JAPANESE encephalitis (JE) is mainly spread by mosquitoes with birds and domestic pigs serving as amplifying hosts.

It usually occurs in rural or agricultural areas and is often associated with rice or pig farming.

Most JE virus infections are mild, with fever and headache, or without apparent symptoms.

However, approximately 1 in 250 infections results in severe diseases characterised by rapid onset of high fever, headache, neck stiffness, disorientation, coma, seizures, spastic paralysis and death.

According to the World Health Organization (WHO), the case fatality rate can be as high as 60% among those with disease symptoms, and 30% of those who survive suffer lasting damage to the central nervous system.

Symptoms can take up to two weeks to appear.

Encephalitis occurs mainly in young children because older children and adults have usually been infected and are immune, says Dr Zulkifli Ismail, a consultant paediatrician with the Malaysian Paediatric Association.

A 1997-2006 hospital-based surveillance system for JE  in Sarawak found that 92% of 133 cases were children aged 12 years or younger.

An outbreak occurred in Penang in 1988 (nine cases and four deaths), in the Serian district of Sarawak in 1992 (nine cases, four deaths) and Langkawi in 1974 (10 cases, two deaths).

Less than two dozen cases are reported annually in recent years, according to the Health Ministry.

About 68,000 JE cases are reported worldwide annually, according to WHO.

In Sarawak, a case of JE was detected at the same time of a rabies outbreak. On Tuesday, a pair of rabies-infected siblings in Sarawak died within minutes of each other at the Sarawak General Hospital.

The girl, 6, and her brother, 4, were from Kampung Paon, Sungai Rimu, about 70km from Kuching in the Serian district.

A third rabies-infected patient, a 7-year-old girl from  Kampung Lebur, Gedong in the Simunjan district, is critically ill. 

The Sarawak government declared five villages in the Serian-Simunjan districts as rabies-affected on Tuesday. – July 6, 2017.