Health authorities declined to comment on whether the sickness could be the bird flu that has broken out in several other parts of Asia, but a livestock official said there had been no reports of sick chickens.
"It is too early to comment on whether it is bird flu while the matter is still under investigation," said Abd al-Faiz, a professor of medicine at Dhaka Medical College Hospital.
The disease has affected people in villages in Faridpur district, 150km north of the capital, Dhaka.
Patients, most of them young boys, suffer from high fever, headache and vomiting before becoming unconscious. Some also suffered from diarrhoea, doctors said.
Three out of five patients admitted to the Dhaka Medical College Hospital with the symptoms had died in the past three days, doctors said.
"We are worried by the sudden spread of the mysterious disease and so far have not been able to identify it"
A Dhaka Medical College Hospital doctor
Health officials and newspapers said nine others had died of the disease since 17 January, most of them in Faridpur district.
"We are worried by the sudden spread of the mysterious disease and so far have not been able to identify it," said another Dhaka Medical College Hospital doctor who declined to be identified.
The government was taking steps to track the disease down, said Health Minister Khandakar Musharraf Husayn.
"We have formed an expert committee to visit affected areas and collect samples, which may be sent to the US Centre for
Disease Control for tests," the minister said.
Bird flu has sprung up in Thailand, Taiwan, Japan, South Korea, Cambodia and Vietnam in recent months.
Six people have died in Vietnam and two human cases have been confirmed in Thailand. Millions of chickens have died of the disease or have been killed as authorities struggle to stamp it out.
"There are no reports of abnormal deaths of poultry here. We have inquired about this with poultry owners following the mysterious deaths"
Narayan Chandra Roy,
District livestock officer
But there had been no reports of sick chickens in Faridpur district, a livestock official said.
"There are no reports of abnormal deaths of poultry here. We have inquired about this with poultry owners following the mysterious deaths," district livestock officer, Narayan Chandra Roy, told Reuters.
Officials at the International Centre for Diarrhoeal Diseases Research, Bangladesh, were also investigating the disease.
"We have yet to identify it though we suspect it's a viral illness," said one centre official who declined to be identified.