One person died and more than 400 were admitted to hospital in southern India because of an unidentified infection that caused many to fall unconscious after seizures and nausea, a senior health department official said on Monday.
Government and medical authorities in the southern state of Andhra Pradesh said that more than 200 people were discharged at the weekend and that tests had ruled out Covid-19, the infection caused by the coronavirus. Further serological tests are under way.
"The causes of the outbreak are not known yet," the state government said, but revealed that people in all age groups appeared prone to the infection.
Separately, India's federal health ministry said on Monday it would send a team of three medical experts to investigate the outbreak, which has infected more than 300 children.
"The children reportedly suffered from dizziness, fainting spells, headache and vomiting," the ministry said. A door-to-door survey was also under way.
A medical officer at Eluru Government Hospital told The Indian Express how some patients reacted.
“The people who fell sick, especially the children, suddenly started vomiting after complaining of burning eyes," the officer said. "Some of them fainted or suffered bouts of seizures."
The state health department was alerted to the first case over the weekend after the death of a 45-year old man, said Geeta Prasadini, a public health director in Andhra Pradesh.
"We have taken the patients' blood samples for serological investigation and bacterial investigation to rule out any type of meningitis," Ms Prasadini told Reuters.
Authorities were investigating water supplies at 20 sites in the city of Eluru where the outbreak was first reported as well as neighbouring areas, she said.
The opposition Telugu Desam Party called for a full inquiry into the incident.