Topic: Hendra Virus Infection
Description
Hendra virus was discovered following an outbreak of illness 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 and, rarely, from horses to people. A single dog showed evidence of exposure to Hendra virus following contact with an infected horse in July 2011. However, research and testing of many other animals and insects has shown no evidence of Hendra virus occurring naturally in any other species.
More than 50 horses have been infected with Hendra virus. These animals have either died as a direct result of their infection or been euthanised. Several hundred people have been exposed to these horses but have not been infected.
Unfortunately, there have also been seven confirmed Hendra virus infections in humans, all in Queensland. Four of these people died, the most recent in 2009.
Symptoms
Disease in humans
People infected by the Hendra virus have become unwell with:
- an influenza-like illness (which led to pneumonia in one case) with symptoms such as fever, cough, sore throat, headache and tiredness
and/or - encephalitis (inflammation of the brain) with symptoms such as headache, high fever and drowsiness, which progressed to convulsions and/or coma and death.
The time from exposure to a sick horse until the start of illness in humans has been between five and 21 days.
Disease in horses
Hendra virus infection in horses can produce a wide range of signs. Early signs usually include fever, increased heart rate and restlessness. Other common features include difficulty breathing and/or weakness and neurological signs such as uncoordinated gait and muscle twitching, quickly leading to death in most cases.
Transmission
While the exact route of infection is unknown, it is thought that horses may contract Hendra virus infection from eating food recently contaminated by flying fox urine, saliva or birth products. Spread of infection to other horses can then follow. Spread happens more often when the sick horse is kept with other horses in a stable, but is possible wherever horses have close contact with body fluids from 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 close contact with respiratory secretions and/or blood from a horse infected with Hendra virus. Many people have reported similar contact with infected horses but have remained well and their blood tests have shown no evidence of infection.
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 can float in the air.
Hendra virus is killed by heat, drying and cleaning with detergents. Some disinfectant products are also effective against the virus.
Treatment
Research is being undertaken into monoclonal antibodies to see if they may be useful in preventing Hendra virus infection from developing in people with high level exposures.
A person who becomes unwell in the weeks after close contact with a Hendra-infected horse should seek medical advice promptly. Tests may be recommended to rule out the virus as the cause of their illness. In most cases, a cause other than Hendra virus will be found. Sometimes the person will be admitted to hospital for monitoring while waiting for test results. They will probably be admitted to hospital for close monitoring and if needed, intensive care if Hendra virus infection develops.
There is no known specific treatment for this infection. To date, antiviral medications have not been effective in treating Hendra virus infection but three people have recovered from infections with general medical support.
Prevention
Preventing horse infection
Research into the development of a horse vaccine against Hendra virus is well underway.
Steps can be taken to decrease the risk of Hendra infection in horses. It is important to protect horse food from contamination by flying fox fluids, isolate sick horses early while awaiting test results, and pay attention to standard hygiene and cleaning practices. Detailed information is available from Biosecurity Queensland or call 13 25 23, and also from the Queensland Horse Council.
Preventing human infection
It is important to pay attention to standard hygiene practices in all contact with horses because they may be infectious with Hendra virus before becoming noticeably unwell. Hands should be cleaned regularly while caring for horses, particularly before eating, smoking or touching the eyes, nose or mouth. Wounds should be covered with a waterproof dressing. Directly kissing a horse on the muzzle is strongly discouraged at any time and definitely should not occur if the horse is sick or quarantined. 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 for 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 or antiseptic. If eyes are contaminated then 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. It is strongly recommended that children are kept away from the horse. Appropriate personal protective equipment which prevents contamination of the skin, eyes, nose or mouth 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.
Notification
Suspected cases of Hendra virus infection in horses should be notified urgently to Biosecurity Queensland on 13 25 23 (during business hours) or the Emergency Animal Disease Watch Hotline on 1800 675 888 (24-hour hotline). Biosecurity Queensland will notify the appropriate public health unit of the situation if there is a high suspicion of Hendra virus infection.
Pathology laboratories are required to urgently notify all requests for Hendra virus testing in humans to the appropriate public health unit.
Help and assistance for human exposures to an infected horse
When a horse is diagnosed with Hendra virus infection, the local public health unit will work closely with Biosecurity Queensland, the property owners and property managers to identify people who may have been exposed. If you have had recent exposure to an infected horse and feel that you have not been identified, please telephone your nearest public health unit or look in the White Pages under 'Queensland Health' or contact 13 HEALTH (13 43 25 84).
Help and Assistance
Other resources
Biosecurity Queensland or call 13 25 23.
Information about Hendra virus for the general public, horse owners, horse handlers and veterinarians. The latest version of the Guidelines for veterinarians handling potential Hendra virus infections in horses is also available from this site.
Queensland Horse Council
Information for horse owners and handlers.
For more information
For other information or assistance regarding Hendra virus infection in humans please contact 13 HEALTH (13 43 25 84).
Last Updated: 22nd September, 2011
Date Valid to: 11th October, 2011
