Influenza-like illness
Influenza-like illness (ILI), also known as flu-like syndrome or flu-like symptoms, is a medical diagnosis of possible influenza or other illness causing a set of common symptoms. These include fever, shivering, chills, malaise, dry cough, loss of appetite, body aches, nausea, and sneezing typically in connection with a sudden onset of illness.[1] In most cases, the symptoms are caused by cytokines released by immune system activation, and are thus relatively non-specific.
Common causes of ILI include the common cold and influenza, which tends to be less common but more severe than the common cold. Less common causes include side effects of many drugs and manifestations of many other diseases.
Definition[edit]
The term ILI can be used casually, but when used in the surveillance of influenza cases, can have a strict definition. The World Health Organization defines an illness as an ILI if the patient has a fever greater than or equal to 38 °C and a cough, which began in the last 10 days. If the patient requires hospitalisation, the illness is classified instead as a severe acute respiratory infection (SARI).[2] Other organisations may have different definitions. For instance, the CDC defines it as a 100 °F (38 °C) fever or greater, and a cough or sore throat.[3]
In horses[edit]
ILI occurs in some horses after intramuscular injection of vaccines. For these horses, light exercise speeds resolution of the ILI. Non-steroidal anti-inflammatory drugs (NSAIDs) may be given with the vaccine.[21]