Hendra Virus

Hendra virus is a single-stranded, enveloped RNA virus that belongs to the Paramyxoviridae family and Henipavirus genus. It was first described in sick horses in a suburb of Brisbane, Australia in the 1990s. Hendra virus infection is a zoonotic disease (i.e., it can be transmitted from animals to humans) that primarily affects horses in the northeastern coast of Australia. Nonetheless, there have also been a small number of cases describing Hendra virus infection in humans. 

While Hendra virus mainly affects horses, the virus can also be transmitted from horses to humans if humans come into contact with an infected horse’s respiratory secretions or bodily fluids. The reservoir for Hendra virus is thought to be flying foxes or fruit bats of the genus Pteropus. The virus spreads to horses through contact with body fluids (e.g., saliva or urine) of bats infected with Hendra virus. Then, close contact between humans and infected horses leads to zoonotic disease transmission. To date, human-to-human transmission of Hendra virus has not been reported. 

The signs and symptoms of Hendra virus infection in horses and humans are similar and resemble symptoms seen in a flu-like illness. Initial signs and symptoms include fever, malaise, headache, myalgias, cough, shortness of breath, and loss of appetite. In some instances, Hendra virus infection may cause rapid onset of illness and rapid deterioration with severe respiratory symptoms (e.g., shortness of breath, respiratory failure). Rare neurological manifestations include encephalitis (i.e., inflammation of the brain) and meningitis (i.e., inflammation of the meninges). Hendra virus has an incubation period ranging from 9 to 16 days, which is the time between coming into contact with the virus and the first appearance of symptoms. 

Diagnosis of Hendra virus in humans begins with a thorough review of symptoms and risk factors (e.g., occupational exposure, close contact with horses, recent travel to high-risk areas). Diagnosis is confirmed through a throat or nasal swab and/or cerebrospinal fluid sample, followed by reverse transcriptase polymerase chain reaction (RT-PCR), a sequencing method that detects the genetic material of a pathogen (e.g., RNA from Hendra virus) and subsequently produces a genetic code (i.e., DNA) of the detected pathogen. Enzyme-linked immunosorbent assay (ELISA), which utilizes specific antibodies that can bind to a protein derivative of Hendra virus to confirm disease, can also be used. Samples taken from infected horses can also be sent to laboratories for further confirmation.

For humans, treatment is aimed at supportive care measures to improve symptom burden in both respiratory and neurologic involvement.  Supportive measures include adequate rest and hydration with oral fluids, and over-the-counter medications such as acetaminophen or ibuprofen to manage fever and alleviate muscle aches and pains. Saline nasal sprays and humidifiers may help with nasal congestion and salt water rinses can help relieve sore throat. If symptoms worsen with significant respiratory compromise (e.g., shortness of breath, wheezing), individuals should seek emergency medical attention immediately as they may require hospitalization for airway management. Treatment with ribavirin, an antiviral medication, and post-exposure therapy with a Hendra virus-neutralizing antibody are emerging strategies that are effective based on in vitro studies (i.e., studies conducted outside of a living organism). However, further clinical studies are needed to confirm their efficacy in humans. Even though Hendra virus infection is rare, the mortality rates are high. Of the seven reported causes of Hendra virus infection in humans, four (57%) individuals experienced death. Of note, for horses, there is a Hendra virus vaccine that can be administered to prevent re-infection and reduce the likelihood of human exposure. 

Individuals who work closely with horses, especially in regions where Hendra virus is prevalent (e.g., coastal and forested regions in Australia), should take preventative measures to minimize risks by using protective equipment, avoiding contact with sick horses, and implementing good hygiene, all of which reduce the risk of disease exposure. Additionally, there is an emergency animal disease hotline on 1-800-675-888 for individuals who have come into contact with infected horses with signs of illness. 

Hendra virus is a member of the Paramyxoviridae family and Henipavirus genus. The natural reservoir for Hendra virus is thought to be flying foxes or fruit bats of the genus Pteropus. The virus is spread to horses through contaminated body fluids (e.g., saliva or urine) of bats infected with Hendra virus. Then, close contact between humans and infected horses leads to zoonotic disease transmission.  In the seven reported cases of Hendra virus infection in humans, most showed signs and symptoms resembling a flu-like illness. However, Hendra virus infection can cause rapid onset of illness with rapid deterioration with severe respiratory symptoms. Rarely, there may also be neurologic manifestations. Diagnosis is confirmed through a nasal or throat swab sample which is then sent to the laboratory for further testing using techniques like RT-PCR or ELISA. Treatment is aimed at supportive care measures that improve the individual’s symptoms. While ribavirin and neutralizing antibodies have shown promise in in vitro testing, further clinical studies are needed to confirm their efficacy.