Diarrhea is a Symptom of Influenza H1N1

Yes, diarrhea is a recognized symptom of Influenza H1N1, particularly more common in children than in adults with this infection. 1, 2

Gastrointestinal Symptoms in H1N1 Influenza

Gastrointestinal symptoms, including diarrhea, vomiting, and abdominal pain, are present in a relatively large proportion of both adult and pediatric cases of H1N1 influenza, in contrast to the relatively low incidence of gastrointestinal symptoms in seasonal influenza 1
Studies have shown that diarrhea occurs in approximately 28% of children and 16-40% of adults with confirmed H1N1 infection 3, 4
A meta-analysis found that the pooled prevalence of any digestive symptoms ranged from 30.9% for A(H1N1)pdm09 to 2.8% for seasonal A(H1N1) 5

Infants and very young children (under two years) with H1N1 are more likely than older children to present with gastrointestinal symptoms such as diarrhea and vomiting 1
In the 2009 H1N1 pandemic, 28% of pediatric patients presented with vomiting and 16% with diarrhea 4
During the first recorded instance of human infection by avian influenza H5N1 in Hong Kong (1997), abdominal symptoms including diarrhea were described in 56% of patients 1

The most common presenting features of H1N1 influenza include fever (present in nearly 100% of cases), cough, and rhinorrhea 1, 2
Other frequent symptoms include headache, sore throat, malaise, myalgia, and respiratory distress 2, 6

Neonates may present with non-specific signs of sepsis such as pallor, floppiness, lethargy, poor feeding, episodes of apnea, with fever sometimes being the only presenting feature 1, 2
Children typically present with sudden onset of high fever, chills, cough, headache, sore throat, and may have gastrointestinal symptoms 2
Adults commonly experience abrupt onset of constitutional and respiratory symptoms, with gastrointestinal symptoms being less common than in children 2

The presence of influenza viral RNA in stools suggests that the virus may localize in the gastrointestinal tract, particularly in children 7, 5
Viable influenza virus has been isolated from stool specimens, suggesting potential for intestinal infection 7
The mechanism may involve hematogenous dissemination to organs via infected lymphocytes 5

The presence of diarrhea in patients with influenza-like illness should raise suspicion for H1N1 infection, especially in children 2, 3
Gastrointestinal symptoms may contribute to dehydration and electrolyte imbalances, which can be severe complications of H1N1 infection 6, 4
One case report noted a child with H1N1 presenting with hypernatremic dehydration and seizures, highlighting the potential severity of gastrointestinal involvement 4

Diarrhea as a symptom of H1N1 may lead to misdiagnosis as a primary gastrointestinal illness rather than influenza 7, 5
The detection of influenza virus in stool raises concerns about potential fecal-oral transmission during seasonal and epidemic influenza outbreaks 7
Patients with gastrointestinal symptoms may require additional supportive care for hydration and electrolyte management 6, 4
When evaluating patients with influenza-like illness, clinicians should inquire about gastrointestinal symptoms, particularly in children, as these may be part of the clinical presentation of H1N1 infection 2, 3