Fecal detection of influenza A virus in patients with concurrent respiratory and gastrointestinal symptoms

Abstract

Background: In seasonal influenza, gastrointestinal symptoms such as diarrhea, vomiting, and abdominal pain are sometimes observed, especially among young children. However, fecal excretion of seasonal influenza virus has seldom been studied.

Objective: To investigate the presence of human influenza A virus in stool specimens of patients presented with symptoms of gastroenteritis.

Study design: A retrospective study on 651 stool specimens collected from 627 patients of all age groups presented with symptoms of gastroenteritis during a 12-month period (December 2004-November 2005). Influenza A viral RNA was detected by conventional polymerase chain reaction (PCR) targeting the matrix gene. Virus subtyping was performed by multiplexed H1- and H3-specific PCR. Fecal viral concentration was estimated by TaqMan-based real-time PCR. Clinical records of positive cases were reviewed.

Results: Seasonal influenza A (H3N2) viral RNA was detected in 7 stool specimens collected from 6 patients. Their time of presentation coincided with local influenza season. All patients were at the extreme of ages (<5 or >60 years) or had underlying comorbidities, and had concurrent respiratory and gastrointestinal symptoms. All required hospitalization and 1 patient died. Two patients with underlying lymphoma had the highest viral concentrations in their stool specimens.

Conclusions: Influenza A viral RNA can be detected in stool specimens of 6 high-risk influenza patients with concurrent respiratory and gastrointestinal symptoms. Further investigation on the gastrointestinal involvement of seasonal influenza is required.