What are the symptoms of influenza (the flu)?

Influenza, commonly known as the flu, is an acute respiratory infection with a variety of symptoms ranging from mild to severe.

Fever and cough are the most frequently reported symptoms of influenza, with fever often being high and continuous, and cough typically being dry .
Systemic symptoms such as fatigue, body aches, and muscle pain are common, with some patients experiencing severe muscle pain .
Upper respiratory symptoms like sore throat, runny or stuffy nose, and lower respiratory symptoms can persist, with lower respiratory symptoms resolving more slowly .
Other symptoms may include headaches, chills, eye pain, and a general feeling of sickness.
Less commonly, influenza can present with gastrointestinal symptoms, particularly in children, and can lead to serious complications such as pneumonia or, in rare cases, rhabdomyolysis and acute respiratory failure .
The combination of fever with cough has been identified as a significant predictor for influenza infection, although the predictive value and sensitivity of these symptoms can be low in hospitalized patients .

In conclusion, influenza symptoms are diverse and can include fever, cough, fatigue, muscle pain, and various respiratory symptoms. While fever and cough are the most indicative of the flu, the presence of additional symptoms can vary, and the severity of the disease can lead to complications requiring medical attention.

What are the symptoms of influenza (the flu)?

Summary

Sources and full results

Dynamics of clinical symptoms in patients with pandemic influenza A (H1N1).

The 2009 pandemic influenza A (H1N1) virus primarily affects the lower respiratory tract and may be the main cause of pneumonia, with fever and cough being the most frequent symptoms.

Predicting influenza infections during epidemics with use of a clinical case definition.

A clinical case definition including fever (temperature of >38 degrees C) and cough effectively predicted influenza infections during the 1998-1999 flu season, with 86.8% positive predictive value, 39.3% negative predictive value, 77.6% sensitivity, and 55.0% specificity.

Influenza

Influenza is a highly contagious respiratory infection caused by influenza virus, with symptoms ranging from high fever, fatigue, and muscle soreness to mild respiratory tract symptoms.

Influenza fact sheet.

Flu symptoms include fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, and sometimes vomiting and diarrhea.

Fighting the Flu

Influenza symptoms include fever, chills, body aches, headache, fatigue, and loss of appetite.

Symptoms of Influenza Virus Infection in Hospitalized Patients

Fever, cough, and other symptoms have low sensitivity and positive predictive value for diagnosing influenza virus infection in hospitalized patients, making their use for treatment decisions and infection control management insufficient.

[Severe course of influenza B complicated by rhabdomyolysis and acute respiratory failure resulting in death].

Influenza B can cause severe muscle weakness and rhabdomyolysis, leading to acute respiratory failure and death in a 51-year-old male.

The common cold and influenza

The common cold is milder and more likely to cause a runny or stuffy nose, while the flu is more severe and has more common and intense symptoms.

Understanding the symptoms of the common cold and influenza

New knowledge of cytokines helps explain some previously folkloric symptoms of colds and flu, improving our understanding of their mechanisms.

Research and developments of vaccines and drug treatments for influenza

Influenza research focuses on developing vaccines and drug treatments to prevent and treat influenza, which can cause serious illness or death due to pneumonia and other life-threatening complications.

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