Hendra virus disease

Notification requirement for Hendra virus disease

Notification is not required. However, any new cases of this emerging virus should be reported to the department as a matter of urgency.

Primary school and children’s services centre exclusion for Hendra virus disease

Exclusion is not applicable.

Infectious agent of Hendra virus disease

Hendra virus is a member of the genus Henipavirus, a new class of virus in the family Paramyxoviridae.

Hendra virus is an emerging zoonotic virus, which means that it can transfer from animals to people. Hendra virus can cause disease in horses but only rarely in humans. The fatality rate in horses is around 75 per cent.

Hendra virus was first described in 1994 during an outbreak in the suburb of Hendra in Brisbane, Queensland. More than 40 outbreaks of Hendra virus disease have occurred since September 1994. Most outbreaks have occurred in Queensland, and some in northern New South Wales. Some outbreaks have involved humans, with seven confirmed human cases, including four deaths. The human case-fatality rate is 60 per cent, although the disease is rare.

There is no human vaccine for Hendra virus disease.

Identification of Hendra virus disease

Clinical features

Human infections with Hendra virus range from mild influenza-like illness to fatal respiratory disease (pneumonia) or neurological disease (aseptic meningitis and encephalitis). Infected people initially develop fever, headaches, myalgia (muscle pain), sore throat and dry cough. They may also have enlarged lymph nodes, lethargy, drowsiness, disorientation and vertigo (sensation of dizziness).

Diagnosis

Hendra virus can be detected by quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) assays of blood or urine samples, nasal or oropharyngeal swabs, or tissue samples.

Samples taken early during the incubation period may test qRT-PCR negative, and it may be necessary to repeat the sampling.

Results from initial testing are usually available within 24–48 hours.

In Victoria, testing of humans and horses is available through the CSIRO Australian Animal Health Laboratory (AAHL) in Geelong.

Serological tests, such as indirect enzyme-linked immunosorbent assay (ELISA) for screening human and horse sera for the presence of antibodies to Hendra virus, and a virus neutralisation test, may be used for antibody detection in any species. The diagnostic sensitivity of the ELISA is not well established.

Incubation period of Hendra virus

The incubation period ranges from 5 to 21 days.

Public health significance and occurrence of Hendra virus disease

Hendra virus disease is a public health concern because there is the potential for further spread, and the virus has the ability to cause disease and death in people.

It is not clear how horses become infected from flying foxes. However, research suggests that the most likely mode of transmission is ingestion by horses of pasture and feed contaminated with urine, faeces, saliva or birthing products from infected fruit bats (Australian flying foxes).

The risk of transmission to horses is increased during flying fox reproductive periods and times when the colonies are undergoing nutritional or other stress.

Transmission of the virus between horses appears to be more likely in horses kept in close proximity. However, companion horses in paddocks have on occasion been infected.

Hendra virus may survive on fomites for short periods. Infected horses excrete viral RNA through nasal discharge before the onset of clinical signs.

The virus is not easily transmitted to humans. Transmission requires direct physical contact with the excretions, secretions and body fluids (e.g. nasal discharge or blood) from an infected or dead horse.

Other animal species, including cats, dogs, guinea pigs, horses and pigs, can be experimentally infected. Recently, a dog was found to have natural infection (presence of antibodies) without symptoms of disease.

Reservoir of Hendra virus

Fruit bats (Australian flying foxes) of the family Pteropodidae – particularly species belonging to the genus Pteropus – are the natural host for Hendra virus, although there is no disease that manifests in these fruit bats.

All species of fruit bats are susceptible. Antibody to Hendra virus has been found in 20–50 per cent of fruit bats in mainland Australian populations.

Mode of transmission of Hendra virus

Hendra virus is transmitted to people through close contact with infected horses or their body fluids. The most likely mode of transmission is via droplet or contact transmission, with substantial direct exposure, from respiratory secretions or blood to mucous membranes or nonintact skin of humans.

Direct or indirect exposure to respiratory secretions, blood or other body fluids may contribute to the overall transmission risk.

To date, no human-to-human, human-to-horse or fruit bat-to-human transmission of Hendra virus has been documented.

Period of communicability of Hendra virus disease

There is no evidence of person-to-person transmission.

Horses should be considered potentially infectious from 72 hours before the onset of clinical signs until death (disease or euthanasia) and safe disposal of the carcass.

Susceptibility and resistance to Hendra virus disease

Unknown, but all humans should be considered susceptible.

Control measures for Hendra virus disease

Preventive measures

People who are most at risk include horse owners, veterinary personnel, horse dentists, farriers and other people with close contact with horses.

To minimise the risk of exposure, good hygiene practices should be used, and personal protective equipment, such as gloves, gowns, masks and protective eyewear, should be routinely worn by people:

• when handling or having contact with a sick horse, or a horse that may have been exposed to fluids from flying foxes
• when handling sick animals or their tissues
• during postmortem examination.

Procedures to avoid contamination of premises and equipment should be developed. Staff should receive appropriate education and training in infection control precautions and environmental control measures.

When examining an ill horse or horses, a risk assessment should be conducted for the likelihood of Hendra virus to avoid unnecessary exposure and to determine the infection control precautions to be taken.

Horse handlers should have good personal hygiene, including covering cuts and abrasions with an occlusive dressing, and performing hand hygiene after contact with animals.

In Australia, when Hendra virus is suspected in a horse, an inspector from the livestock health and pest authority or department of primary industries must be notified.

Control of a human case

Seek expert advice from an infectious diseases physician.

No licensed therapeutics are available to treat Hendra virus disease in humans, although a neutralising human monoclonal antibody that recognises the Hendra virus G surface glycoprotein is under review for Hendra virus infections. Current treatment for Hendra virus disease in humans is supportive.

Standard and droplet precautions should be implemented when caring for suspected or confirmed human cases of Hendra virus disease.

Control of human contacts

For all people at risk, information is provided and testing is undertaken on a case-by-case basis. Where possible, an infectious diseases physician should be involved in patient management.

qRT-PCR assays are used to exclude Hendra virus in symptomatic contacts.

For asymptomatic contacts, serology testing is performed at baseline, and 3 and 6 weeks after exposure (earlier if symptomatic).

Control of environment

Horse owners and carers can protect horses from becoming infected with Hendra virus by reducing exposure to bats, by placing feed bins and water troughs under cover, and away from areas where bats feed or roost.

Attempts to move bat populations should be avoided, as this may further stress the population and increase the secretion of Hendra virus.

Outbreak measures for Hendra virus disease

Follow the Australian Government Department of Health’s Hendra virus: national guidelines for public health units, and contact Communicable Disease Prevention and Control, Department of Health, on 1300 651 160.

Respond to a confirmed human or equine case, or where heightened suspicion of infection in a horse exists, as advised by the relevant animal health authority, immediately on notification.

Ensure that appropriate infection control measures are in place.

Ensure that liaison with an infectious diseases physician has occurred for confirmed human cases.