“The number is just the tip of the iceberg,” Dr Bibek Kumar Lal, director at the division, told the Post. “A lot of people might have been infected, as all hospitals do not report to us.”

Another reason why the division suspects the number of dengue cases could be higher than reported is that the people with mild symptoms do not visit the hospital.

Doctors say though 75 to 90 per cent of dengue cases are asymptomatic, those patients could still infect others.

“Only those who have complications go to the hospital,” Lal said.

According to the division, most of the dengue cases reported in the Valley are indigenous—that is to say, they contracted the virus locally.

If the patients do not have a history of travelling to dengue-affected areas for the last one week and get infected with the deadly virus, doctors call it an indigenous case. The incubation period of the dengue virus is one week, which means when a dengue-causing mosquito bites a healthy person, symptoms surface within one week.

Before this, indigenous dengue cases were reported among people from Kapurdhara, Baneshwor, Tinkune, Tahachal, Teku, Sanobharyang, Balaju, Swayambhu, Lagan and Ason areas.

Following the rise in the number of indigenous dengue cases, the division had held an emergency meeting with the representatives of Provincial Health Directorate of Province 3 and Provincial Health Offices of all three districts in the Valley—Kathmandu, Lalitpur and Bhaktapur— on Sunday. The meeting had discussed various measures to contain the spread of the disease.

Earlier, two health experts from the World Health Organization had warned of possible dengue outbreak in the Valley after they found a large number of larvae and pupae of dengue-causing Aedes aegypti and Aedes albopictus mosquitoes.

Dengue-causing mosquitoes breed in clean water and bite people in daylight. Due to an acute drinking water crisis, people in the Valley store water in jars and pots, which could be ideal breeding grounds for these mosquitoes. Uncovered water tanks and discarded plastic cups and bottles could also shelter dengue-carrying mosquitoes.

According to doctors, mild to high fever, severe muscle pain, rashes, severe headache, and pain in eyes are some of the symptoms of dengue.

The WHO says there is no specific treatment for severe dengue, but early detection and access to proper medical care can lower the fatality rate.