Until this year. There have been hundreds of cases again — 719 as of Monday, with 152 deaths — all among poor children here in the Muzaffarpur lychee belt, in a heavily populated area of Bihar State. And this time, doctors say they are finding many cases in which lychees were not a factor.

The treatment epicenter is the Sri Krishna Medical College and Hospital in Muzaffarpur, where 102 of the deaths this year occurred. That amounts to a 27 percent fatality rate for the disease at that hospital, according to BrajMohan, the doctor in charge of a pediatric recovery ward there. On Friday, there were 65 children sharing 40 beds in his ward, and 16 mattresses in a corridor accommodated 30 others.

Those were the lucky ones, who survived the hospital’s three pediatric intensive care units.

Most of the children who got sick this time were younger than 5, and many were only 1 or 2 and still breastfeeding, said Dr. BrajMohan, who uses just one name. “They were hardly eating lychees at that age,” he said.

Many other doctors and officials at the hospital are also skeptical about the lychee theory.

“It must be some sort of virus or bacteria, we just haven’t detected it yet,” said J.P. Mandal, who, like Dr. BrajMohan, is a pediatrician and a medical professor. “You have to transport samples to labs at minus 80 degrees Celsius, when the temperatures outside are 45 degrees — no wonder we haven’t found it,” he added. (Forty-five degrees Celsius is 113 degrees Fahrenheit.)