General Health

Influenza: Symptoms, Causes, Treatment, Prevention

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By Apollo 24|7, Published on- 03 August 2023, Updated on - 08 August 2023

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Influenza, commonly known as the flu, is a viral infection that affects millions of people worldwide. In India, influenza is a significant health concern, with outbreaks occurring annually. Influenza can lead to severe illness and even death, especially in vulnerable populations such as the elderly, young children, pregnant women and those with underlying health conditions. India experiences a high burden of influenza-associated illness and mortality each year. By knowing about influenza, we can take appropriate preventive measures, get vaccinated and seek timely medical care when needed.

Types and Strains of Influenza

Influenza is a respiratory disease caused by different types and strains of viruses. The two main types are influenza A and influenza B.

1. Seasonal Influenza

Seasonal influenza refers to the flu that occurs every year, with common strains being H1N1, H3N2 and influenza B. These strains can vary in severity and can cause mild to severe illness. The impact of seasonal influenza on public health should not be underestimated as it can lead to hospitalisations, complications and even death.

2. Pandemic Influenza

Pandemic influenza is a global outbreak of a new strain of the influenza virus that spreads easily from person to person. Unlike seasonal flu, which is caused by known strains, pandemic flu arises from a novel strain that humans have little to no immunity against. Examples of past pandemics include the Spanish flu in 1918, the Asian flu in 1957 and the H1N1 pandemic in 2009.

By being aware of these variations, we can better prepare for flu seasons, take necessary precautions to prevent infection, and ensure appropriate measures are in place to mitigate the impact of future pandemics.

Causes and Transmission of Influenza

Understanding the causes and modes of transmission of influenza is crucial to prevent its spread.

1. Influenza Virus Types

Influenza A, B and C viruses are the main types of influenza.

  • Influenza A virus is the most common and has different subtypes based on surface proteins.
  • Influenza B is less common and affects humans only.
  • Influenza C is rare and causes mild respiratory illness.

2. Modes of Transmission

Influenza is primarily transmitted through airborne respiratory droplets that are produced when an infected person coughs or sneezes. These droplets can be inhaled by others nearby. Furthermore, direct contact with contaminated surfaces, such as doorknobs or countertops, can also spread the virus.

Symptoms of Influenza

It is important to be aware of the influenza symptoms to seek timely medical attention and prevent further health complications. Some of the common influenza symptoms include:

  • Fever: One of the main signs of influenza is a sudden onset of high fever (above 100.4°F or 38°C).
  • Cough: A dry or productive cough is another common symptom that can persist for several weeks.
  • Sore Throat: Influenza can cause a scratchy or painful throat, making it difficult to swallow.
  • Body Aches: Severe body aches and muscle pain are often reported by individuals with influenza.
  • Fatigue and Weakness: Feeling exhausted and lacking energy is a typical symptom during the illness.

Complications of Influenza

While most cases of influenza resolve on their own, certain individuals are at higher risk of developing complications. These can include:

1. Pneumonia and Respiratory Infections

Influenza can weaken the immune system, making individuals more susceptible to secondary bacterial infections such as pneumonia or bronchitis. These complications can be severe, particularly in older adults, young children, pregnant women and those with weak immunity.

2. Worsening of Existing Medical Conditions

Individuals with underlying health conditions such as asthma, chronic obstructive pulmonary disease (COPD), diabetes, heart disease or weakened immune systems are more likely to experience exacerbation of these conditions when infected with influenza.

It is important to seek medical attention if you experience severe symptoms or if you have any underlying health conditions that could put you at a higher risk for complications.

Diagnosis of Influenza

There are several diagnostic methods available to detect flu, some of which include:

  • Rapid Influenza Diagnostic Tests (RIDTs): These tests provide quick results by detecting the presence of influenza viral antigens in respiratory specimens. They are commonly used in clinics and emergency departments.
  • Viral Culture and Polymerase Chain Reaction (PCR): These tests are more sensitive and specific than RIDTs, but they take longer to produce results. Influenza test by PCR can help identify the specific strain of influenza.

Treatment of Influenza

Antiviral medications play a crucial role in managing influenza by inhibiting the replication of the virus and reducing the severity and duration of symptoms. They are most effective when started within 48 hours of symptom onset.

It's important to note that antiviral medications are prescription-only, so it's essential to consult a healthcare professional for a proper diagnosis and prescription.

In addition to influenza medicine, supportive care measures can also provide symptom relief. These measures include:

  • Getting plenty of rest to help the body recover.
  • Staying hydrated by drinking fluids such as water, herbal teas and clear soups.
  • Taking over-the-counter pain relievers like acetaminophen or ibuprofen to alleviate fever, headache and body aches.
  • Using saline nasal sprays or saltwater gargles to relieve congestion and sore throat.
  • Avoiding close contact with others to prevent the spread of the virus.

Prevention of Influenza

There are several measures you can take to prevent the spread of influenza and reduce your risk of getting infected.

1. Vaccination

Getting a flu vaccine or flu shot each year is crucial in protecting yourself and those around you from the influenza virus. The influenza vaccine stimulates your immune system to produce antibodies that fight against specific strains of the virus. It reduces the severity of symptoms (if you get infected) and lowers the chances of complications or hospitalisation.

The flu vaccines available in India include both trivalent and quadrivalent vaccines. Trivalent vaccines protect against three strains of the flu virus, while quadrivalent vaccines protect against four strains. Talk to your healthcare provider to determine which vaccine is most suitable for you.

2. Hygiene Practices

Practising good hand hygiene is essential in preventing the spread of the flu virus. Some of the hygiene practices include:

  • Handwashing and Respiratory Hygiene Techniques: Proper hand hygiene is essential in preventing the spread of influenza. Wash your hands frequently with soap and water for at least 20 seconds, especially after coughing, sneezing or being in public places. If soap and water are not available, use an alcohol-based hand sanitiser.
  • Avoiding Close Contact with Infected Individuals: Influenza is primarily transmitted through respiratory droplets when an infected person coughs or sneezes. Avoid close contact with individuals who have flu-like symptoms, such as fever, cough, sore throat, runny nose or body aches. If you're caring for someone with the flu, wear a mask and practice good respiratory hygiene.

High-Risk Groups and Special Considerations

Influenza can pose a greater risk to certain individuals, such as:

  • Children, Elderly and Pregnant Women: These groups have a weaker immune system, making them more susceptible to influenza complications. They need to take extra precautions and consider getting vaccinated.
  • Individuals with Chronic Medical Conditions: People with conditions such as asthma, diabetes, heart disease or weakened immune systems are more likely to experience severe flu symptoms.

These high-risk groups should take extra precautions and consider getting vaccinated.

Travel Considerations to Prevent Influenza

When travelling, there are certain precautions you should take to minimise the risk of influenza transmission:

  • Precautions During Travel: When travelling, especially in crowded areas like airports or public transportation, it is important to follow basic hygiene practices such as washing hands frequently, wearing a mask and maintaining social distancing.
  • Flu Vaccination for Travellers: It is recommended for travellers, especially those visiting high-risk areas or travelling on long-haul flights, to receive a flu vaccine before their trip. This can help protect them from contracting the flu and reduce the risk of spreading it to others.


By following the guidelines and recommendations provided by healthcare professionals, you can greatly reduce your risk of infection and protect yourself and those around you. Remember to get vaccinated annually, practice good hygiene and maintain a healthy lifestyle to reduce your risk of developing influenza. If you experience the signs of influenza, talk to a specialist.

Consult Apollo’s Infectious Disease Specialist 



Q. When should I get vaccinated against influenza?

It is recommended to get vaccinated before the flu season starts, ideally in September or October. However, vaccination can still be beneficial later in the season.

Q. Can I still get influenza if I have been vaccinated?

The flu vaccine is not 100% effective but reduces the risk of illness and severity of symptoms if you do contract the virus.

Q3 Can I still go to work or school if I have influenza?

It is recommended to stay home and avoid close contact with others until at least 24 hours after the fever has resolved, to prevent spreading the virus.

Q. Are there any side effects of the influenza vaccine?

Most people who receive the influenza vaccine experience no side effects. Common side effects, if they occur, are mild and may include soreness at the injection site or low-grade fever.

Q. How long does influenza last?

Influenza symptoms usually resolve within 7–10 days. However, fatigue and weakness may persist for several weeks.




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