5. Gender based dimorphism in host response to viral infection: Two interesting epidemiological trends observed during Chikungunya outbreak in Kerala

Abstract

Introduction: Males and females respond differently to infection, which again is modified by the ‘stage of life cycle’ they belong to. This knowledge however is often neglected during surveys/ studies or while deliberating protocols for disease control. Materials and methods: Data collected without segregation of sexes in separate age groups may thus be biased, confounding conclusions and disease control strategies formulated based on them. We analyzed results of IgM ELISA tests for chikungunya virus (CHIKV) released by Kerala State Institute for Virology and Infectious Diseases (KSIVID) done in 2007 during last epidemic caused by the virus in Kerala, and found two interesting epidemiological trends relating to sex based dimorphism in host response to CHIKV. Results: The ‘proportion’ of seropositive females over males increased steadily from near puberty, to become one of clear female predominance in reproductory age group, and then waning through middle age, reverting to original proportions, by menopause. From a situation where IgM positive males and females about equally represented, during the early epidemic, the proportion of positive females increased through mid-epidemic period, almost 'eclipsing' the male segment and then waned during post-epidemic period, the ratio tending to revert to original proportions. Conclusions: We seek to emphasize the importance of collecting and analyzing data separately for males and females categorized in different stages of life cycle (as per guidelines of W.H.O.) in studies/ epidemiological surveys