Kunjin/West Nile virus infection - including symptoms, treatment and prevention

Kunjin is caused by infection with the Kunjin virus, which is now considered to be a variant of West Nile virus (another potentially serious illness spread by the bite of an infected mosquito).

Kunjin virus infection is a notifiable condition1

How Kunjin virus is spread

Kunjin virus is endemic (always present) in tropical parts of Australia, in birds. Illness in humans is rare and most reported cases occur in northern Australia.

The infection is spread from infected animals, including water birds and other birds, and mammals, to humans by mosquito bites.

Signs and symptoms of Kunjin virus infection

Most people with Kunjin virus infection have mild or no symptoms.

Symptoms of Kunjin virus infection may include:

  • fever
  • malaise (feeling of being unwell)
  • headache
  • muscle aches
  • swollen lymph nodes
  • fatigue
  • rash
  • swollen and aching joints.

Rarely infection may progress to encephalitis (infection or inflammation of the brain). 


Symptoms of encephalitis may include:

  • fever
  • rigors
  • headache
  • neck stiffness
  • irritability
  • confusion
  • drowsiness (excessive sleepiness)
  • seizures (fits).

Kunjin virus encephalitis is similar to Murray Valley encephalitis but is usually milder.

Diagnosis of Kunjin virus infection

Diagnosis is made by blood tests or by detecting Kunjin virus in CSF (cerebrospinal fluid: the fluid surrounding the brain and spinal cord).

Incubation period

(time between becoming infected and developing symptoms)

Unknown. Likely to be 2 to 6 days and may extend to 14 days.

Infectious period

(time during which an infected person can infect others)

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

Infection with Kunjin virus is thought to confer lifelong immunity.

Treatment for Kunjin virus infection

There is no specific treatment for Kunjin virus infection and no vaccine to prevent infection.

Prevention of Kunjin virus infection

  • Exclusion from childcare, preschool, school or work is not necessary but cases should avoid being bitten by mosquitoes while they are unwell.
  • There is no vaccine to prevent human infection by Kunjin virus.
  • Personal protection and the environmental management of mosquitoes are the keys to prevention. For tips on how to protect yourself, see Fight the Bite.

Useful links

1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as 'notifiable conditions'.