Hendra virus - what are the signs and symptoms?
Hendra virus was discovered following an outbreak of illness in horses in a large racing stable in the suburb of Hendra, Brisbane in 1994.
The natural host for Hendra virus is the flying fox.
The virus can spread from flying foxes to horses, horses to horses and, rarely, from horses to people.
Since Hendra virus was identified in 1994, more than 60 horses are known to have been infected.
These animals have either died as a direct result of their infection or have been euthanised.
Several hundred people have been exposed to Hendra virus infected horses but have not been infected.
However, seven people have been confirmed to have Hendra virus following high levels of exposure to infected horses. Four of these people died, the most recent in 2009.
In July 2011 a single dog on a property where three horses were infected with Hendra virus had a positive blood test that showed evidence of exposure to Hendra virus.
The dog showed no signs of illness.
This was the first reported case of Hendra virus antibody detection in a dog outside of an experimental setting.
Research and testing of many other animals and insects has shown no evidence of Hendra virus occurring naturally in any other species.
Disease in humans
People infected by the Hendra virus have become unwell with:
- An influenza-like illness with symptoms such as fever, cough, sore throat, headache and tiredness (which led to pneumonia in one case)
- Encephalitis (inflammation of the brain) with symptoms such as headache, high fever and drowsiness, which progressed to convulsions and/or coma.
The time from exposure to a sick horse until the start of illness in humans has varied between 5 and 21 days.
Disease in horses
Hendra virus infection in horses can produce a wide range of signs and is often difficult to recognise.
Early signs can include fever, increased heart rate and restlessness.
Other common features may include difficulty breathing and/or weakness and neurological signs such as uncoordinated gait and muscle twitching, quickly leading to death in most cases.
While the exact route of infection is unknown, it is thought that horses may contract Hendra virus infection from eating matter recently contaminated with flying fox urine, saliva or birth products. Spread of infection to other horses can then happen.
Spread is possible wherever horses have close contact with body fluids of an infected horse.
Small amounts of the virus may be present in a horse's body fluids, particularly nasal secretions, for a few days before they become sick.
The seven confirmed human cases all became infected following high level exposures to respiratory secretions and/or blood of a horse infected with Hendra virus, such as assisting with post mortem examination of a dead horse without appropriate personal protective equipment (PPE), performing certain veterinary procedures or having extensive exposure to respiratory secretions without appropriate PPE.
Other people have reported similar contact with infected horses but have remained well and their blood tests have shown no evidence of infection. No one with a lower level exposure (e.g. grooming, feeding, patting) has ever developed Hendra virus infection or shown evidence of infection in blood tests.
There is no evidence of human to human transmission.
People who have had contact with a person with Hendra virus infection, including health care workers and family members, have been tested and shown no evidence of the virus.
There is no evidence that the virus can be passed directly from flying foxes to humans, from dogs to humans, from the environment to humans, from humans to horses or float in the air.
Hendra virus is killed by heat, drying and cleaning with detergents.
It is important that people who have been in close contact with a horse infected with Hendra virus monitor their health.
A person who becomes unwell in the weeks after close contact with an infected horse should contact their public health unit and seek medical advice promptly.
Tests may be recommended to rule out Hendra virus as the cause of their illness.
In most cases, a cause other than Hendra virus will be found.
A symptomatic person may be admitted to hospital under the care of an infectious disease physician for close monitoring while waiting for test results.
If Hendra virus infection develops cases are managed supportively in hospital.
There is no known specific treatment for Hendra virus infection.
To date, antiviral medications have not been effective but three people have recovered from infections with general medical support.
People who have had high level exposures to the body fluids of an infected horse may be offered experimental treatment with a type of antibody that may prevent infection.
Preventing horse infection
Research into the development of a vaccine for horses against Hendra virus is well under way.
Steps can be taken to decrease the risk of Hendra virus infection in horses. It is important to protect horse food and water from contamination by flying fox fluids, isolate sick horses early while awaiting test results, and pay attention to standard hygiene and cleaning practices.
More information is available from Biosecurity Queensland or call 13 25 23 and Workplace Health & Safety Queensland or call 1300 369 915.
Preventing human infection
As a horse may be infectious with Hendra virus before becoming noticeably unwell, it is important to pay attention to standard hygiene practices when interacting with any horse.
Horses should never be kissed on the muzzle.
Hands should be cleaned regularly after touching horses, particularly before eating, smoking or touching one's eyes, nose or mouth.
Wounds should be covered with a waterproof dressing.
The use of personal protective equipment is recommended when it is likely that a person will come into contact with body fluids from any horse.
See Biosecurity Queensland and Workplace Health & Safety Queenslandfor more information.
If body fluids or manure from a horse gets on unprotected skin the area should be washed with soap and water as soon as possible.
If the exposure involves a cut or puncture wound, gently encourage bleeding and then wash the area with soap and water.
Where water is not available, wipe the area clean, then use a waterless cleanser such as alcohol based gel.
If eyes are contaminated, gently but thoroughly rinse open eyes with water or normal saline for at least 30 seconds.
If body fluids get in the mouth, spit the fluid out and then rinse the mouth with water several times.
If a horse becomes unwell and Hendra virus infection may be a possibility, as few people as possible should care for the horse until the infection is ruled out.
Children should be kept away from the horse.
Appropriate personal protective equipment which prevents contamination of the skin, eyes, nose or mouth of people by the horse's body fluids should be worn if close contact with the sick horse is considered essential.
Although there is no evidence of human to human transmission, close contact with the body fluids of a person who is unwell with possible Hendra virus infection should be avoided.
In hospital, healthcare workers will take routine precautions which include the use of personal protective equipment.
In home settings, particular attention should be given to standard hygiene measures such as regular hand washing.
People exposed to Hendra virus should not donate blood or other tissue until they are cleared of infection. Confirmed cases should never donate blood or any other tissue, even if they fully recover.
Suspected cases of Hendra virus infection in horses should be notified urgently to Biosecurity Queensland on 13 25 23 (during business hours) or 1800 675 888 (24-hour Emergency Animal Disease Watch Hotline).
Pathology laboratories are required to urgently notify all requests for Hendra virus testing in humans to the appropriate public health unit.
Public health response
When a horse is strongly suspected or confirmed to be infected with Hendra virus, Biosecurity Queensland will notify Queensland Health and take urgent measures to minimise risk to other people and other horses.
Public health staff will seek to identify all people who may have been exposed to an infectious horse and conduct a detailed assessment of their level of exposure.
People at risk of infection will be provided with information about Hendra virus and advised of appropriate ongoing management.
If you have had recent exposure to an infected horse and have not been contacted by public health staff, please telephone your nearest public health unit or 13 HEALTH (13 43 25 84).