Key Facts

  • At least 13 countries in the Americas have endemic areas.
  • Every year, there are approximately 300 cases reported in the Americas.
  • From 1993, when the virus was initially recognized, until 2016, more than 6300 cases have been registered in countries of the region where the disease is under surveillance
  • Hantavirus infections can be fatal.
  • Fatality rates may reach up to 60%.
  • There is no available treatment.
  • Early diagnostic may reduce fatality rates by half.
  • It can be prevented by reducing contact with rodents and their excrement, as well as through hygienic practices to prevent rodent infestations in the home, workplace and recreation areas.

Definition

Hantavirus (HV) is an emerging zoonotic disease transmitted by rodents such as mice and rats. It is characterized by symptoms of fever, myalgia, and gastrointestinal complaints, followed by sudden onset of respiratory distress and hypotension. The agent responsible for the disease comes from the Hantavirus genus, from the Bunyaviridae family. It takes its name from the Hantaan river in South Korea, where it was originally discovered in 1978.

The most common clinical form of the disease in the region is Hantavirus Pulmonary Syndrome (HPS) which can lead to death. Symptoms of HPS may develop up to 42 days -and in some cases up to 56 days- after exposure , making it difficult to identify the exact source of infection.

The disease was initially detected in the Region in 1993, when an epidemic led to 27 cases in the southeast area of the United States. However, retro-analysis of the disease reveals cases from as early as 1959.

Transmission

Cases of human hantavirus infection usually occur in rural areas (forests, fields, farms, etc.), where rodents hosting the virus may be found. However, transmission may also occur in urban areas. The virus is contracted through the inhalation of rodent droppings (urine and feces) and saliva. Only some types of rat and mouse can transmit the virus that causes HPS to people.

Simplified hantavirus infection cycle.

sylvatic cycle

The chance of exposure to hantaviruses is greatest when individuals work, play, or live in enclosed spaces where there is an active rodent infestation. Human infection does not appear to be limited to a particular age, race, ethnic group, or gender.

It is unknown if direct transmission can occur when larger particles come into contact with ocular, nasal, or oropharyngeal mucous membranes. However, small skin breaks and rodent bites are probably effective but uncommon routes of human infection.

Ticks, fleas, mosquitoes, and other biting arthropods do not have a role in the transmission of hantaviruses. Although cats and dogs are not known to host hantaviruses, these domestic animals may bring infected rodents into contact with humans

Symptoms

The incubation period varies from a few days to six weeks after exposure. Infected individuals may experience headaches, dizziness, chills, fever and myalgia. They may also experience gastrointestinal (GI) symptoms including nausea, vomiting, abdominal pains, and diarrhoea, followed by sudden onset of respiratory distress and hypotension.

Diagnosis and treatment

Early identification and timely medical care improves clinical outcome. Care during the initial stages of the illness should include antipyretics and analgesics as needed. In some situations, patients should receive broad-spectrum antibiotics while confirming the etiologic agent.

Given the rapid progression of HPS, clinical management should focus on the patient's haemodynamic monitoring, fluid management, and ventilation support. Severe cases should be immediately transferred to intensive care units (ICUs).

Hantavirus infections may resemble other diseases such as leptospirosis, dengue fever, chikungunya and even influenza in the early stage. Including this disease in the differential diagnosis concerning febrile syndromes may result in a timelier recognition and improved case management.

Fatality rates may significantly decrease through early recognition and decentralization of laboratories allowing for early detection and better case management.

Prevention

HPS occurrence can be prevented by reducing people’s contact with rodents and their excrement, as well as well as through hygienic practices prevent rodent infestations in the home, workplace and recreation areas. There is currently no vaccine against hantavirus in the Americas.

Preventive measures should be employed against occupational and eco-tourism related hazards. While most usual tourism activities pose little or no risk of exposing travelers to rodents or their excreta, people who engage in outdoor activities such as camping or hiking should take precautions to reduce possible exposure to potentially infectious materials. WHO recommends the implementation of integrated environmental management, with the goal of reducing rodent populations.

Measures to reduce personal risk

Rodent and infection control are the primary measures to be employed to reduce personal risk. Specific recommendations include reducing their food sources and sites where rodents can nest, both inside and outside the home; recommendations for eliminating rodents from the home and preventing them from entering; precautions to avoid hantavirus infection while cleaning areas contaminated by rodents; prophylactic measures for people with occupational exposure to wild rodents; and precautions to protect campers and hikers.

Some recommendations include:

  • Carry out rodent control campaigns to reduce rodent populations.
  • Seal any holes in the home and reduce the chances of rodents burrowing within a 30-meter radius of the home.
  • Eliminate any elements that may attract rodents around the home (including food, grain, garbage).
  • Use protective equipment to carry out agricultural and cleaning work. 

Distribution

The distribution of hantavirus solely depends on the ecology of its reservoir. Therefore, if the distribution of virus-carrying rodents is known, the emergence of human cases may be predicted. Approximately 40 variants have been identified in the continent, each associated to a specific reservoir.

Although not all countries have reported human cases, this may have been underestimated due to its resemblance to other febrile illnesses. Furthermore, field studies on rodents have shown that hantaviruses are circulating in countries where the disease is not reportable and that are in proximity to endemic territories

Cases

Every year, available data shows that approximately 300 cases are reported in the Americas. However, this disease is most likely underestimated due to limited surveillance. From 1993 to 2016, more than 6300 cases were registered in countries of the region where the disease is under surveillance. These include various types of hantavirus of diverse virulence and clinical specifications.

It is worth noting that whilst hantaviruses may circulate throughout the region, this virus is not a reportable disease in all PAHO member countries. This poses a challenge when assessing the burden and extent of this zoonosis and hinders the development of potential interventions to reduce its incidence.

Number of hantavirus cases reported in the Americas until 2016

 — Number of cases as of December 31st, 2016
North America 800
Canada 109
United States 691
   
Central America 269
Costa Rica 3
Panama 266
   
South America 5,243
Argentina 1,350
Bolivia 300
Brazil 2,032*
Chile 1,028
Ecuador 73
French Guiana 3
Paraguay 319
Peru 6
Uruguay 169
   
Total 6,355

* Until September 2017

Recommended HPS Case definition 

Clinical case definition

  • A febrile illness (T > 38.3 °C [101 °F] oral) requiring supplemental oxygen, PLUS
  • Bilateral diffuse infiltrates (may resemble adult respiratory distress syndrome [ARDS]), PLUS
  • Develops within 72 hours of hospitalization in a previously healthy person, OR
  • Unexplained illness resulting in death plus an autopsy examination demonstrating noncardiogenic pulmonary edema without an identifiable specific cause of death

Laboratory criteria for diagnosis

  • Presence of hantavirus-specific IgM antibodies or a 4-fold or greater increase in IgG antibody titers or hantavirus-specific IgG seroconversion.
  • Positive reverse transcriptase-polymerase chain reaction (RT-PCR) results for hantavirus RNA, OR
  • Positive immunohistochemical results for hantavirus antigens.

Case classification

Suspected: Presentation compatible with the clinical case definition.

Confirmed: A suspected case that is laboratory confirmed.

Diagnosis

  • Virological diagnosis:RT-PCR
  • Serological diagnosis:IgM determination or IgG determination using ELISA and tissue immunohistochemistry.