What Is Hantavirus Pulmonary Syndrome?

Viruses are some of the smallest particles known to exist, but unlike bacteria, fungi, plants, and animals, they are not considered living beings. These tiny organisms have the potential to spread deadly diseases. Hantavirus is a member of the virus that causes Hantavirus Pulmonary Syndrome (HPS).

A viral infection called HPS infects mice and rats and causes the disease to develop. If you come into contact with an infected rodent, your heart, lungs, and other organs may suffer harm. It advances rapidly and can be fatal. HPS is also termed hantavirus cardiopulmonary syndrome (HCPS).

This article will provide all the necessary details to understand this condition and take appropriate precautions because symptoms could rapidly worsen and pose a life-threatening hazard.

Overview

Hantavirus, often known as Hantavirus pulmonary syndrome (HPS), is a pulmonary illness defined by pulmonary oedema, hypoxia, and hypotension. Unspecified flu or hemorrhagic fever and renal syndrome (HFRS) may precede it. It usually arises by exposure to mouse urine or faeces, and within 1 to 3 weeks, the symptoms begin. The Southwest of the United States and South America have the highest rates of hantavirus. The most common form of Hantavirus sickness in the US is cardiopulmonary syndrome. Hemorrhagic fever with renal insufficiency syndrome is more prevalent in Europe and Asia.

According to the CDC, as of the end of 2021, 850 cases of HPS and non-pulmonary Hantavirus infection had been reported in the US since monitoring began in 1993. Although only a few per cent of confirmed cases have occurred in the UK, the first reported case was in 2012 when the virus originated from wild rats. According to some estimates, 50% of infections result from exposure in or near the home, 10% from working environments, and 5% from leisure activities. The remaining interaction has a variety of unknown origins. About 70% of all instances reported in the US come from seven states represented in the pie diagram showing % of prevalence.¹

 Created by: Deepika Rana

Causes of Hantavirus pulmonary syndrome

The most deadly member of the Hantavirus family, the Sin Nombre virus (SNV), is the primary cause of HPS. Within the Bunyaviridae family, the genus Hantavirus contains hantaviruses. Deer mice are reservoirs for hantaviruses in the United States, cotton and rice rats in the Southeast and white-footed mice in the Northeast. Hantaviruses linked to the murinae family typically cause HFRS, while those related to the sigmodontinae family typically cause HPS. 

The rats release the virus in their saliva, faeces, and urine. People typically contract the virus:

• By inhaling air contaminated with the virus, a process known as airborne transmission.
• By rubbing their nose or mouth and having contact with anything infected with rodent urine, faeces, or saliva.
• By eating food contaminated with rodent urine, faeces, or saliva.

There is no human-to-human transmission of the hantaviruses that infect humans in the United States and cause sickness. Rarely, close contacts of someone who had the Andes virus, a kind of Hantavirus, have been exposed to one another in Chile and Argentina.²

Signs and symptoms of Hantavirus pulmonary syndrome

Early signs of HPS

• Fever with chills
• Fatigue 
• Muscle aches (myalgias)
• Cough
• Stomachache
• Headache
• Diarrhoea
• General discomfort (malaise)
• Shortness of breath
• Tachycardia
• Tachypnea
• Disorientation
• Arthralgia
• Chest and back pain
• Sweating
• Nausea and vomiting

As HPS progresses, it can lead to:

• Pulmonary oedema
• Difficulty in breathing
• Hypoxemia
• Shock
• Respiratory distress
• Hypotension^3,4

Management and treatment

Since there is no specific therapy for HFRS or HPS, care is primarily supportive. Patients with a severe disease course need hospitalisation in the intensive care unit for close monitoring to keep euvolemia and electrolyte balance.

Created by: Deepika Rana

Supportive therapy includes:

• Supplementing oxygen
• Mechanical ventilation
• Fluid replacement
• Antiviral therapy: Ribavirin was examined for effectiveness in HFRS patients in China and discovered to have a statistically significant positive effect when used early during the illness.
• Immunotherapy: The administration of human-neutralising antibodies during the acute stage of HPS is beneficial in treating hantaviral infections.
• Vaccines: There isn't an HPS vaccine that has received FDA approval in the U.S. A killed-virus vaccine, akin to methods used in China and Korea, is not currently being developed for several reasons, including the risks involved with the large-scale production of viruses under high containment and unanswered concerns regarding the efficacy of killed-virus vaccines.^5,6

Patients with cardiopulmonary failure due to HPS who are not responding to standard intensive care therapy techniques may receive this support via extracorporeal membrane oxygenation (ECMO), which can improve their prognosis.⁷

Diagnosis

Clinical, epidemiological, and laboratory data are analysed to establish a diagnosis of Hantavirus infections.^8,9 

Essential components include:

Risk factors

Occupational hazards 

A higher risk of exposure to rats infected with the Hantavirus can result from specific jobs and activities. These people include those engaged in forestry/outdoor recreation (campers, hikers, and people spending time in remote or wilderness areas where rodents may be present), oil drilling, and the cleaning sector (e.g., janitors and house cleaners). Those employed in construction (electricians, carpenters, roofers), agriculture (farmers, ranchers, and temporary labourers), janitors, and house cleaners clean the area.¹⁰

Residential factors

Living in rural or semi-rural settings with a larger rodent population. More information is required to determine if manufactured homes and cars enhance the danger of rat infestation and hantavirus exposure due to their construction.¹⁰

Climate and environmental trends

Environmental risk factors might be endemic or epidemic. The static habitat structure of a region is related to endemic risk factors. Epidemic risk factors are dynamic phenomena linked to extensive environmental changes with short duration. They have a connection to the static habitat structure of a geographic area. With early detection of these endemic and epidemic risk factors, health agencies can predict where and when the next HPS outbreak will likely occur, allowing them to concentrate on preventative measures.¹⁰

Complications

Acute tubular necrosis may cause renal failure. Cardiorespiratory collapse, shock, or chronic non-cardiogenic pulmonary oedema are possible outcomes of severe capillary pulmonary leakage.²

FAQs

How can I prevent hantavirus pulmonary syndrome?

• Minimise human-rodent interaction.
• Keep pests under control and get mice out of the house.
• Use gloves and air filtration to handle dead rodents with care.
• Stop the spread of the infection by ventilating homes and enabling natural light to enter the region to neutralise the virus with UV radiation. 
• Restrict the amount of food available to rodents.
• Do not use your bare hands to collect dust or handle rodent droppings.¹

How common is hantavirus pulmonary syndrome?

Hantavirus pulmonary syndrome is a rare condition. Since the number of nations affected varies yearly, the overall number of Hantavirus case reports is generally rising. Changes in rat populations, which lead to human disease outbreaks, are correlated with climatic, ecological, and environmental changes.¹

When should I see a doctor?

Seek immediate medical attention if you suspect HPS or encounter worsening symptoms or problems, have come into contact with rats or their excrement directly and have been in a location where the Hantavirus is known to be present. The first step to better outcomes is early diagnosis and treatment.

Summary

HPS poses a significant risk to public health in endemic areas due to its irregularity and unpredictability, high case fatality rate, and absence of immunisations. Additional long-term research of various hantavirus species is required to accurately predict how changing environmental conditions will impact host prevalence and illness incidence in humans. Early detection, immediate medical assistance and preventative measures are crucial to reducing the risk of HPS.