rodents urine, droppings or nesting materials. This paper analyzes HPS, examining how the disease is spread, diagnosed and treated, while also establishing its preventive measures by considering who is at risk and why. In addition, the paper will discuss the factors around this disease, including the agent, vector, host and favorable environment.

According to Utah Department of Health Bureau of Epidemiology (1998), Hantavirus Pulmonary Syndrome is an infectious disease that was first cited in the US in May 1993, when a relatively healthy young Navajo man fell critically ill and died upon arriving at the Emergency Room. The symptoms were mainly flu like, muscle ache, chills and fever, and then he developed acute shortness of breath. This caused his lugs to fail and eventually he succumbed to the disease. Since that day, scientists have been involved in vigorous research and analysis on Hantavirus Pulmonary Syndrome, although it has been in the existence for so many decades before that episode at the Four Corners (Department of Health Bureau of Epidemiology, 2012). As a disease, HPS is rapidly progressing, with the quick diagnosis being impeded by its flu like symptoms. Meanwhile, the disease has been successfully managed in a number of cases, the threat is quite high if the diagnosis is significantly delayed as the respiratory distress damages the lungs and the heart.

II. Occurrence

The first reported case of HPS was that of a young man in the Four Corners area of Arizona, Colorado, Utah and New Mexico (Department of Health Bureau of Epidemiology, 2012). The virus went on to infect more people from the Four Corners area before it was reported in other parts of the world too.

People who are mostly infected are campers and hikers who come into contact with the rodents in their campsites and cabins. Furthermore, people who generally live in the rural areas and are likely to have encountered rodents in their farms, fields, barns and other outbuildings are more likely to contract the disease. A further risk is associated with the construction, utility and pest control workers, who are likely to work in closed and unused spaces in which rodents are likely to exist in significant numbers.

With regards to the timing, the rodent populations have been found to increase significantly during spring and fall. Simultaneously, the reports of HPS also increase during these seasons, implying that the large numbers of rodents contribute towards more exposure to Hantaviruses and more specifically the Sin Nombre Hantavirus that is associated with HPS.

III. Factors

HPS is caused by Hantaviruses, and more specifically, the Sin Nombre Hantavirus that is more common in the US. A Hantavirus is a unique member of the largest animal virus family that is known as Bunyavuridae (Williams & Barker, 2001).These are single stranded, enveloped and usually negative-sense RNA viruses with three genomic segments. They also have larger nucleocapsids and an unusual grid like a pattern on their surfaces. It can, thus, be said that the causative agent of HPS is a unique virus from the Bunyaviridae family (Department of Health Bureau of Epidemiology, 2012).

With regards to the vector, HPS is contracted by breathing air that is contaminated with the droppings, urine, nesting materials and saliva of the carrier rodents (Department of Health Bureau of Epidemiology, 2012). This implies that it is airborne in that it is contracted through the air. However, research also indicates that one can contract the virus by touching contaminated material and then touching their mouth or nose without cleaning their hands. Moreover, eating contaminated food makes one more likely to contract the disease. It can, thus, be said that the disease vector is the air, but this does not rule out the fact that one can contract it if they eat food that has been exposed to the rodents urine, droppings, saliva or nesting materials.

HPS is caused by the Sin Nombre Hantavirus, which is found in rodents. This makes the rodents their natural host. Once a rodent is infected by this virus, they may experience a minor adjustment period of up to ten days before being persistently asymptomatic for the rest of their lives. This means that they do not fall sick but rather accept the virus as a part of their system. There are a wide variety of rodents that carry Hantaviruses, but the Sin Nombre is specifically carried by the deer mice. Other known carriers or natural hosts include the white footed mice, cotton rat and rice rat, but each carries a specific constraint of Hantaviruses, depending on their regional habitats. The deer mice are specifically more common in the central and western parts of the US and Canada; thus, they are responsible for most of the Hantavirus infections within the country.

Rodents generally live in areas that are favorable to their existence in terms of availability of food and water. In terms of the environment, it can be stated that HPS is common in areas that have forests, farms, fields, barns, outbuildings, and other unused spaces that are closed. These may include basements, pool houses, cabins and other similar structures. All these are common in the rural areas, implying that HPS is more likely to affect the rural populations.

IV. Threat Assessment

HPS is a potentially fatal disease that may lead to death if not caught early enough. This implies that it is a serious life threatening disease that requires accurate threat assessment. With regards to its level of threat, the fatalities have been reported to be as high as 50%. The major cause is, however, the rodent infestation, and this is something that can be controlled. While those in rural areas are at a higher risk, hikers and campers as well as construction, utility and pest control workers also need to take precautionary measures such as protective gear and avoiding spaces that have been unused and closed up for long periods of time.

One likely scenario for an outbreak would be if the numbers of rodents suddenly shoot up in the rural areas as it did between May 1992 and May 1993. The rodent population had gone up by about 1000%, thus increasing the contact between people and the mice (Centers for Disease Control and Prevention, n.d.). If the rodents populations are not controlled, then the resident populations are likely to experience an outbreak of HPS, and with the high fatality rating, this may be a catastrophic eventuality.

V. Medical Treatment

Like many other viruses, the Sin Nombre Hantavirus remains a substantial challenge to the scientific community. An effective treatment is yet to be discovered for this disease, but recovery has been observed in patients, who are given supportive treatment for the symptoms (Centers for Disease Control and Prevention, n.d.). This means that the body can fully recover from an infection on its own, provided the patient survives the severe symptoms.

The supportive treatment is often provided for the breathing difficulties by intubation and oxygen therapy to avoid lung failure. Usually, when a patient reports to the hospital with HPS, they are immediately admitted to the ICU for assisted breathing until the infection clears out. In some cases, there may be complications, such as lung or even heart failure, and these are the common causes of the deaths related to this disease.

VI. Preventive Measures

Considering that the disease is associated with exposure to rodents urine, droppings, saliva and nesting materials, the most effective preventive measure would be to eliminate any rodents from ones home or place of work. This has in some cases, however, been proven impossible, for example, in the fields and farms, forests, mountain cabins and other unoccupied buildings like barns and tool sheds. This means that there should be something more that people, especially in the rural areas, can do to minimize their risk of contracting this disease.

First, the home should be kept as rodent free as possible by setting traps, blocking any holes in the walls or on the floor and ensuring that the house is kept generally clean and free from food crumbs. This will ensure that the rodents are kept away from the living quarters, thus minimizing the eventuality of an encounter with the carriers of this deadly disease.

When one has to go camping, they should also ensure that they keep their camps rodent free, by camping in areas that are frequented as opposed to isolated cabins deep in the woods. Avoiding rodents keeps the chances of coming into contact with their droppings, urine, saliva or nesting materials at a minimal even when outdoors. Furthermore, camping and hiking in known rodent breeding areas should be avoided at all costs.

For those working in construction, utilities or pest control, buildings that have been closed off for a long period of time should be avoided or rather entered, while wearing a protective gear. These include barns and other buildings which may be breeding grounds for rodents if closed off for long periods of time (Heymann, 2008).

Another common way of contracting HPS is during cleaning, both indoors and outbuildings. It is, thus, extremely important for people in the rural areas to avoid cleaning out their homes while unprotected. They should wear gas masks and hand gloves in order to avoid breathing in the contaminated air. In addition, with regards to the contraction of the infection through eating contaminated foods, people living in areas with high rodent populations should ensure that their foods are kept in sealed containers and that the easy to reach foods and fruits are thoroughly cleaned before they are eaten or cooked. This will ensure that they are protected from infection by ingestion.

Lastly, the infection by touching contamination and transferring it to ones nose or mouth can be prevented by the avoidance of touching oneself during house cleaning exercises. If one must touch themselves while they clean their house, he or she should do so after cleaning their hands even if they had been wearing gloves.

VII. Conclusion

Hantavirus Pulmonary Syndrome is a disease that is caused by the Sin Nombre Hantavirus and affects ones ability to breathe properly. While the disease starts with flu like symptoms, the progression indicates acute respiratory distress syndrome and eventual lung or heart failure. This means that it is a dangerous disease and has registered fatalities of up to 50%. In the US, this disease is common in the rural areas, especially in the western and central parts of the country, where deer mice can be found. The disease is most common in spring and fall, when the rodent populations spike significantly, and there is no specific antiviral therapy available for its treatment. The supportive treatment is, however, available to help patients in coping with the severe acute respiratory distress syndrome that characterizes the infection. There are a number of preventive measures that individuals in the rural areas can take to minimize their risks of exposure, one of which is simply eliminating rodents from their living quarters.

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