Influenza (flu)

Synonyms

Also Known as the Flu, Seasonal Influenza

Overview

Influenza, commonly known as the flu, is a contagious viral infection caused by influenza viruses. It primarily affects the respiratory system, including the nose, throat, bronchi, and lungs.The virus spreads through respiratory droplets when an infected person coughs or sneezes, with close contact being a major route of transmission.Flu symptoms include high fever, body aches, headache, dry cough, sore throat, and runny nose. These symptoms can overlap with those of the common cold and COVID-19.While many people recover within a few days, the flu can be severe and lead to complications, particularly in high-risk groups such as pregnant women, the elderly, young children, and those with chronic health conditions like asthma, and heart or kidney diseases.Treatment typically focuses on symptom relief, with antiviral medications prescribed for high-risk individuals in some cases.An annual flu vaccine is the most effective form of prevention, reducing the likelihood of contracting the flu, the severity of symptoms, and the risk of complications, especially for vulnerable populations.

Key Facts

Loading keyFacts...

Symptoms

Each person may experience symptoms differently. Although influenza is a respiratory disease, it can affect the whole body. Flu symptoms tend to come on suddenly and are generally more intense, including most or all of the following:

  • Cough that becomes severe gradually
  • Extreme exhaustion or tiredness
  • Severe muscle aches and pains
  • Runny or stuffy nose
  • Occasional sneezing
  • Sore throat
  • Tiredness for several weeks
  • Headache
  • Loss of appetite
  • High fever with chills
  • Vomiting and diarrhea (more common in children)
  • Pale face with watery and red eyes

Similarities and Differences Between Influenza and the Common Cold

Influenza (the flu) and the common cold are both contagious respiratory illnesses, but different viruses cause them. While they share some similarities, there are key differences that help distinguish them. Here’s a breakdown:

Symptoms

  • Similarity: Both conditions can cause a runny nose, headache, fatigue, and difficulty breathing.
  • Difference: Cold symptoms are usually milder, while flu symptoms are more severe and can lead to serious health issues like pneumonia.

Cause

  • Similarity: Both are caused by viruses.
  • Difference: Flu is caused exclusively by influenza viruses, while the common cold can be triggered by various viruses such as rhinoviruses, parainfluenza, and seasonal coronaviruses.

Incubation Period

  • Similarity: Both illnesses are highly contagious, with an incubation period of at least 1 day before symptoms appear.
  • Difference: Flu has an incubation period of 1-4 days, whereas a cold can take 1-7 days to show symptoms.

Duration of Illness

  • Similarity: Both flu and cold can last from a few days to two weeks.
  • Difference: A cold usually lasts 7-10 days, but can extend up to two weeks. Flu typically lasts 5 days to two weeks, depending on the severity.

Risk Factors

  • Similarity: Both illnesses pose higher risks for children, the elderly, pregnant women, and immunocompromised individuals.
  • Difference: The flu is more preventable through vaccination, while no vaccine exists for the common cold, making flu vaccination a key preventive measure.

Read more about how to know when your cold is more than a cold. Click Now

Similarities and Differences Between Influenza (Flu) and COVID-19

Influenza (flu) and COVID-19 are both contagious respiratory infections that affect the respiratory system, but different viruses cause them. COVID-19 is caused by the coronavirus, first identified in 2019, while the flu is caused by influenza viruses. Despite their similarities, these two infections have distinct characteristics. Here are some key similarities and differences:

Duration of Illness

  • Similarity: Both conditions take 1 or more days after exposure for symptoms to appear.
  • Difference: COVID-19 symptoms may take longer to appear, while flu symptoms typically develop within 1-4 days.

Duration of Virus Spread

  • Similarity: Both viruses can be transmitted at least 1 day before symptoms appear.
  • Difference: People infected with COVID-19 may remain contagious for a longer period (up to 7 days or more) compared to those with the flu.

Mode of Spread

  • Similarity: Both viruses spread through respiratory droplets when infected individuals cough, sneeze, or talk, typically within close contact (about 6 feet).
  • Difference: Although both viruses spread similarly, COVID-19 tends to be more contagious than the flu.

Individuals at Risk

  • Similarity: Older adults, individuals with underlying health conditions, and pregnant women are at higher risk of severe illness from both COVID-19 and the flu.
  • Difference: COVID-19 may cause more severe illness, resulting in hospitalization or death even in previously healthy individuals.

Complications

  • Similarity: Both infections can lead to respiratory complications.
  • Difference: While most flu patients recover within a few days to two weeks, COVID-19 can lead to ongoing complications even after recovery, including "long COVID" symptoms.

These similarities and differences are important for distinguishing between the two infections, though testing is necessary for an accurate diagnosis. COVID-19 is here to stay, but we need to adapt to it and get accustomed to the “new normal.”

FAQs on COVID-19

Cause

Influenza viruses cause seasonal influenza, primarily types A and B. These viruses undergo small genetic changes that lead to new strains each year.

The flu spreads primarily through respiratory droplets when an infected person coughs, sneezes, or talks. It can also spread through contact with contaminated surfaces.

The virus thrives in colder, drier conditions, which is why flu season typically occurs during the autumn and winter seasons.

RiskFactors

Several factors can increase the risk of contracting influenza or experiencing more severe complications. These include:

  • Age: Young children, especially those under 5, and adults over 65 are at higher risk.
  • Chronic health conditions: People with asthma, heart disease, kidney disease, diabetes, or other chronic conditions are more susceptible.
  • Pregnancy: Pregnant women, particularly in the second and third trimesters up to 2 weeks postpartum, are at greater risk for complications.
  • Weakened immune system: Individuals with weakened immune systems, such as those undergoing chemotherapy or living with HIV/AIDS, are more vulnerable.
  • Obesity: Severe obesity (BMI ≥ 40) increases the risk of flu-related complications.
  • Living or working in close quarters: Individuals in crowded environments like nursing homes, schools, or healthcare settings are more likely to be exposed.

These factors make certain groups more prone to severe flu infections or complications.

Have concerns about the flu and your risk? Get expert advice from our trusted team of doctors who can provide personalized guidance and help you stay informed and protected. Consult Now.

Diagnosis

Influenza testing is not mandatory for outpatients with suspected flu, particularly when seasonal influenza is circulating in the community. However, testing is recommended for certain cases, such as hospitalized patients or those requiring critical care, to guide treatment and prevent transmission.

Here are the main types of diagnostic tests used:

  • Rapid Influenza Diagnostic Tests (RIDTs)
    These tests detect influenza viral antigens in respiratory samples (usually from a nasal or throat swab).
    Pros: Provide quick results, often within 15-30 minutes.
    Cons: Less accurate than other tests, with a higher chance of false-negative results, especially in individuals with low viral loads.
  • Reverse Transcription-Polymerase Chain Reaction (RT-PCR)
    This highly sensitive test detects the genetic material (RNA) of the influenza virus in respiratory samples.
    Pros: Highly accurate and considered the gold standard for influenza diagnosis.
    Cons: Takes longer (several hours to a day) for results and requires specialized laboratory equipment.
  • Immunofluorescence Assays (IFA)
    This test uses antibodies to detect influenza viruses in respiratory samples, producing results within a few hours.
    Pros: More accurate than RIDTs.
    Cons: Requires skilled laboratory personnel and may be less widely available than RIDTs.
  • Viral Culture
    This method involves growing the virus from respiratory samples in a laboratory to identify the virus.
    Pros: Helps identify the specific strain of influenza.
    Cons: Takes several days to produce results and is generally used in specialized labs for research or epidemiological surveillance.
  • Direct Fluorescent Antibody (DFA) Test
    Uses fluorescently labelled antibodies to detect the influenza virus in respiratory samples.
    Pros: More accurate than RIDTs and can differentiate between influenza A and B strains.
    Cons: Requires trained laboratory personnel and specific equipment, making it less widely available.

Each test has its advantages and limitations, and the choice of test depends on factors such as the timing of the test, available resources, and the patient's clinical presentation. Ensure accurate diagnosis with Tata 1mg from the safety and comfort of your home. Book Your Test Now.

Prevention

Influenza is commonly seen during seasonal changes and affects almost all age groups. It can be prevented to a certain extent through the following:

Flu Vaccination

The best way to prevent seasonal influenza is to receive a flu vaccination every year. Everyone above 6 months of age, including adults and children, should get vaccinated. However, the Ministry of Health and Family Welfare, India has prioritized the flu vaccination for the following high-risk groups:

  • Elderly individuals (≥65 years of age)
  • Children (aged 6 months to 8 years)
  • Pregnant women
  • Health care workers
  • People with chronic health conditions like asthma, diabetes, cancer, heart, liver, kidney, or blood disorders
  • Those who are immunocompromised

Note: The flu viruses are a constantly evolving entity, changing their form frequently. This means that last year's flu vaccine might not protect you from this year's new strains. Hence, the flu vaccine is redesigned to keep up. The most recent circulating viruses are identified and included in a new formula to offer the best yearly protection. The flu vaccine is a safe, effective, and cost-efficient way to protect yourself from severe flu, reduce hospitalizations, and prevent fatal outcomes. Do Not Delay! Book Your Flu Vaccine Today.

Other Important Measures

Apart from vaccination, prevention of influenza involves the following key strategies:

  • Good hygiene practices: Regularly wash hands with soap and water or use hand sanitizers to reduce the spread of the virus. Avoid touching the face, especially the eyes, nose, and mouth.
  • Respiratory etiquette: Cover your mouth and nose with a tissue or elbow when coughing or sneezing to prevent airborne transmission.
  • Avoid close contact: Stay away from individuals who are sick and practice social distancing, particularly during flu season.
  • Disinfection: Clean frequently touched surfaces, such as doorknobs and phones, to minimize the risk of spreading the virus.
  • Healthy lifestyle: Maintaining a healthy lifestyle with adequate sleep, nutrition, and regular exercise can help boost the immune system and reduce susceptibility to infection.

Treatment

The treatment of influenza focuses on relieving symptoms and, in some cases, using antiviral medications. Key treatment options include:

  1. Symptomatic relief
    • Pain relief medications: Over-the-counter (OTC) medications like paracetamol can help reduce fever, body aches, and headaches.
    • Cough suppressants: OTC medications like dextromethorphan can help alleviate coughing.
    • Hydration: Drink plenty of fluids to stay hydrated, especially if experiencing fever or dehydration.

    Important Note: Aspirin is strictly contraindicated in influenza due to its potential to cause Reye's syndrome, a rare but serious condition that leads to brain swelling and liver damage.

  2. Antiviral medications

    Oseltamivir phosphate (Tamiflu), Zanamivir (Relenza), and other antivirals can help shorten the duration and intensity of flu symptoms. These medications are especially important for high-risk individuals (e.g., the elderly and those with chronic illnesses).

  3. Hospitalization

    In severe cases, particularly for high-risk individuals, hospitalization may be necessary for supportive care, oxygen therapy, or intensive treatment.

HomeCare

Home care for the flu focuses on relieving symptoms and supporting the body’s recovery. Here are some key home care tips:

  1. Rest: Get plenty of rest to help your body recover and regain energy.
  2. Stay hydrated: Drink plenty of fluids like water, herbal teas, clear soups, coconut water, or electrolyte drinks to prevent dehydration and help ease congestion.
  3. Soothing remedies:
    • Use a humidifier or vaporizer to ease congestion and soothe your throat.
    • Gargle with warm salt water to alleviate a sore throat.
    • Drink warm fluids like tea or honey with lemon to soothe your throat.
  4. Diet and nutrition:
    • Eat light, nutritious meals if you have an appetite. Focus on fruits, vegetables, and broth-based soups.
    • Avoid certain food items in case of diarrhea and vomiting. These include caffeine, meats, spicy, fried, and fatty foods.
  5. Stay isolated: Stay home to rest and prevent spreading the flu to others. Avoid close contact with others, especially those at higher risk for complications.
  6. Monitor symptoms: Keep an eye on symptoms. Seek medical attention if you have difficulty breathing, chest pain, persistent high fever, or worsening symptoms.

These home care practices help support recovery, but if symptoms worsen or if you're in a high-risk group, it is important to consult a doctor.

Complications

Complications of seasonal influenza can range from mild to severe, particularly in high-risk groups such as young children, the elderly, pregnant women, and individuals with chronic health conditions. Common complications in adults include:

  • Pneumonia: Influenza can lead to bacterial or viral pneumonia, a severe lung infection that can cause difficulty breathing, chest pain, and fever.
  • Bronchitis: Influenza can cause inflammation of the bronchial tubes, leading to coughing, wheezing, and difficulty breathing.
  • Sinusitis and ear infections: Influenza can lead to bacterial infections in the sinuses or ears, causing pain, swelling, and discomfort.
  • Dehydration: High fever, vomiting, and diarrhea (more common in children) can lead to dehydration if fluids are not replenished adequately.
  • Exacerbation of chronic conditions: Flu can worsen existing conditions such as asthma and heart diseases, making management more difficult.
  • Sepsis: A severe, life-threatening response to infection that can result in widespread inflammation, organ failure, and even death.
  • Myocarditis and pericarditis: Inflammation of the heart muscle, which can lead to irregular heart rhythms and heart failure in severe cases.
  • Secondary infections: Due to a weakened immune system, flu can make individuals more vulnerable to other infections like bacterial infections.

Children and infants can experience the above-mentioned complications, along with some specific to their age group:

  • Croup: Causes a barking cough and breathing difficulties, worsening at night.
  • Febrile seizures: Caused by high fever, typically in children under 5, but generally short-lived.
  • Bronchiolitis: Inflammation of the small airways, causing wheezing and difficulty breathing, especially in infants.

References

Centers for Disease Control and Prevention
Influenza (Flu)
Aug 2020
World Health Organization
Influenza (seasonal)
Nov 2018
National Foundation for Infectious Diseases
Flu (Influenza)
Jan 2022
World Health Organization
2020
Chen L, Yuan X, Wang X, Wang Y, Du J, Tang Y, et al.
J Med Virol
2020
National Centre for Disease Control (NCDC)
NCDC, Ministry of Health & Family Welfare, Government of India
2024
Ministry of Health & Family Welfare (MoHFW)
Government of India
2024

Frequently asked questions

Influenza typically lasts about 1 to 2 weeks, with variations in severity and length based on individual health.
Flu vaccines are safe, having undergone rigorous testing and continuous monitoring. Most side effects are mild, while serious side effects are rare. Consult your doctor if you have concerns.
Everyone aged 6 months and older should receive the flu vaccine, particularly those at higher risk such as young children, pregnant women, the elderly, and individuals with chronic conditions.
The flu vaccine is updated annually to protect against evolving strains of the virus, ensuring optimal protection each year.
It is recommended to get vaccinated at least 2 weeks before flu season, ideally in early autumn, but vaccination is beneficial at any time during the season.