Primary care-based surveillance to estimate the proportion of rotavirus gastroenteritis among Latvian children below 5 years of age with acute gastroenteritis

Background: Rotavirus (RV) is worldwide an important cause of acute gastroenteritis (AGE) in infants and young children. There is no specific treatment for AGE caused by RV (RVGE) but since 2006 two safe and effective vaccines have been available. RV vaccination was included in the national immunization program (NIP) of Latvia in 2015 with full reimbursement, and within the first year a coverage of 87% was achieved. This surveillance study was carried out to investigate the proportion of RVGE among AGE episodes in Latvia up to the inclusion of RV vaccination in the NIP to provide a basis for future assessments of the impact of RV vaccination. Methods: Prospective, one-year observational study of children younger than 5 years presenting with AGE in the primary care setting. At first primary care contact, a stool sample was collected and tested for RV using a rapid, visual immunochromatographic kit. The parents monitored their child's symptoms over 2 weeks after the first contact and the investigator recorded these observations during a follow-up phone call. The proportion of RVGE among the AGE cases was estimated and the severity of each AGE case was assessed based on the recorded symptoms using the 20-point Vesikari scale. The seasonality of RVGE was also investigated. Results: Fifty-two primary care investigators collected data on 606 evaluable children with AGE. The proportion of RVGE was 38.1%. Severe AGE was experienced by 40.7% of the RV-positive and 19.5% of the RV-negative patients. The rate of hospitalization was 9.1% for the RV-positive and 4.8% for the RV-negative with no difference in the mean duration of hospital stays. AGE and RVGE both occurred all year round but with a clearly marked peak only for RVGE, from March to May. Conclusion: This study underlines that RV is an important cause of AGE in children under 5 years old in Latvia and that the burden of disease of RVGE in primary care was substantial before inclusion of RV vaccination in the NIP.