High Levels of Co-detection of Norovirus and Other Enteric Pathogens in Patients with and without Acute Gastroenteritis in a Hospital-Based Surveillance Study in Bangladesh, 2018-2021.

BACKGROUND

The contribution of various enteropathogens to the occurrence of acute gastroenteritis (AGE) remains uncertain in highly endemic settings. We describe the frequency of norovirus-only detections and norovirus co-detections in hospitalized patients in Bangladesh and compare their clinical severity and viral load.

METHODS

From March 2018-October 2021, 1,250 AGE cases and 1,250 non-AGE controls of all ages were enrolled at 10 tertiary care hospitals in Bangladesh. All norovirus-positive AGE cases (n=111) and non-AGE controls (n=182), and a randomly selected subset of 126 norovirus-negative AGE cases, were tested for other enteric viral, bacterial, and parasitic co-pathogens with quantitative real-time PCR assays. We used cycle threshold (Ct)-values as a proxy for viral load and Vesikari scale to assess disease severity.

RESULTS

Among 111 norovirus-positive AGE cases, 29 (26%) were norovirus-only detections and 82 (74%) were norovirus co-detections, and among 182 norovirus-positive non-AGE controls, 59 (32%) were norovirus-only detections and 123 (68%) were norovirus co-detections. Norovirus-rotavirus was the predominant co-detection, found in 140 (68%) of 205 norovirus co-detections. No differences in clinical severity were observed among AGE cases with norovirus-only versus norovirus co-detections. The median (interquartile range) Ct-values among genogroup II norovirus-only AGE cases, norovirus co-detection AGE cases, and norovirus-positive non-AGE controls were 25 (22-30), 25 (21-30), and 26 (21-30), respectively.

CONCLUSIONS

The frequent co-detection of norovirus with other enteropathogens, especially rotavirus, along with overlapping Ct-values in patients with and without AGE, and between norovirus-only and norovirus co-detections, complicates the attribution of norovirus as a cause of AGE in Bangladesh.