Human Hendra virus encephalitis associated with equine outbreak, Australia, 2008.

Area of Science:

• Veterinary Virology
• Zoonotic Diseases
• Infectious Disease Epidemiology

Background:

• Hendra virus (HeV) is a zoonotic virus endemic in Australia, known to cause severe respiratory and neurological disease in horses and fatal encephalitis in humans.
• Previous HeV outbreaks primarily involved respiratory signs in horses and limited human transmission, posing significant veterinary and public health risks.

Observation:

• A recent HeV outbreak in a Brisbane veterinary clinic resulted in 5 equine and 2 human infections.
• Infected horses exhibited predominantly encephalitic signs, differing from typical respiratory presentations in prior outbreaks.
• Two veterinary staff members developed influenza-like symptoms followed by encephalitis 9-16 days post-exposure to infected horses; one patient died.

Findings:

• Ribavirin treatment was administered to both human patients, achieving serum and cerebrospinal fluid levels below the isolate's 90% inhibitory concentration (64 mg/L).
• The attack rate among veterinary clinic staff exposed to infected horses was 10%.
• Genetic analysis revealed heterogeneity in the HeV isolate from this outbreak compared to geographically distant and previous HeV isolates.

Implications:

• This outbreak underscores the evolving clinical presentation of Hendra virus in horses and the potential for severe neurological disease in humans.
• The findings highlight the importance of considering HeV in differential diagnoses for equine neurological disease and potential human exposure.
• Genetic heterogeneity suggests ongoing viral evolution, emphasizing the need for continuous surveillance and adaptive public health strategies to manage this zoonotic threat.