Short Note on Dengue in Nepal

Nepal is endemic for many vector-borne diseases, including malaria, kala-azar, Japanese encephalitis, and lymphatic filariasis. Diseases related with poverty are major public health problem. This is further compounded by deteriorating environmental conditions with tropical/sub-tropical climate. It is also aggravated by increased vector amplification and disease transmission due to urbanization, increasing population density and climate change effects. In recent years, there are increasing formal and informal reports of new emerging and re-emerging infectious diseases. Among those, Dengue fever (DF) which is proved to be associated with high morbidity and mortality, is posing increasing public health threat. This means that preventive and control measures against DF cannot be effective, if we lack good epidemiological understanding of the disease in question.

There was no documented indigenous case of dengue infection in Nepal until the Sept-Oct outbreak of 2006. During this outbreak, all Dengue serotypes were identified from few Hill (Kathmandu-no history of travel) and Terai districts (Banke, Parsa, Dhading, Jhapa, Rupendehi, Dang and Kapilbastu) of Nepal. (Malla S, Thakur GD, Shrestha SK, Banerjee MK, Thapa LB, Gongal G, Ghimire P, Upadhyay BP, Gautam P, Khanal S, Nisaluk A, Jerman RG, Gibbons RV. Identification of all Dengue serotypes in Nepal. Emerging Infectious Diseases 2008; 14 (10): 1669-70). The first report of dengue virus isolation was in 2008 involving a Japanese patient returning from Nepal in October 2004. According to genomic study, the virus was closest to a dengue virus from India. Basu Dev Pandey et al (August – November 2006) also reported serologically confirmed DF from Hill (Kathmandu and Sindhuli) and Terai districts (Bardiya, Salyan, Birgunj and Dang) among febrile patients. Only 1 case had travel history outside of their residence. Many entomological studies of mosquitoes carried since eighties to recent, have revealed the presence of dengue vectors in major urban areas of Hill and Terai districts. Previously no Aedes aegypti was recorded in Nepal. These evidences strongly suggest the existence of an epidemic cycle of Dengue in Nepal. 

However, there are few important points that need to be taken into consideration.

• Inadequate evidence to explain actual burden and epidemiological characteristics of the dengue fever in the Nepal.
• Health professionals do not usually consider dengue as a differential. There is also under or no reporting in the absence of diagnostic facilities at the field level. It may be reported as viral fever or pyrexia of unknown origin (PUO).
• Nepal has no dengue surveillance programs, and lack effective preventive and control measures against DF. 
• It is alarming situation that the DF is observed in patients from hilly districts with no travel history.