Persistence of anti-zika virus Immunoglobulin M antibodies in children with microcephaly up to four years after primary infection

Zika virus (ZIKV) is a member of the flaviviridae family of virus, considered to cause acute self-limited infection in adults, though it may lead to severe complications. It is believed that ZIKV infection elicit a classical viral immune reaction, with primary IgM antibody response and secondary IgG immunity. Persistence of IgM antibodies has been identified for other viruses belonging to the same family as ZIKV. We investigated, therefore, the presence of anti-ZIKV IgM antibodies in children with microcephaly born between January 2015 and November 2018, and their parents. We have detected persistence of IgM in 22% of children with microcephaly up to four years after primary infection. Long term IgM persistence have implications for the diagnosis of acute infection. More investigation is needed in order to correctly construe the significance of anti-ZIKV IgM persistence in the population in general, and in children with microcephaly in particular. The dynamics of IgM antibody responses against ZIKV must be known and understood to avoid misinterpretation of diagnosis for acute infection, re-infection and antibody persistence.