Dynamics of asymptomatic Norovirus infections in a three-year cohort of children from rural communities in Ecuador.

Rommel Guevara, Universidad San Francisco de Quito

Rommel Guevara1, Lesly Simbaña Vivanco1, Stuart Torres Ayala1, Lorena Mejía1, Gabriel Trueba1, Joseph Eisenberg2, Karen Levy3, and Benjamin Arnold4 1. Instituto de Microbiología, Universidad San Francisco de Quito, Quito, Pichincha, Ecuador 2. Public Health Department, University of Michigan, Michigan, USA 3. Department of Environmental and Occupational Health Sciences, University of Washington School of Public Health, Seattle, Washington, USA 4. Institute for Global Health Sciences, University of California, San Francisco, California, USA

Molecular Epidemiology & Evolution

Norovirus, part of the Caliciviridae family, is one of the leading causes of gastrointestinal infections in humans worldwide. In adults, the infection is generally undiagnosed because it is usually self-resolved or even asymptomatic. However, chronic infections or recurrent reinfections may occur in more susceptible patients such as children or the elderly. In low- and middle-income countries, poor sanitation could lead to more frequent outbreaks and the emergence of virulent strains. This project aimed to elucidate the epidemiology of norovirus infection in children from rural communities in the Ecuadorian province of Esmeraldas. The children were followed for three years as part of the ECoMiD project, which studies the influence of enteropathogens on child development. 219 samples were positive for norovirus, all asymptomatic cases, 109 of them successfully typed as genogroups GI (38%) and GII (62%). Near-complete genomes and capsid-polymerase junction amplicons were used to genotype samples. Monthly frequency of cases showed four non-overlapping increases, two of GI one year apart and two of GII five months apart. Sequencing revealed different genotypes within each increase, suggesting that they were not common source outbreaks. Suspected reinfections were identified in twelve children, eight of them confirmed by sequencing: six between different genogroups and two within the same (GII). Different genotypes caused the GII reinfections at least six months after the first infection. The results of this work show a pattern of norovirus infection by different genogroups over time and suggest short-lived immune protection against reinfections, even those caused by closely related strains.