Australia is facing its first-ever major outbreak of Japanese encephalitis. Japanese encephalitis is the most severe form of illness caused by the Japanese encephalitis virus (JEV). The disease is first discovered in southern regions of Australia, spreading to piggeries in Victoria, South Australia, New South Wales and Queensland.
There have been 20 confirmed cases in humans so far and two people have died. About 99% of people infected with JEV will have no symptoms or very mild symptoms. But in less than 1% of cases, it can become serious.
What is Japanese encephalitis? JEV is an infection that can be transmitted to people if they are bitten by a mosquito carrying the virus. It cannot be transmitted from person to person. Mosquitoes become infected if they bite an infected bird in the wild (usually wetland wading birds) or an infected mammal such as a pig.
Pigs are the greatest risk as a source of infection for humans, as they have very high levels of virus in their blood when infected. Mosquitoes bite infected pigs, then bite humans, infecting us. But people don’t get the infection directly from interacting with pigs or eating pork, because JEV is transmitted by mosquitoes.
Encephalitis means inflammation of the brain and myelitis means inflammation of the spinal cord. This inflammation of the brain or spinal cord is most often triggered by an infection. JEV is the main infection responsible for encephalitis in South and East Asia, causing approximately 50,000 to 70,000 cases of encephalitis and approximately 15,000 to 20,000 deaths each year. There are many other infectious causes of encephalitis. The specific features of the disease depend on the cause, but these features often overlap. Diagnosing a specific cause may require testing multiple samples repeatedly.
Diagnosis of JEV encephalitis requires direct detection of the virus by PCR testing in blood or fluid surrounding the brain or spinal cord, which is taken from the lower back. Or, it can be detected by the body’s response to the virus by testing immune proteins (called antibodies) in the blood or in the fluid surrounding the brain or spinal cord.
What does JEV do to your body? If a person is bitten by an infected mosquito, the virus is injected into the skin. The first cycle of replication then begins inside our skin cells. The virus is then transferred to the local lymph nodes, for example under the arm or in the neck. This process takes about a week. The infection can be stopped by our immune system at this point.
A second round of replication can cause the virus to spread through our bloodstream. Again, the virus can be stopped by our immune system in this phase, but this phase can be associated with symptoms such as fever, rash, body aches and pains, vomiting or diarrhea. This phase lasts about one to four days. When JEV spreads in the blood, the virus can enter the brain or spinal cord. This occurs in less than 1% of infections, but if it does, JEV replicates efficiently in the brain and spinal cord.
The virus itself and the resulting inflammation impair brain and spinal cord function, often irreversibly. The main symptoms include: fever, headache, confusion, convulsions or convulsions and weakness of the limbs.
Inflammation also leads to swelling, and swelling of the brain within the closed skull can lead to death. All forms of encephalitis can be serious and lead to brain damage, but JEV has been shown to be one of the most serious forms, and potentially more serious in young children than in adults.
For the 1% of people in whom JEV infection progresses to encephalitis, it results in death in about 20% of cases, and about half of survivors will have some kind of neurological disability.
What should I do if I think I have been exposed? Exposure to mosquitoes in and around parts of NSW with large pig populations is the main risk, although at present only a relatively small number of cases have been identified in Australia.
If you think you have been exposed and have developed any of the symptoms, you should see your doctor. If you or someone you know has the most severe symptoms of encephalitis, you should seek urgent evaluation. Unfortunately, there is no specific treatment that has been shown to be effective in treating JEV. However, the high quality supportive care available in Australian hospitals improves outcomes.
Prevention is better than cure. So now is the time to do what you can to avoid mosquito bites. In addition, there are effective vaccines. State and federal public health authorities are currently working on how best to use them to control the current outbreak and prevent disease.
At this time, the vaccine is free and has been prioritized for certain groups, including people: who must work or visit pig barns or slaughterhouses, who work directly or indirectly with mosquitoes, such as environmental health workers and laboratory workers who may be exposed to the virus. (The conversation)
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