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All you need to know about Flu (Influenza): Symptoms, causes and treatments

Team AckoFeb 17, 2025

Back in 2018, the WHO mentioned on its website that the Flu or Influenza annually causes bad fever to over five million people in the world. And in the same year, there were 2,90,000 to 6,50,000 deaths reported because of it.

No matter where you are from and how healthy a lifestyle you lead, by now, there have been a few occurrences where you have also caught this fever. And since it is something that mutates rapidly and is very contagious, the chances of getting it again are massive.

Perhaps it is why understanding the symptoms and signs, as well as the treatments of the flu, is a must. If you are looking for these answers, you are in the right place.

Influenza

Contents

What is Influenza (Flu)?
- Flu virus variants
What is the Flu season?
What Causes the Flu?
Symptoms of Flu
Difference between Cold vs Flu
Warning signs of Flu
Progression of a Flu infection
Causes of Influenza
Risk factors for developing the Flu
When To See a Doctor
Treatments for Flu
Prevention of Flu
- What is a Flu shot?
Frequently asked questions
Financial Protection for Future Security and Stability
- Articles related to Different Diseases

What is Influenza (Flu)?

Influenza or Flu is a viral infection that affects the respiratory system of the body. It is highly transmissible and primarily spreads via respiratory droplets. Thus, it is generally passed on while talking or shaking hands.

Flu virus variants

The following are the common Flu virus variants.

Influenza A viruses
Influenza B viruses
Influenza C viruses
Influenza D viruses

What is the Flu season?

Flu season is the typical time every year when the Flu virus tends to break out in a geographical region and then eventually subsides. It usually occurs during the cold months of the year. According to the Centres for Disease Control and Prevention (CDC), the Flu season in India is in full swing during the monsoon seasons (June to September) and again tends to rise in the winter months (November to February).

What Causes the Flu?

The flu is basically caused by the virus. Type B and Type A influenza viruses are the primary cause of flu outbreaks every year. Often, type A is hosted in animals such as ducks and chickens. From there, these get transferred to humans. Type B is found in humans.

Both kinds of viruses are generally found through droplets that enter the air when individuals are infected with sneezing and flu cough. An individual with the flu can spread it to anyone else. You can even get the flu by touching any surface that contains the flu viruses.

Symptoms of Flu

Flu virus symptoms generally start to show up around one to seven days after the virus has entered the body. The following are some of the common Flu symptoms.

Body aches
High fever
Low appetite
Fatigue
Dry cough
Chills
Running nose
Headache

Difference between Cold vs Flu

Chronic Obstructive Pulmonary Disease (Cold) and the Flu are highly transmissible respiratory diseases that share some common symptoms but have different causes. As mentioned earlier, the Flu is caused by the Influenza virus. However, Colds can be caused by multiple different types of viruses.

The following are some of the symptoms that both these respiratory diseases share.

Fatigue
Blocked or runny nose
Sore throat
Cough
Discomfort in the chest

Despite the commonalities in symptoms between Cold and the Flu, there are also major differences. The below-given table shows the key differences in their symptoms.

Symptom	Flu	Cold
Fever	Typical	Rare
Chills	Typical	Rare
Body ache	Intense	Slight
Sore throat	Sometimes	Typical
Cough	Intense	Moderate
Sneezing	Sometimes	Typical
Chest discomfort	Typical	Sometimes
Body ache	Typical	Sometimes
Fatigue	Typical	Sometimes

Warning signs of Flu

The below-mentioned table shows the warning signs of the Flu in children and adults. If you or your child develops any of these symptoms, get medical attention at the earliest.

Warning signs of Flu in children	Warning signs of Flu in adults
Sore muscles, Breathing difficulty, Chest discomfort, Seizures, High fever, Contracting ribs while breathing, Recurring cough and fever, Bluish face or lips, Dehydration, Worsening of preexisting health conditions, Inability to focus	Inability to urinate, Chest discomfort, Breathing difficulty, Seizures, Weakness, Confusion, Dizziness, Worsening of preexisting health conditions, Recurring cough and fever, Sore muscles

Progression of a Flu infection

Here’s how the Flu virus develops in your body.

The virus enters the body either through the eyes, nose or mouth.
After around 24 hours, the person may be able to transmit the virus to others through close contact.
Symptoms may start to appear after one or two days from the beginning of the infection.
The transmissibility of the virus reaches its peak around three or four days after the symptoms develop.
After around four days from the start of the infection, the muscle aches and fever start to subside.
After the completion of around a week, most symptoms fade away.
The transmissibility of the virus starts to decrease from the fifth day since the initiation of the symptoms.
Some symptoms of the Flu like cough and tiredness may subside only after the completion of one more week.

Causes of Influenza

Influenza is usually transmitted in the air when a person with the infection sneezes, coughs or talks. You can catch the Flu through droplets in the air or by touching objects that the infected person has touched and subsequently touching your own eyes, nose or mouth. The Flu virus can spread even before the onset of its symptoms and is generally contagious up to five days from the start of the infection. The disease is typically contagious for a longer duration in children and individuals having a compromised immune system.

Risk factors for developing the Flu

The following factors make you more susceptible to developing the Flu.

Age: Influenza tends to develop more in young children (below the age of 5 years) and older adults (above the age of 65). Also, youngsters under the age of 19 undergoing aspirin therapy are likely to develop a health condition called Reye's Syndrome if they get infected with the Flu.
Obesity: Individuals with an above-normal body mass index are at an increased risk of developing Flu-related health complications.
Compromised immune system: Certain treatments and medications for HIV/AIDS, cancer and organ transplant procedures may temporarily suppress your body’s immune response. This may increase the risk of you catching the Flu and developing further complications.
Living or working environment: Individuals residing in a crowded place like an old-age home or a hostel are more prone to Flu. Professionals working in a hospital environment are also at higher risk of catching the disease.
Pregnant women: In their second and third trimesters, pregnant women are more prone to developing Flu-related complications. This threat is also there for women who have completed two weeks since their child's delivery.
Chronic illnesses: Suffering from certain chronic pre-existing health conditions like metabolic disorders, asthma and heart disease may increase your risk of developing Influenza-related complications.

When To See a Doctor

Make an appointment with your child's physician or other healthcare provider if they have:

A high fever
- exhibits a temperature of 100.4°F (or 38°C) or greater and is younger than three months.
- Has reached the age of more than three months and a temperature:
  - Of 104°F (40° C) or above
  - Above 102°F (38.9° C)
  - That has been attempted to be reduced, but it has not succeeded.
- Has a fever at any age and:
  - Appears extremely sick, cranky, or sleepy.
  - Has a sore throat, a severe headache, or a stiff neck.
  - Possesses an odd rash.
  - Have immune system disorders such as sickle cell disease cancer, or use medications that compromise the immune system, increasing their risk of illness.
Lack of desire to eat or drink, little to no appetite, or symptoms of dehydration such as:
- Doesn't urinate or pee
- Urine has a dark tone.
  - A newborn (born between 0 and 4 months) changes less than 6 diapers in a day.
  - Less than three wet diapers or fewer than three urinations per day are experienced by the youngster (4 months or older).
- Mouth that feels sticky or dry
- Breathing forcefully or quickly
- When crying but no signs of tears
- Eyes that appeared sunken
- A flat, sunken, or pulled-in soft place on the skull
- Persistent stomach pain (bellyache)
- Lethargic, difficult to wake up, disoriented, or unsure of their actions
Any more signs or symptoms that worsen or stay the same

Treatments for Flu

Flu is generally treated at home. The following are some of the treatment methods.

Painkillers can help to relieve body pain and headache.
There are other over-the-counter antiviral medications you can buy as per your doctor’s recommendations.
Drink plenty of fluids like juices and soups to combat dehydration.
Get more rest. This may give your immune system a better chance of fighting off the infection rapidly.

Prevention of Flu

Here are some tips that may help you avoid catching the Flu.

Avoid contact with people who have symptoms of the Flu.
Wash your hands regularly and maintain good hygiene.
Since smoking can aggravate Influenza, it is advisable to avoid or minimise it.
Eat regularly and maintain a healthy diet. This will strengthen your immune system and prevent the development of diseases.

What is a Flu shot?

An annual Flu shot or vaccination is the most effective way to prevent the development of Flu. It is injected into the body via the arm and can be taken by anyone older than six months. Another method for vaccination is the nasal-spray Flu vaccine. As its name suggests, this vaccine is administered through the nose.

Frequently asked questions

Here are the answers to some of the most commonly asked questions about the Flu.

Do antibiotics help with treating the flu?

No, consuming antibiotics is not a treatment for Influenza. Antibiotics are medications used to treat bacterial infections. Influenza is a viral infection and so is generally treated with antiviral medication.

Can babies receive a Flu shot?

No, babies cannot receive a Flu shot. This is because it may be harmful to them.

Is it advisable to receive a Flu shot during pregnancy?

Yes, a pregnant mom can get a Flu shot. This will safeguard herself and her child from the Flu virus.

What is stomach flu?

Stomach flu typically develops in the digestive system of the body and is different from Influenza. It is caused by the consumption of contaminated food items.

Do I need to visit a doctor if I have caught the Flu?

Usually, you do not need to visit a doctor if you develop the Flu since it can be treated at home. However, visit a doctor if you fulfil one or more of the following conditions.

You suffer from a preexisting health condition.
You have a weakened immune system due to the consumption of medication or some disease.
If you are below the age of five years or above the age of 65 years.
If your temperature doesn’t decrease after four to five days of continuous fever.
If the Flu symptoms get worse.
If you have difficulty breathing or suffer chest pain.

References:

https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)

https://www.cdc.gov/globalhealth/countries/india/anniversary-report/program-area-influenza.html

https://www.cdc.gov/flu/symptoms/coldflu.htm

Disclaimer: The content on this page is generic and shared only for informational and explanatory purposes. It is based on several secondary sources on the internet. As this content piece is not vetted by a medical professional, please consult a doctor before making any health-related decisions.

Financial Protection for Future Security and Stability

While health insurance safeguards your immediate medical needs, it is equally important to think about the long-term financial security of your loved ones. This is where term insurance steps in. For example, the best term insurance plan for 1 crore provides substantial coverage, helping your loved ones cope with the costs of medical treatment, lost income, or other expenses in your absence.

If you are considering purchasing a life insurance plan, utilising a life insurance premium calculator can help you find the right policy that fits your insurance needs. Remember, life insurance comes in various types, including whole life plans, endowment plans, ULIPs, and term plans. Choose the right policy today and provide financial protection to your loved ones.

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All you need to know about Flu (Influenza): Symptoms, causes and treatments