Overview
Influenza is an infectious disease caused by influenza viruses. It spreads from person to person and often appears in seasonal outbreaks, though timing varies by region. Many people recover within days to two weeks, but some develop complications such as pneumonia or worsening of other health problems.
Key Symptoms
Flu symptoms often begin suddenly. Common symptoms include fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache, and strong tiredness. Some people, especially children, may also have vomiting or diarrhea.
Causes and Risk Factors
Influenza is caused by influenza viruses, mainly influenza A and B. The virus spreads through respiratory droplets and can also spread through close contact with infected people or contaminated surfaces followed by touching the face. Risk of infection can increase in crowded settings, during seasonal outbreaks, and when a person has not received the current flu vaccine.
Who Is Affected
Anyone can get influenza, including healthy children and adults. Severe illness is more likely in older adults, very young children, pregnant people, and people with chronic conditions such as heart disease, lung disease, diabetes, or weakened immune systems. People living in care facilities or crowded homes may also be more exposed.
Prevention
Annual flu vaccination is one of the main ways to reduce the risk of infection and serious illness. Other helpful steps include washing hands, improving ventilation, covering coughs and sneezes, staying away from others when sick, and wearing a mask in high-risk situations or when advised by local public health authorities. Avoid close contact with people who are ill when possible.
Diagnosis and Tests
A healthcare professional may suspect influenza based on symptoms, local flu activity, and a physical examination. In some cases, testing of a nose or throat sample is used to confirm influenza, especially when results may affect care or infection control. Testing may be more important for people at higher risk of complications or those who are very unwell.
Treatment Categories
Treatment may include rest, fluids, and measures to relieve symptoms. Some people may be offered antiviral medicines by a healthcare professional, especially if they are at higher risk for severe illness or are seen early in the illness. Antibiotics do not treat influenza itself, though they may be used if a bacterial infection develops.
When to Seek Medical Care
Contact a healthcare professional if flu symptoms are severe, not improving, or if the sick person is in a higher-risk group such as an infant, older adult, pregnant person, or someone with chronic illness. Seek medical advice if there are signs of dehydration, trouble keeping fluids down, worsening cough, or symptoms that return after seeming to improve. Follow local public health advice during outbreaks.
When It May Be an Emergency
Emergency care may be needed for trouble breathing, chest pain, blue lips or face, confusion, seizures, severe weakness, or signs of dehydration such as very little urine or inability to drink. In children, warning signs can include fast breathing, difficulty waking, or a child who is not interacting normally. If someone seems dangerously ill, seek urgent medical help right away.