LAHORE: Four more patients of dengue virus fever died while 277 new cases occurred in Punjab in the last 24 hours. The death toll by dengue hemorrhagic fever in the province in this season has surged to 90 with two more deaths in Lahore and one each in Gujranwala and Attock, according to the health department. Of the new cases, 225 were reported in Lahore alone, according to provincial health secretary Imran Sikandar Baloch. The number of dengue cases reported in the province thus far this season has risen to 20,835. Lahore has so far reported 15,380 cases of dengue fever during the current season. A total of 1854 patients of dengue fever are being currently treated at different hospitals across the province, 1215 of them in Lahore, the secretary said. Moreover, Islamabad has reported 23 more dengue fever cases during the past 24 hours, the district health officer (DHO) said. The DHO said that 11 cases of the disease were reported in the rural areas and 12 in the urban areas. In Islamabad 19 persons have died of the disease. Dengue is a mosquito-borne viral infection that is common in warm, tropical climates and often peaks during rainy seasons, states the World Health Organisation (WHO). Once bitten by a dengue-infected mosquito, the virus takes four-10 days to affect the body. Its symptoms can be mild, similar to the common flu, or severe such as fever, headaches, pain behind the eyes and nausea.