Infectious Disease and Microbiology – Hantavirus Group

Overview

Hantaviruses are enveloped, segmented, negative-sense single-stranded RNA viruses that cause two major human disease patterns: hantavirus pulmonary syndrome (HPS), also called hantavirus cardiopulmonary syndrome, and hemorrhagic fever with renal syndrome (HFRS).

The clinical syndrome depends largely on the viral species and geographic region. In the Americas, hantaviruses such as Sin Nombre virus are particularly associated with severe pulmonary disease, whereas Eurasian hantaviruses such as Hantaan, Seoul, Puumala, and Dobrava-Belgrade viruses are primarily associated with HFRS.

Classification

Hantaviruses historically belonged to the family Bunyaviridae but are now classified within the family Hantaviridae.

Multiple hantavirus species are capable of causing human disease.

Microbiologic Characteristics

Hantaviruses are:

• Negative-sense single-stranded RNA viruses

• Enveloped

• Characterized by helical nucleocapsid symmetry

• Equipped with a three-segmented RNA genome

The three RNA segments are conventionally designated:

L = Large

M = Medium

S = Small

Epidemiology

Human hantavirus infections are relatively rare, but they can produce severe and potentially fatal disease.

The viruses are maintained primarily in rodent reservoirs, with different hantavirus species associated with particular rodent hosts and geographic regions.

Transmission

Humans usually acquire infection through exposure to infected rodent excreta.

Transmission commonly occurs through:

Inhalation of aerosolized virus from rodent urine, feces, or saliva

Exposure can occur while:

• Cleaning rodent-infested buildings

• Entering poorly ventilated structures containing rodents

• Handling contaminated materials

• Working or camping in rodent-infested environments

Major Clinical Syndromes

Hantavirus infection produces two major syndromes:

Hantavirus Pulmonary Syndrome (HPS)

Predominantly associated with hantaviruses of the Americas.

Hemorrhagic Fever With Renal Syndrome (HFRS)

Predominantly associated with hantaviruses of Europe and Asia.

Hantavirus Pulmonary Syndrome

Sin Nombre Virus

Sin Nombre virus is the classic cause of hantavirus pulmonary syndrome in the United States.

It became particularly recognized after an outbreak in the southwestern United States.

The historical term Muerto Canyon virus was initially used for the virus subsequently named Sin Nombre virus.

Clinical Course of HPS

The illness often begins with nonspecific symptoms such as:

• Fever

• Severe myalgia

• Headache

• Malaise

• Gastrointestinal symptoms

This initial febrile phase may be followed by rapidly progressive cardiopulmonary disease.

Pulmonary Phase

The major complication is:

Rapidly progressive pulmonary edema and respiratory failure

Patients may develop:

• Cough

• Dyspnea

• Hypoxemia

• Bilateral pulmonary infiltrates

• Noncardiogenic pulmonary edema

• Respiratory failure

Severe disease can progress rapidly to shock.

Cardiovascular Involvement

HPS can involve not only the lungs but also the cardiovascular system.

Severe cases may develop:

• Hypotension

• Myocardial dysfunction

• Shock

For this reason, the term hantavirus cardiopulmonary syndrome is also used.

High-Yield HPS Pattern

Rodent exposure in the Americas

• ●

Fever and severe myalgia

• ●

Rapidly progressive pulmonary edema

• ●

Hypoxemic respiratory failure

→ Think hantavirus pulmonary syndrome

Hemorrhagic Fever With Renal Syndrome

Overview

HFRS is primarily associated with hantaviruses circulating in Europe and Asia.

Important viruses include:

• Hantaan virus

• Seoul virus

• Puumala virus

• Dobrava-Belgrade virus

Severity varies substantially according to the infecting virus.

Clinical Manifestations of HFRS

Patients may develop:

• Fever

• Headache

• Myalgia

• Thrombocytopenia

• Hemorrhagic manifestations

• Hypotension

• Acute kidney injury

• Proteinuria or hematuria

Renal involvement is a defining feature.

Hantaan Virus

Hantaan virus is classically associated with more severe hemorrhagic fever with renal syndrome, particularly in East Asia.

Disease can include substantial vascular leakage, hemorrhage, hypotension, and renal dysfunction.

Puumala Virus

Puumala virus generally causes a milder form of HFRS, often referred to as:

Nephropathia epidemica

Renal abnormalities remain prominent, but the overall disease is typically less severe than classic Hantaan-virus-associated HFRS.

Seoul Virus

Seoul virus can cause HFRS and is notable for its association with rats.

Because its rodent reservoir has a broad geographic distribution, Seoul virus infections are not restricted to a single region.

Prospect Hill Virus

The source includes Prospect Hill virus among hantaviruses.

However, it is important to distinguish hantaviruses known to cause established human disease from those primarily identified in rodent reservoirs. Prospect Hill virus has not been a major established cause of classic human HFRS.

Diagnosis

The source lists:

• Cell culture

• Serology

In clinical practice, hantavirus diagnosis is more commonly based on:

• Serologic testing for hantavirus-specific antibodies

• RT-PCR or other molecular methods in appropriate settings

Routine viral culture is generally not the main diagnostic approach.

Treatment

Management is primarily supportive and depends on the syndrome.

For HPS, treatment may require:

• Intensive monitoring

• Oxygen supplementation

• Mechanical ventilation

• Hemodynamic support

• Management of shock

Severe cardiopulmonary disease may require advanced critical-care support.

Ribavirin

The source describes an intravenous ribavirin regimen that had been investigated, particularly for HFRS.

However, the source also notes disappointing early results in the United States.

Ribavirin should therefore not be interpreted as a universally effective treatment for all hantavirus syndromes, particularly HPS, where management is predominantly intensive supportive care.

Prevention

Prevention focuses primarily on avoiding exposure to infected rodents and their excreta.

Important measures include:

• Rodent control

• Preventing rodents from entering homes and workplaces

• Safe cleanup of rodent-contaminated environments

• Avoiding activities that aerosolize dried rodent urine or feces

• Appropriate protective precautions during high-risk exposure

Isolation – Important Correction

The source recommends:

“Strict isolation during the entire illness.”

This is not a general requirement for all hantavirus infections because most hantaviruses are transmitted from rodents to humans rather than from person to person.

A notable exception is Andes virus, for which person-to-person transmission has been documented.

Therefore, infection-control precautions should depend on the specific hantavirus and epidemiologic circumstances.

HPS vs. HFRS

Hantavirus Pulmonary Syndrome

→ Primarily Americas

→ Sin Nombre virus is classic in the United States

→ Pulmonary capillary leak

→ Pulmonary edema

→ Respiratory failure

→ Shock may occur

Hemorrhagic Fever With Renal Syndrome

→ Primarily Europe and Asia

→ Hantaan, Seoul, Puumala, Dobrava-Belgrade viruses

→ Hemorrhagic manifestations

→ Thrombocytopenia

→ Acute kidney injury

High-Yield Clinical Pattern – HPS

Southwestern United States

• ●

Rodent exposure

• ●

Acute febrile prodrome

• ●

Rapid pulmonary edema and respiratory failure

→ Think Sin Nombre virus causing hantavirus pulmonary syndrome

High-Yield Clinical Pattern – HFRS

Rodent exposure in Europe or Asia

• ●

Fever

• ●

Thrombocytopenia/hemorrhagic manifestations

• ●

Acute renal failure

→ Think hantavirus-associated HFRS

Exam Essentials

Virus group: Hantaviruses

Family: Hantaviridae

Genome: Negative-sense single-stranded RNA

Genome structure: Three segments – L, M, S

Envelope: Present

Reservoir: Rodents

Typical transmission: Inhalation of aerosolized rodent excreta

Major syndromes: HPS and HFRS

Classic U.S. virus: Sin Nombre virus

Sin Nombre syndrome: Hantavirus pulmonary syndrome

Major HPS complication: Pulmonary edema and respiratory failure

Hantaan virus: Severe HFRS

Puumala virus: Generally milder HFRS/nephropathia epidemica

Seoul virus: HFRS; associated with rats

HFRS hallmark: Acute kidney injury ± hemorrhage

Diagnosis: Primarily serology; molecular testing can also be used

Treatment: Mainly supportive

Ribavirin: Historically investigated, particularly for HFRS; not established as effective therapy for HPS

Prevention: Rodent exposure control

Person-to-person transmission: Generally absent; Andes virus is an important exception

Key clinical pearl: Hantaviruses are three-segmented, enveloped, negative-sense RNA viruses transmitted primarily from rodents. For examinations, separate the two classic syndromes: Sin Nombre virus in the Americas → hantavirus pulmonary syndrome with pulmonary edema and respiratory failure; Hantaan and related Eurasian viruses → hemorrhagic fever with renal syndrome characterized by acute kidney injury and possible hemorrhage.