Table 6.

Considerations for Future Birth Cohort Studies

Methodological • Use real-time RT-PCR detection assays for norovirus screening  o Report Ct values for relative quantification of viral load and establish Ct cutoff values for real-time amplification • Perform conventional RT-PCR and genotyping and/or next-generation sequencing on real-time positive results  o Sequence regions of the capsid for genotyping and polymerase for dual-typing; amplify longer regions of the capsid and/or genome when possible • When screening for coinfections/other enteropathogens, use sensitive methods targeting a broad panel of viral, bacterial, and parasitic pathogens for better resolution of disease attribution • Implement quality assurance and quality control parameters for detection assays and laboratorians (ie, standard operating procedures, proficiency panels, internal controls) • Defining illness: Use ≥3 stools within 24 hours for diarrheal illness • Define events of vomiting-only gastroenteritis and mixed (diarrhea and vomiting) gastroenteritis • Routine stool collection: as frequent as practical for increased resolution of “asymptomatic” vs “long-term shedding” • To better capture episodes of diarrhea, visit enrolled participant homes as frequently as possible rather than relying on them to contact study or clinic personnel

Reporting for incidence, prevalence, and disease attribution • Incidence of infections • Prevalence in asymptomatic and diarrheal stools • Incidence of norovirus-associated diarrhea • Disease attribution estimates • Include values for each community/country studied if multiple locations are included in the study

Immunity and molecular epidemiology • Examine genogroup-specific protection following prior infection/illness • Examine genotype-specific protection following prior infection/illness • Determine if >1 infection/illness confers a higher degree of protection • Further study reinfections by same genotype or GII.4 variant (sequencing longer genome regions, determine immunostatus of patients) • Include a timeline of infections for each child to better assess community exposures • Further assess community exposures by testing specimens from other household (such as siblings) or community members

Collect data for disease determinants • Child age with each infection/illness • Severity of illness • Virus (genotype)–specific disease determinants • Coinfections with other enteropathogens • Genetic predisposition (HBGA phenotypes, genotypes) • Nutritional and lifestyle factors (height/weight, exclusive breastfeeding, socioeconomic status, mother’s education, access to clean water and basic sanitation, etc) • Risk factors for pregnant and nursing mothers • Microbiome: comparison between infected and uninfected populations, between different communities, and changes in microbiome that occur with age, breastfeeding status, and with infection(s) • Collect convalescent sera (sera collection 2 weeks after diarrheal event or infection) after repeat infections and perform HBGA blockade or in vitro neutralization

Abbreviations: Ct, cycle threshold; GII, genogroup II; HBGA, histo-blood group antigen; RT-PCR, reverse-transcription polymerase chain reaction.