Kathmandu district recorded 254 dengue cases till Sunday. But by Tuesday that number had surged to 1,170, The Himalayan Times reported.
The number of dengue patients in two other districts of Kathmandu valley, however, has remained stable over the past two days.
"One of the major reasons for rapid spread of the disease in Kathmandu district is poor sanitation," said Baburam Marasini, former director at Epidemiology and Disease Control Division.
"Moreover, many dengue patients from across the country are in Kathmandu for treatment. Since many public hospitals that treat dengue are located in Kathmandu district, chances of those not infected contracting the disease are very high," Marasini added.
This is the first time Kathmandu district has seen such a large number of dengue patients. The disease has also affected 55 other districts.
Till Tuesday, 5,095 people had tested positive for dengue across Nepal, up from 3,899 on Sunday.