A Comprehensive Prospective Study to Understand Chikungunya Infection in Delhi Region during 2010-2011

Abstract

INTRODUCTION: Chikungunya is an arbovirus causing febrile illness with high strike rate and is known for outbreaks in more than 60 countries globally. During 2010-2011 unusual high number of suspected Chikungunya infection patients attended AIIMS OPD, Delhi, India. The NCR region with its semiarid geography restricts arbovirus outbreaks to monsoon months and is previously known for Dengue outbreaks although Chikungunya outbreaks were previously unknown to the region. The surge in suspected Chikungunya infection cases indicates a possible outbreak in the NCR region. This comprehensive prospective and follow-up study was designed to understand the Chikungunya infection among patients attending AIIMS OPD during 2010-11. METHOD: During June 2010 to Dec 2011, 2346 blood samples were collected from outpatients and inpatients attending AIIMS OPD, New Delhi. Samples were grouped in acute and chronic cases. Some patients were also enrolled for year-long follow-up study. Serum samples were tested for CHIKV using PCR and for IgM antibodies to chikungunya virus by IgM-capture ELISA. Real-time PCR was performed targeting the E1 gene for viral load determination in patient sera. RESULT: CHIKV positivity of 35% (746/2112) in acute and 67% (156/234) in chronic suspected cases were found by ELISA. most affected patients belonged to the age group >30-45 yrs. and above in both genders. Acute confirmed cases included 383 (51.3%) females and 363 (48.7%) males and chronic includes 92 (58.9%) females and 64 (41.1%) males. Clinical symptoms include polyarthralgia, fever, and rashes. Maximum positivity was seen in Oct-Nov of both years. During follow-up study, 118 patients enrolled, persisting polyarthralgia and anti-CHIKV IgM was detected up to 2 years while circulating CHIKV was detected by PCR up to 3 months in few patients. CONCLUSION: Chikungunya virus has emerged in Delhi during 2010 and contributed to about 30-40% of fever and arthralgia. CHIKV prevalence is highest in post monsoon month of October. The virus can remain in blood circulation for weeks, while anti-CHIKV IgM can persist for more than a year with complaints of periodic polyarthralgia.