MANILA, Philippines --The Department of Health is monitoring the condition of at least 77 people who have shown symptoms of typhoid fever, an official said.

Dr. Eric Tayag, head of the DOH National Epidemiology Center, said the patients, who have experienced fever for over five days, diarrhea or constipation, mostly came from Barangay (village) Ungos, Real town in Quezon province. They have since been confined at a hospital in nearby Infanta town, he added.

"We are waiting for the updated report. It is hard to gather data because the area is far," said Tayag in a phone interview, noting that they have gathered water samples from the area to check whether the patients' water source had been contaminated. He said most of the patients relied on deep-well water.

Typhoid fever is a disease caused by the bacterium Salmonella typh and affects about 21.5 million people each year, according to medical website Centers of Disease Control and Prevention.

The illness can be prevented by frequent handwashing or by boiling the drinking water before consumption.