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Indian Journal of Medical Microbiology, Vol. 28, No. 4, October-December, 2010, pp. 412 Correspondence Displacement of dengue virus type 3 and type 2 by dengue virus type 1 in Delhi during 2008 A Chakravarti, A Kumar, M Matlani Department of Microbiology, Maulana Azad Medical College, Bahadur Shah Zafar Marg, New Delhi - 110 002, India Date of Submission: 06-Apr-2010 Code Number: mb10123 PMID: 20966588 Dear Editor, Dengue infection is an emerging disease in India, with reported endemicity of all the four serotypes. Delhi has witnessed several outbreaks since 1967, out of which, 1996, 2003, and 2006 are the major ones. Reports from the previous years show that since 1996, DEN-2 and DEN-3 have been the major circulating serotypes during the various outbreaks. [1] However, our study in the year 2008, demonstrated DEN-1 to be the predominant serotype. This study included 1154 clinically suspected cases of dengue, attending the outpatient department or admitted in wards of our hospital, between July 2008 and December 2008. The patients were categorized as Dengue Fever (DF)/Dengue Hemorrhagic Fever (DHF) as per the WHO criteria.[2] The average age of the patients with dengue infection was 29 years (ranging from 2 to 65 years), of which 70% of the cases were men. The major clinical features were fever, arthralgia, myalgia, and retro-orbital pain, rash, gum bleeding. Epistaxis and malena were the common haemorrhagic manifestations. Out of 1154 cases 244 ( 21.14%) were positive for IgM antibodies by M-capture Elisa. Amongst the 170 cases who presented to the hospital within the first five days of illness, 23 showed the presence of dengue viral RNA by RT-PCR.[3] Out of 23 RT-PCR positive cases, DEN-1 was isolated in 20 cases, DEN-2 was isolated in two cases, and DEN-3 was isolated in a single patient, while DEN-4 was not isolated in any case. These findings suggest that DEN-1 had replaced DEN-2 and DEN-3 as the predominant type in the year 2008. Another important observation was that, out of 20 cases of DEN-1, 60% (12) of cases had DHF with severe haemorrhagic manifestations. These findings are in contrast to the previous studies, which reported DEN-1 to be associated with milder form of disease, while DEN-2 and DEN-3 were reported to cause dengue with severe haemorrhagic manifestations. [4] The findings of association of DEN-1 in 60% of DHF cases suggest that enhancement of virulence could have occurred due to some mutations in this particular serotype. Recently some studies from Peru have shown that sudden shifts in the circulating serotypes lead to major outbreak in that region. [5] The present study also highlights the change in circulating serotypes from DEN-2 and DEN-3 to DEN-1 in the year 2008. Although no outbreak occurred in the year 2009, DEN-1 may continue to circulate and mutate to acquire a more virulent nature, which could lead to an outbreak in future. Acknowledgment We are thankful to Department of Science and Technology (DST), Delhi for funding this study. References
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