Flu is a respiratory illness, and most people identify it through symptoms like sore throat, runny nose, cough, fatigue, and fever. However, it can sometimes affect the gastrointestinal tract and lead to digestive discomfort. Diarrhoea may be an unusual sign of flu, which can often be confused with other digestive conditions.
Therefore, in an interaction with the OnlyMyHealth team, Dr Srinivasa Chary A, Consultant General Medicine, Gleneagles Aware Hospital, LB Nagar, Hyderabad, explains why and how flu causes diarrhoea, how it can be differentiated with other digestive issues, and what can be done to manage the same.
Also Read: IBS Can Cause Both Constipation And Diarrhoea: Expert Explains Why This Happens And How To Manage It
Diarrhoea - A Less Common Sign Of Flu
Dr Srinivasa says that diarrhoea is a less common symptom of flu compared to respiratory symptoms like fever, cough, and body aches.
According to him, it can occur, especially in children, older adults, and those with weakened immune systems. The influenza virus can affect the gastrointestinal tract, leading to nausea, vomiting, and diarrhoea in some cases.
While the flu virus enters through the respiratory route, it can spread to the gastrointestinal tract and cause a secondary infection.
Although it is unknown how flu virus travels to gastrointestinal tract, a 2015 study published in Virology Journal shares a few possibilities:
- Swallowing infected mucus
- Infected immune cells carrying the virus to the gut
- The virus is potentially multiplying in the gut.
- Flu possibly making gut bacteria stickier, causing stomach problems
How To Differentiate Flu-Related Diarrhoea With
![2]()
Digestive Issues
Digestive IssuesFlu-related diarrhoea is usually accompanied by classic flu symptoms such as fever, fatigue, muscle aches, and respiratory issues.
In contrast, bacterial or viral gastrointestinal infections (like norovirus) typically cause isolated digestive symptoms like severe vomiting, cramping, and persistent diarrhoea without respiratory involvement.
Also Read: Is Now A Good Time To Get Your Flu Shot? Who Should Consider It
How To Manage Diarrhoea Caused By Flu
If you experience diarrhoea, regardless of its cause, Dr Srinivasa recommends drinking plenty of fluids with electrolytes to prevent dehydration. He further advises eating light, bland foods like bananas, rice, applesauce, and toast (BRAT diet) and avoiding caffeine, alcohol, and greasy foods.
As there isn’t a standard treatment for flu infections, rest is essential to aid recovery. However, if symptoms worsen, consult a doctor immediately. This is particularly important if you experience severe dehydration (dizziness, dry mouth, reduced urination), bloody stools, high fever, or persistent diarrhoea lasting more than 2-3 days.
High-risk groups, like infants, elderly individuals, and those with chronic illnesses, should seek prompt care.
Role Of Flu Vaccines
According to the US Centers for Disease Control and Prevention (CDC), everyone six months and older should get a flu vaccine every season with rare exceptions.
"Flu vaccines can reduce the severity and duration of flu-related symptoms, including gastrointestinal issues. While flu vaccines primarily protect against respiratory complications, they lower overall viral load, reducing the chances of flu-related diarrhoea," Dr Srinivasa highlights.