A four-year-old boy died of acute encephalitis syndrome (AES) while more cases surfaced after a fortnight-long lull.

Five children have been admitted to the Shri Krishna Medical College and Hospital (SKMCH) in a serious condition in the past 24 hours.

Deputy superintendent Sunil Kumar Shahi said: "Those admitted have been confirmed as AES patients after minute investigation and pathological tests."

This afternoon, one Dipak Kumar (4) of Jitwara village in Madhuban area of Motihari district died. Chief medical officer-cum-civil surgeon Giyan Bhushan said he has sent an SOS to the health department about fresh occurrence of cases.

The health department is a bit relaxed this year, as there have been fewer cases of AES in comparison to last year. However, 80 patients from North Bihar districts have been admitted with AES while 21 deaths have been reported in the course of treatment at SKMCH and Kejriwal Maternity Clinic.

The condition of the ones admitted in the past 24 hours is considered to be extremely critical. The affected children hail from the lower strata of society and have been admitted to SKMCH in a very advanced stage of the killer disease.

The health department is in a state of tizzy as all the five are confirmed cases of AES, said the CMO.

Dr Bhushan said the Centre of Disease Control, Atlanta, in US, had once again failed to trace out the viruses this year.

Now, experts including Padmini, who looks after cases of AES in Muzaffarpur, is focusing on "excessive heat and high temperature", as one of the factors behind the outbreak of AES.

Speaking to The Telegraph, Sahni said he has handed over a detailed case history of children caught with symptoms of encephalitis in the last 10 years to the team of Centre for Disease Control, US, Atlanta this year.

He also requested internationally acclaimed experts on AES, including Padmini and T. Jacob John of the Christian Medical College in Vellore to help him with his work.

The state health department has engaged the latter for conducting research and investigations to detect the viruses.

This year, it has been observed that children are contracting the disease, mostly, at night and not during the early hours of the day like was the case a year ago . They have been kept in the intensive care unit of pediatrics ward of the hospital.

Principal secretary of the health department Brajesh Mehrotra said: "Encephalitis experts are at work to find out more about the virus."

He is in constant touch with the health officials who are assisting him to detect the virus.

AES is a group of clinical neurologic manifestation caused by wide range of viruses, bacteria, fungus, parasites, spirochetes, chemical and toxins.

Last year, 163 deaths from among 864 children who were affected by the disease had been reported in north Bihar alone.