Overview

Hantavirus describes a group of viruses responsible for causing serious, and sometimes fatal, lung-related and flu-like symptoms. Hantavirus is a mostly zoonotic disease, meaning that humans become infected with the disease after coming into contact with animals that are carrying the disease. The main animals responsible for the spread of hantavirus are rodents, and each strain of hantavirus is typically associated with a different rodent species.

What is hantavirus?

Hantavirus is a group of viruses that cause viral infections. It is mainly spread through human contact with the bodily fluids of infected rodents, but can also be spread by bats and shrews.¹ Currently, there are no known cures for hantavirus. Treatment is supportive and based on the symptoms presented by the patient. Hantavirus is responsible for three types of illness: 

• Hantavirus pulmonary syndrome 
• Haemorrhagic fever with renal syndrome 
• Nephropathia epidemica 

Hantavirus pulmonary syndrome 

Hantavirus Pulmonary Syndrome (HPS) is a type of hantavirus illness most commonly seen in the Americas. In North America, the most common virus causing HPS is the Sin Nombre virus, whereas in South America, the most common virus is the Andes virus.¹ The Andes virus is unique as it is the only hantavirus that can be passed from human to human. 

The initial symptoms of HPS begin 1-8 weeks after the body is first exposed to the virus and include:

• Tiredness 
• Fever 
• Muscle aches 
• Headache 
• Chills 
• Dizziness 
• Gastrointestinal issues: nausea, vomiting, diarrhoea 

A week after the initial symptoms begin, more severe symptoms may occur, including:

• Cough
• Shortness of breath 
• Chest tightness 

HPS is the most fatal form of hantavirus, with up to 40% of people who contract the virus sadly passing away. 

Haemorrhagic fever with renal syndrome 

Haemorrhagic Fever with Renal Syndrome (HFRS) is the hantavirus syndrome that mostly affects Europe and Asia. There are four common strains of HFRS: Dobrava, Puumula, Seoul and Hantaan.^1,2 The most common Hantavirus strains in Europe are Dobrava and Puumula. China is the country with the highest occurrence of hantavirus in the world, and the most common strains found there are the Seoul and Hantaan viruses.²

Similar to HFS, there is a delay between the time of contracting HFRS and the onset of symptoms. In HFRS, symptoms begin to develop 1-2 weeks after contact with an infected animal and include: 

• Severe headaches
• Back pain
• Stomach pain 
• Fever 
• Chills
• Nausea 
• Blurred visions 

Later and severe symptoms of HFRS include: 

• Low blood pressure
• Lack of blood flow
• Internal bleeding 
• Kidney failure

Fatality and severity of symptoms are dependent on the virus strain that you are infected with. The fatality of HFRS is much lower than that of HPS, with a general fatality rate between 1% and 15%.² The Hantaan and Dobrava viral strains cause the most severe reactions and have fatality rates of between 5-15%, and the Seoul and Saaremaa viruses have fatality rates below 1%.²

Nephropathia epidemica 

Nephropathia Epidemica (NE) is a milder form of HFRS and is caused by the Puumala virus. It is predominantly seen in Scandinavian countries but exists throughout Europe.² 

Transmission pathways

Rodents, bats and shrews are all responsible for spreading hantavirus. The virus is found in the urine, faeces and saliva of infected animals and can be picked up by humans in the following ways: 

• Inhaling the virus
• Eating food that has been contaminated 
• Rarely, being bitten or scratched by a rodent infected with Hantavirus 
• Rarely, human-to-human transmission

Despite being a predominantly zoonotic disease, there is one form of hantavirus that can be spread from human to human. It is the Andes virus and is found in South America; however, such cases are extremely rare. 

Rodent species associated with hantavirus

Bank vole 

The bank vole is the only known carrier of the Puumala hantavirus, the predominant hantavirus found in Europe.^2,3 The bank vole is native to the majority of Europe and parts of Central Asia.³ 

Characteristics of the bank vole

• Habitat: Bank voles can be found near riverbanks, forests and swamps, In urban areas, they can be found in hedges and gardens
• Size: Bank voles are the smallest of the vole family, growing up to 12 cm in length, with a tail that is approximately half the length of their body.
• Population and reproduction: Bank voles are very common in the areas where they are found. They have short gestation periods of 17-24 days and give birth to up to 10 pups. On average, female bank voles have 4 litters a year. The lifespan of a bank vole is 18 months
• Behaviour: Bank voles can be seen during the day and night, but are most likely to be seen shortly before sunrise and just after sunset

Brown rat

The brown rat, also known as the common or Norway rat, is one of two main carriers of the Seoul hantavirus and can be found all over the world.³ The brown rat is believed to be native to Asia but has spread throughout the world via ships and migration to Europe through Russia.⁴

Characteristics of the brown rat 

• Habitat: Brown rats can be found anywhere where humans live and live in any climate except extreme climates such as deserts or polar regions. In urban areas, they can be found in sewage systems, basements and abandoned buildings.⁴ They are also found in forests and fields
• Size: Including the tail, the average brown rat is over 40 cm long, and their tail is slightly shorter than the length of their body
• Population and reproduction: Brown rats have gestation periods of 21-24 days and give birth to 7-8 pups.⁴ A female can have up to 5 litters a year, and the lifespan of a rat is around 1 year⁴
• Behaviour: Brown rats are nocturnal and are commonly seen at sunset or during the night⁴

Black rat

The black rat, or ship rat, is the second most common spreader of the Seoul hantavirus, after the brown rat.³ It received the name ship rat due to its common presence on ships and near seaports. Black rats are thought to be native to India, but, similarly to brown rats, ship transportation brought them to countries all around the world. 

Characteristics of the black rat  

• Habitat: Black rats are uncommon in the UK due to being outcompeted by the larger brown rats. In the UK, they’re most commonly seen in seaports and coastal areas where they live in abandoned buildings
• Size: Black rats are between 26-40 cm 
• Population and reproduction: Female black rats give birth to up to 5 litters a year, with each litter having between 5-8 pups
• Behaviour: Like brown rats, black rats are nocturnal

Striped field mouse

The striped field mouse (SFM) was the first rodent from which scientists discovered the hantavirus.³ SFM are known to carry Hantaan, Dobrava and Saaremaa hantavirus, with Hantaan being the first hantavirus to be discovered.^3,5,6 They are found in Eastern Europe and throughout Central and East Asia. 

Characteristics of the striped field mice 

• Habitat: SFM are found in urban areas, forests and wetlands in moderate climates
• Size: SFM are small mice, including their tail, they can be up to 12 cm long. 
• Population and reproduction: SFM have up to 5 litters a year, each with up to 6 pups
• Behaviour: SFM are active during the day and night, depending on the season. During colder months, they are more active during the day, and during warmer months, they are more active at night

Preventative measures 

Half of hantavirus infections happen after being exposed to the virus at home, and around 10% are due to exposure at work.¹ Farmers, for example, are especially vulnerable because rats are often found on farms.¹ To help prevent the spread of hantavirus, the following practices can be implemented:

• Setting traps 
• Blocking rodent access 
• Airing out spaces that haven’t been used in a while 
• Removing materials that rodents can use to create nests 

If rodent droppings are found, then the following methods can be used to keep yourself safe: 

• Wearing gloves or a mask 
• Washing hands with soap and water after exposure 
• Cleaning the area
• Spraying any nests with a disinfectant before cleaning them 

Summary 

Hantavirus is a group of viruses primarily transmitted to humans through contact with infected rodents. Different rodent species are associated with specific strains of the virus, which can lead to distinct illnesses such as hantavirus pulmonary syndrome, haemorrhagic fever with renal syndrome, and nephropathia epidemica.

Rodents such as the bank vole, brown rat, black rat, and striped field mouse serve as the main reservoirs of the virus. These animals commonly inhabit areas close to human dwellings, increasing the risk of exposure. 

Although person-to-person transmission is extremely rare, it has been documented with the Andes virus in South America. Preventative measures such as effective rodent control, safe cleaning practices, and proper ventilation of enclosed spaces are essential in reducing the risk of infection.