Respiratory Syncytial Virus Symptomatic Fraction, Shedding and Detection in Children Aged 6-23 Months in South Africa in 2022.

BACKGROUND

Accurate detection of RSV infections is important to understand epidemiology. We estimated symptomatic fraction and shedding duration of reverse-transcription polymerase chain reaction (RT-PCR)-confirmed cases and compared RSV detection through molecular and serologic techniques.

METHODS

We enrolled healthy children aged 6-23 months in a prospective cohort study, from May to October 2022, collecting thrice-weekly mid-turbinate nasal swabs for RSV RT-PCR testing. We collected serum at baseline and end of follow-up and detected anti-RSV IgG using enzyme-linked immunosorbent assay (ELISA) and multipathogen bead-based immunoassay (MIA). We ascertained symptoms by twice-weekly nurse visits, and daily caregiver symptom diaries. We calculated sensitivity, specificity, and positive (PPV) and negative (NPV) predictive value of RT-PCR, ELISA, and MIA compared to a standard (two or more assays-positive) among children with paired sera and baseline blood preceding an RT-PCR-confirmed episode.

RESULTS

The RSV season started mid-February 2022. We enrolled 93 participants; 87 (94%) followed to the final study visit. Forty individuals had one or more RT-PCR-confirmed RSV infection, and six of them had a repeat episode. One-or-more symptom was reported from 54% (25/46) of RT-PCR-confirmed episodes, fever in 26% (12/46), and cough in 37% (17/46). Median RNA shedding duration was 7 days (IQR = 4-11 days). Among 80 children meeting criteria, ELISA and MIA each had > 92% sensitivity, specificity, PPV, and NPV while RT-PCR had 78% (95% CI = 61%-90%) sensitivity, 98% (95% CI = 88-100%) specificity, 97% (95% CI = 82%-100%) PPV, and 84% (95% CI = 71%-93%) NPV.

DISCUSSION: Approximately half of RSV episodes were symptomatic. Serology had a high sensitivity and specificity for infection identification.