Laboratory confirmation of rubella infection in suspected measles cases

As a part of measles outbreak based surveillance undertaken by the World Health Organization India, suspected measles cases were referred for the laboratory diagnosis at National Institute of Virology (NIV) Pune and NIV Unit Bengaluru. Altogether, 4,592 serum samples were referred during 2010-2015 from the States of Karnataka (n = 1,173), Kerala (n = 559), and Maharashtra (n = 2,860). Initially, serum samples were tested in measles IgM antibody EIA and samples with measles negative and equivocal results (n = 1,954) were subjected to rubella IgM antibody detection. Overall, 62.9% (2,889/4,592) samples were laboratory confirmed measles, 27.7% (542/1,954) were laboratory confirmed rubella and remaining 25.2% (1,161/4,592) were negative for measles and rubella. The measles vaccination status was available for 1,206 cases. Among the vaccinated individuals, 50.7% (612/1,206) were laboratory confirmed measles. The contribution of laboratory confirmed measles was 493 (40.8%) from Maharashtra, 90 (7.5%) from Karnataka, and 29 (2.4%) from Kerala. Since, 1/3rd of suspected measles cases were laboratory confirmed rubella, an urgent attention needed to build rubella surveillance in India. Additional efforts are required to rule out other exanthematous disease including Dengue and Chikungunya in measles and rubella negatives. J. Med. Virol. 88:1685-1689, 2016. © 2016 Wiley Periodicals, Inc.