Influenza

Overview

Influenza, often called the flu, is a contagious respiratory infection caused by influenza viruses. It mainly affects the nose, throat, and lungs. Influenza can occur at any time, but it is more common during seasonal outbreaks, especially in colder months in many regions.

For many people, influenza causes a short-term illness that improves with rest and supportive care. However, it can sometimes lead to complications, particularly in young children, older adults, pregnant people, and individuals with certain long-term health conditions. Because influenza spreads easily from person to person, prevention and early medical advice are important, especially for people at higher risk.

Symptoms

Influenza symptoms often begin suddenly. They can range from mild to severe and may be different from person to person. Common symptoms include:

• Fever or feeling feverish with chills
• Cough, which may be dry or persistent
• Sore throat
• Runny or blocked nose
• Muscle aches or body aches
• Headache
• Tiredness or weakness
• Loss of appetite
• Sometimes nausea, vomiting, or diarrhea, more often in children

Influenza is different from the common cold because symptoms usually start more suddenly and tend to be more intense. A person with influenza may feel too unwell to continue normal daily activities. Most symptoms improve gradually, but cough and tiredness can last longer than the initial fever and aches.

Causes and Risk Factors

Influenza is caused by influenza viruses that spread through droplets when an infected person coughs, sneezes, or talks. The virus can also spread by touching contaminated surfaces and then touching the mouth, nose, or eyes. People may pass the virus to others before they realize they are sick and during the first days of illness.

Certain factors may increase the risk of catching influenza or developing more serious illness. These include:

• Close contact with someone who has influenza
• Being in crowded places, such as schools, public transport, or shared workplaces
• Young age, especially infants and young children
• Older age
• Pregnancy or the period shortly after giving birth
• Chronic medical conditions affecting the lungs, heart, kidneys, liver, blood, or immune system
• Living in long-term care or residential facilities
• Weakened immune defenses due to illness or medical treatment

Annual vaccination is one of the key measures used to reduce the risk of influenza and its complications. Good hand hygiene, covering coughs and sneezes, staying home when ill, and avoiding close contact with sick people can also help reduce spread.

Diagnosis

Doctors often suspect influenza based on symptoms, physical examination, and whether influenza is circulating in the community. During the medical visit, the doctor may ask about the timing of symptoms, exposure to sick contacts, travel, vaccination history, and any underlying health conditions.

In some cases, testing may be recommended. A sample is usually collected from the nose or throat to check for influenza virus. Testing may be more important for people at higher risk of complications, those who are very unwell, hospitalized patients, or when the result may affect treatment decisions or infection control measures.

Because influenza symptoms can resemble other respiratory infections, including other viral illnesses, medical evaluation helps distinguish between possible causes and identify warning signs of complications.

Treatment Options

Treatment depends on the person’s age, overall health, symptom severity, and risk of complications. Many people with uncomplicated influenza recover with supportive care. This may include resting, drinking enough fluids, and following a healthcare professional’s advice for comfort and fever management.

For some patients, especially those at higher risk or those seen early in the illness, a doctor may consider prescription antiviral treatment. The decision depends on clinical assessment and timing. These medicines are not suitable for everyone, and they should only be used under medical guidance.

Antibiotics do not treat influenza itself because influenza is caused by a virus. However, a doctor may evaluate for bacterial complications if symptoms worsen, persist, or suggest another infection. Possible complications of influenza include pneumonia, worsening of asthma or chronic lung disease, ear infections in children, dehydration, and worsening of existing heart or other medical conditions.

People with influenza should also take steps to avoid spreading the virus. This includes staying away from others while contagious, covering coughs and sneezes, washing hands regularly, and wearing a mask when advised or when close contact cannot be avoided.

When to See a Doctor

Medical advice is recommended if influenza symptoms are severe, worsening, or occur in someone at higher risk of complications. Seek prompt medical attention for:

• Difficulty breathing or shortness of breath
• Chest pain or pressure
• Confusion, extreme drowsiness, or fainting
• Blue or pale lips or face
• Severe weakness or inability to stay hydrated
• Fever that improves and then returns with worsening cough or symptoms
• Symptoms in infants, older adults, pregnant people, or people with chronic medical conditions
• Signs of dehydration, such as very little urination, dizziness, or inability to keep fluids down

Parents should seek medical care urgently if a child has breathing difficulty, persistent high fever, severe sleepiness, irritability, signs of dehydration, or symptoms that improve and then suddenly become worse.

Influenza is common, but it should not be ignored in people who are vulnerable or very unwell. Early guidance from a healthcare professional can help ensure appropriate care and reduce the risk of complications.