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.

Abbreviations: CXR, chest X-ray, GI, gastrointestinal, M gene, matrix gene, N/A, not available, ND, not done, NPA, nasopharyngeal aspirate, PCR, polymerase chain reaction, RNA, ribonucleic acid, URTI, upper respiratory tract infection

Keywords: Influenza A virus, Gastrointestinal symptoms, Stool, RNA