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A closer look at hantaviruses

Ly, Evelyn MPH, CPH

doi: 10.1097/01.NURSE.0000432908.39184.a8
Department: COMBATING INFECTION
Free

Hantaviruses

Evelyn Ly is infection control coordinator at Scripps Health in San Diego, Calif.

The author has disclosed that she has no financial relationships related to this article.

ACUTE ZOONOTIC viral diseases, hantaviruses infect rodents worldwide.1 First identified in 1951, hantaviruses are part of the Bunyaviridae family of viruses and can be categorized into two groups: Old World and New World hantaviruses.2 Old World hantaviruses are found in Asia and can cause hemorrhagic fever with renal syndrome. New World hantaviruses are found in the United States and Canada; the most prevalent is the sin nombre virus (SNV). SNV can progress to hantavirus pulmonary syndrome (HPS; also known as hantavirus cardiopulmonary syndrome), a severe respiratory disease in humans with 38% mortality.1,3

SNV was first recognized in the southwestern United States in 1993 when an unexplained pulmonary illness was causing young, healthy people to die of acute respiratory failure.4 The CDC began testing specimens for hantavirus after a physician noted that the illness seemed similar to hantavirus infection. This testing identified a previously unknown hantavirus that was named sin nombre, Spanish for “no name.”4

In the summer of 2012, SNV caused the outbreak of hantavirus in Yosemite National Park that infected 10 park visitors, killing three.5 According to the CDC, 587 cases of HPS have been reported in the United States since the disease was first recognized in 1993.6

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Transmission

The major reservoir of SNV is the deer mouse, but it's also been found in cotton rats, rice rats, and the white-footed mouse.7 These rodents shed the virus in their urine, droppings, and saliva.1 The virus can be transmitted to humans through a rodent's bite, but the primary route of transmission is inhalation of air contaminated with the virus.8 This occurs when rodent urine, droppings, or nesting materials are stirred up, causing airborne particles containing the virus to disperse into the air.8 Such dispersal is often the result of sweeping or cleaning cabins, sheds, attics, and outbuildings such as barns or garages infested with rodents harboring the virus. Indoor exposure in poorly ventilated homes, vehicles, or outbuildings with rodent infestation is another common route of transmission.1 Campers, hunters, or hikers can also be exposed when utilizing infested trail shelters or camping in rodent habitats. Those in professions that involve exposure to rodents, such as construction, utility work, and pest control, have an increased risk of contracting hantavirus.9

Person-to-person transmission of hantavirus is extremely rare and hasn't been reported in the United States.8 There are also no known cases of reinfection with hantavirus, but protection and duration of immunity conferred by previous infection are unknown.1,10

Rodents carrying hantavirus can be found throughout the United States; cases have been reported in all regions except Alaska and Hawaii.6 Deer mice live throughout North America, preferring to inhabit woodland areas, but can live in deserts as well. The cotton rat and rice rat can both be found in the southeastern United States, while the white-footed mouse is found throughout southern New England, mid-Atlantic and southern states, and midwestern and western states.7

Weather can also have an effect on transmission. In the 1993 outbreak, the winter was especially wet due to the weather phenomenon known as El Niño. A large crop of nuts and other rodent food spurred an increase in the number of rodents in the area, which led to an increase in the transmission of the virus to humans. This same weather pattern has been observed before other hantavirus outbreaks in the United States.11 Most cases of hantavirus occur in the spring and summer months when people are more apt to spend time outdoors.11

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Signs and symptoms

The incubation period for hantavirus is approximately 2 weeks, with a range of a few days to 6 weeks.1 Early signs and symptoms include fatigue, fever, gastrointestinal complaints, and myalgia, particularly in the large muscle groups such as the thighs, hips, back, and shoulders.3 These symptoms can be easily confused with those of influenza. However, if the patient experiences these symptoms and reports a history of potential rodent exposure, hantavirus should be considered.

If the disease progresses to HPS, approximately 4 to 10 days after the initial symptoms patients exhibit shortness of breath, a dry cough, and hypotension.12 As capillaries leak into the pulmonary bed, patients may report a sensation that one survivor described as a “tight band around my chest and a pillow over my face.”3,12 Respiratory failure often occurs as a result of noncardiogenic pulmonary edema.12 Due to hypotension, other organs such as the heart and kidneys will begin to fail as well.13

Because of its availability, ease of dissemination, and potential for high morbidity and mortality, hantavirus is classified by the CDC as a category C bioterrorist agent.14

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Diagnosing hantavirus

The early signs and symptoms of hantavirus can lead to a misdiagnosis of influenza or other viral and bacterial infections. To clinically distinguish the presence of hantavirus, a complete blood cell count with differential and platelet count should be done.15 Thrombocytopenia (<150,000/mm3) and leukocytosis with a marked bandemia are consistently seen during the prodromal phase of HPS.15,16 Other lab results suggesting early HPS include atypical lymphocytes, elevated levels of serum lactate dehydrogenase and aspartate aminotransferase, and decreased serum bicarbonate levels.15

Chest X-ray will demonstrate interstitial pulmonary edema, which will then progress to alveolar edema with severe bilateral involvement.15 Pleural effusions are also common and are often large enough to be observed in chest X-rays.16

Hantavirus can be confirmed using enzyme-linked immunosorbent assay, Western blot, or strip immunoblot techniques.1 Most patients will have immunoglobulin M present at the time of hospitalization. Hantavirus is a reportable disease, and the health department must be notified of a hantavirus diagnosis.1

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Treatment

Because there's no specific treatment or cure for hantavirus, care given to infected patients focuses primarily on respiratory management to assist them through the period of severe respiratory distress.1 Patients should receive immediate medical care, including endotracheal intubation and mechanical ventilation, as necessary, to treat respiratory failure, in an ICU so they can be closely monitored.12,17 For suspected cases of hantavirus in rural areas, rapid transfer to a tertiary care center with an ICU is important.18

During initial phases of the disease, antipyretics and analgesia are administered as needed. Patients should receive appropriate, broad-spectrum antibiotic therapy to cover for the differential diagnoses of pneumonia or sepsis while awaiting confirmation of an HPS diagnosis.19

In the ICU, care must be taken to avoid hypoxemia as well as overhydration that might lead to exacerbation of pulmonary edema.1 Fluids must be administered carefully due to the capillary leak syndrome.12 Vasopressors can also be given early under careful monitoring to prevent shock.1 No isolation precautions or quarantine are necessary while a patient is receiving care.1

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Prevention

Vaccine research is currently underway. Although countries such as China and Korea are using an inactivated vaccine locally, no approved vaccines or prophylactic agents for hantavirus currently exist in the United States or Canada.20 The most effective way to combat hantavirus infection is prevention.17

Effective preventive measures focus on minimizing exposure to rodents and their excrement as much as possible. This includes denying them access to houses and other buildings by sealing structural holes or gaps, preventing infestation by placing traps in and around buildings, and storing food in rodent-proof containers.1 When cleaning or disinfecting rodent-contaminated areas, wear rubber or plastic gloves and spray urine or droppings with a household disinfectant solution or a 1:10 diluted bleach solution, prepared by mixing 1.5 cups of household bleach with 1 gallon of water. Let it soak for 5 minutes to prevent it from aerosolizing during its removal.20 Use a paper towel to wipe up the urine or droppings and place the paper towel in the garbage. Never sweep or vacuum rodent-infested areas; use a wet mop or sponge moistened with disinfectant instead to clean the area. Wash gloved hands with soap and water before taking off the gloves, then wash hands in soap and warm water after taking off the gloves.1

When disposing of a dead rodent, wear rubber or plastic gloves. The dead rodent and its surrounding area should be sprayed with 1:10 diluted bleach and allowed to soak for 5 minutes. The dead rodent must then be placed in a tightly sealed plastic bag and that bag must be placed within another plastic bag, sealed tightly, and disposed of in a covered trashcan that's regularly emptied. Wash hands with soap and water before and after removing gloves.21,22

People disposing of and cleaning rodent-infested areas should wear respirators. These respirators should be either a half-face, tight-seal, negative-pressure respirator or a positive pressure powered air-purifying respirator equipped with N-100 or P-100 filters.21

When educating patients, emphasize the need to exclude rodents from their homes and outer buildings and outline the proper precautions and methods for disposing of dead rodents and rodent excrement to prevent hantavirus infections. Pamphlets and brochures with this information are available at www.cdc.gov/hantavirus, and patients can also call the CDC hantavirus hotline at (877) 232-3322 for more information.

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REFERENCES

1. Mackenzie JS. Hantaviral Diseases. In: Heymann DL, ed. Control of Communicable Diseases Manual. Washington, DC: American Public Health Association; 2008:269–274.
2. Centers for Disease Control and Prevention. Hantavirus: technical/clinical information. 2012. http://www.cdc.gov/hantavirus/technical/index.html.
3. Centers for Disease Control and Prevention. Hantavirus: signs and symptoms of hantavirus pulmonary syndrome (HPS). 2012. http://www.cdc.gov/hantavirus/hps/symptoms.html.
4. Centers for Disease Control and Prevention. Hantavirus: tracking a mystery disease: the detailed story of hantavirus pulmonary syndrome (HPS). 2012. http://www.cdc.gov/hantavirus/hps/history.html.
5. Centers for Disease Control and Prevention. Hantavirus: outbreak of hantavirus infection in Yosemite National Park. http://www.cdc.gov/hantavirus/outbreaks/yosemite-national-park-2012.html.
6. Centers for Disease Control and Prevention. Hantavirus: reported cases of HPS. 2012. http://www.cdc.gov/hantavirus/surveillance.
7. Centers for Disease Control and Prevention. Hantavirus: rodents in the United States that carry hantavirus. 2012. http://www.cdc.gov/hantavirus/rodents/index.html.
8. Centers for Disease Control and Prevention. Hantavirus: how people get hantavirus pulmonary syndrome (HPS). 2012. http://www.cdc.gov/hantavirus/hps/transmission.html.
10. Centers for Disease Control and Prevention. Hantavirus: technical FAQ. 2012. http://www.cdc.gov/hantavirus/technical/hps/faq.html.
11. Cooke C. Hantavirus outbreaks linked to weather patterns; scientists predict El Nino will trigger disease. SF Gate. 2002. http://www.sfgate.com/news/article/Hantavirus-outbreaks-linked-to-weather-patterns-2711569.php.
12. Hjelle B. Hantavirus cardiopulmonary syndrome. UpToDate. 2013. http://www.uptodate.com.
14. Centers for Disease Control and Prevention. Emergency preparedness and response: bioterrorism agents/diseases:by category. 2013. http://www.bt.cdc.gov/agent/agentlist-category.asp.
15. Utah Department of Health, Bureau of Epidemiology. Hantavirus is back! 1998. http://health.utah.gov/epi/newsletter/archives/jul98/Default.htm#Hantavirus.
17. Centers for Disease Control and Prevention. Hantavirus: diagnosing and treating hantavirus pulmonary syndrome (HPS). 2012. http://www.cdc.gov/hantavirus/hps/diagnosis.html.
18. Medscape. Hantavirus cardiopulmonary syndrome treatment and management: prehospital care. 2013. http://emedicine.medscape.com/article/788980-treatment.
19. Centers for Disease Control and Prevention. Hantavirus: treatment. 2012. http://www.cdc.gov/hantavirus/technical/hps/treatment.html.
20. Maes P, Clement J, Van Ranst M. Recent approaches in hantavirus vaccine development. Expert Rev Vaccines. 2009;8(1):67–76.
21. Mills JN, Corneli A, Young JC, Garrison LE, Khan AS, Ksiazek TG. Hantavirus pulmonary syndrome—United States: updated recommendations for risk reduction. MMWR Recomm Rep. 2002;51(RR-9):1–12.
22. Massachusetts Department of Public Health. Public health fact sheet: hantavirus pulmonary syndrome. 2013. http://www.mass.gov/eohhs/docs/dph/cdc/factsheets/hantavirus.pdf.
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