Which severe symptoms could occur during H1N1 infection?

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Caring for flu victims — influenza pandemic (H1N1) of 2009 Doctors at the Mexico City Navy Hospital wearing protective gear as they tend to patients complaining of H1N1 flu-like symptoms.

While most individuals infected with the 2009 H1N1 virus experienced mild respiratory symptoms and fever, some cases were severe. These severe symptoms included:

Diarrhea1
Chills1
Vomiting1
Respiratory failure (in rare cases)1

The virus was found to be most lethal in individuals who suffered from chronic diseases or other underlying health conditions.1