Influenza Virus – Symptoms, Causes, Treatments, and Risk Factors

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The influenza virus is a viral infection that infects the human respiratory system. It is also called as a flu virus, and it causes cold and fever in the infected people. Sometimes, people infected with the influenza virus will not require any treatment and will resolve on their own.  

However, in some cases, it can cause major complications and would require treatment. Elderly people and kids under the age of 5 are more prone to such an influenza virus. People with a weakened immune system are also prone to flu infections.

Four types of influenza virus infect humans—A, B, C and D. Among the four categories, the A-type virus has the ability to cause a pandemic.

It can form new strains, and the disease-causing gene can differ from one strain to another, which makes it difficult to treat the virus. The A-type can also spread easily from one person to another.

The type B and C viruses can cause seasonal flu, and the type D virus commonly infects cattle. Type D usually do not infect humans.

Symptoms of Influenza Virus

The symptoms of the influenza virus mostly resemble a normal cold. People infected with a cold can see their symptoms develop slowly with a runny nose and sneezing.  However, a person infected with flu might have major discomfort. Some of the common symptoms are discussed below.


Fever is a common symptom of flu. People infected with flu will have an increased body temperature.

Aching muscles

Body pain and muscle ache are caused due to the viral infection. The virus, after entering the body, causes damage to the cells and muscles, which leads to pain in the muscles. After the virus leaves the body, the pain subsides.

Chills and sweats

The signs of flu include chills and sweat. Sweating and chills can be accompanied by body aches.


Headache is also one of the common symptoms of the influenza virus. When a person is infected with the influenza virus, it causes inflammation in the sinus cavity and nasal lining. This inflammation causes increased pressure around the face and eyes, which can lead to a magnified headache.

Sore throat

A sore throat and stuffy nose can be common symptoms of the influenza flu. The virus infects the respiratory tract, which leads to sore throat, stuffy nose, runny nose and sneezing.

Eye pain

The influenza virus infects the respiratory tract, which leads to swelling of the nose cavity. This can lead to eye pain.

Causes of Influenza Virus

The causes of the influenza virus are listed below.

Young children under the age of 5

Children below age 5 are prone to flu virus infection and complications, especially children below the age of 2. This is because their immune system will not be fully developed. This group is called the immunologically naive population.

Their immune system will be handling these infections and fighting against them. Once they become adults, they might get protection against this flu and virus. Children might not practise self-hygiene properly, which can lead to recurrent infections.

Adults older than 65years

Older aged people have weakened immune systems. Their body cells would have also aged, which can lead to frequent flu infections.

Residents of nursing homes and other long-term care facilities

Residents of a nursing home are vulnerable to the influenza virus. They are prone to other respiratory pathogen infections. The infection can spread through staff, new residents or visitors.

These outbreaks can cause major health illnesses and can lead to community spread. Long-term facility care is an umbrella term for a rehabilitation centres, nursing homes, psychiatric care and long-term care hospitals.

When there is an influenza virus outbreak in these care centres, it will be challenging to control the spread and treat it.

Pregnant women and women up to two weeks after giving birth

Respiratory diseases can cause major complications, especially when a woman is pregnant. It can also lead to pneumonia and sometimes be deadly.

According to the Centre for Disease Control and Prevention, changes during the pregnancy period can alter the immune system, lungs and heart during pregnancy. These factors make pregnant women more vulnerable to such infections.

People with weakened immune systems

People with a weakened immune system are prone to respiratory tract infections. When people infected with flu sneeze or cough, droplets of flu infection get deposited on the surface.

When people with a weakened immune system touch the infected surface, they can get infected with the influenza virus. Their immune system cannot fight the infection, and people tend to fall sick.

Treatments of Influenza Virus

The influenza virus treatment helps reduce the severity of the symptoms and shortens the length of the infection period. Some of the treatment methods are discussed below.

Antimicrobial resistance is a problem

Some of the common antimicrobial drugs used to treat influenza viruses are amantadine and rimantadine. These drugs disrupt the ion channels of the virus. This will prevent the replication process of the virus during the initial stages of the infection.

Some of the viruses have become resistant to such drugs, and these drugs are effective in treating influenza A-type viruses.

According to the Centres for Disease Control and Prevention, influenza A virus and H1N1virus have become resistant to adamantanes. These drugs are no longer recommended for the treatment of the influenza A virus.

Most seasonal viruses have also become resistant to other antiviral drugs like zanamivir or oseltamivir.

The report submitted by the Centres for Disease Control and Prevention listed some of the points, and they are listed below.

The influenza A virus developed resistance against the adamantanes drugs, and the percentage of resistance increased rapidly worldwide in the year 2003–2004. The influenza A virus infection rate increased from 0.4% to 12.3% during 2003–2004.

During the influenza season of 2005–2006, the virus isolated from the patients of 26 states was the influenza A virus. Additionally, there was a change in the amino acid sequence 31 in the M2 gene, which confirms the virus’s resistance to adamantanes.

These reports strongly suggest that the influenza A viruses have a strong resistance to adamantanes, and they are no longer recommended for the treatment of the influenza virus.

NIAID Flu treatment Research

For the past years, the influenza virus has shown increased resistance to these drugs and the National Institute of Allergy and Infectious Disease (NIAID) has been in intensive drug development research to treat these influenza viruses effectively.

NIAID has conducted a phase 1 clinical trial for the peramivir, which the Food and Drug Administration approved in 2014. It states that the drug can effectively treat flu in adults.

The peramivir drug is the first neuraminidase inhibitor that is available in the intravenous formulation. These drugs can be treated in patients who cannot take oral drugs.

Additionally, NIAID is in the process of testing next-generation neuraminidase inhibitors, flu RNA polymerase inhibitors and monoclonal antibodies. These drugs target the flu surface protein hemagglutinin.

Home remedies of Influenza Virus

Sometimes bad flu can be treated at home. Influenza virus can be treated at home with certain over-the-counter drugs and home remedies.

Drink plenty of liquids

The influenza virus can make a person tired. This is due to the invasion of foreign pathogens in the body. A person might get dehydrated easily, and it is important to drink a lot of fluids.

Drinking hot water can help reduce pain in the throat and clear the sore throat. Fresh juice can sometimes aggravate your body condition, so it is better to avoid such juices.

After your symptoms settle, you can consume citrus fruit juice to restore the lost nutrients, and vitamin C helps the body to recover soon. So, these fluids will help you stay hydrated.

Alcohol consumption can result in dehydration. The body concentrates on removing the alcohol in the body instead of removing the virus that has currently invaded the body.

Additionally, alcohol interferes with the drugs and medication’s mechanism and alters the effect of these medications. This can slow down the process of healing. So, alcohol consumption should be strictly avoided when you are sick.


Rest is important when a person is sick. Adequate rest will help the body to recover easily from the flu. The body will concentrate more on the healing process than on other energy expenditures.

Sleep can help with the person’s symptoms. Adequate sleep helps to strengthen your immune system and fight the virus effectively.

Pain relievers

Pain relievers can help to reduce body pain and helps you sleep well. Acetaminophen and ibuprofen can help reduce pain and body temperature. These medications can also help you to sleep well.

If the severity of the symptoms does not reduce, consult your doctor and take medications that your doctor prescribes.

Diagnosis of Influenza Virus

There are some common tests available to diagnose the influenza virus. The sensitivity and specificity of the diagnosis method can vary from one laboratory to another.

Viral culture

Viral culture is preferred during an outbreak of respiratory illness. The viral culture can help identify the other causes of the illness.

Respiratory illness requires a collection of the respiratory sample, which can be tested with the help of molecular assays and viral culture. These diagnostic methods can help identify the influenza type A and type B virus.

Rapid antigen testing

Rapid antigen testing is an immunoassay that helps to detect the presence of Influenza type A and type B viral protein antigen in the respiratory sample. However, rapid antigen testing can be less sensitive to the influenza virus.

Immunofluorescence assays

Immunofluorescence assay is an antigen testing method and requires a fluorescent microscope to view the results. The assay requires about 2-4 hours to produce results with high sensitivity and specificity.

Risk factors of Influenza virus

There are certain risk factors for people getting affected by the influenza virus.

Lung disease

People infected with lung disease are more vulnerable to influenza virus infections. Flu infections are highly contagious, and people with other lung diseases and asthma can easily contract the flu infection.

The influenza virus can be life-threatening for people affected by lung diseases. Complications of influenza virus include pneumonia, dehydration, ear infection or Diabetes.

Heart condition

Viral infections like the influenza virus can add stress to the body. When the virus infects people with heart conditions, it can alter the affected people’s heart rate and blood pressure.

These alterations can increase the risk of stroke or heart attacks. People with heart conditions can have a hard time combating the virus.

Diabetes or another metabolic disease

According to an NCBI article, the influenza virus has a link between Diabetes mellitus and infection severity. People with Diabetes can have severe symptoms. In some cases, the infection can be fatal.

Kidney problem

People with chronic kidney infections or diseases have a higher risk of getting infected with the influenza virus. According to the CDC, people with kidney disease have a weakened immune system, and the body becomes susceptible to infections.  

Prevention of Influenza Virus

The influenza virus can be prevented with certain precautionary actions.

Avoid close contact

Influenza viruses are highly contagious, and it is highly recommended to avoid close contact with the affected people.

If you are affected by the influenza virus, be aware of the infection. Avoid contact with other people, as flu can spread easily.

Stay home when you are sick

People infected with the influenza virus may have symptoms for about 4–5 days. The Centres for Disease Control and Prevention recommends people to stay at home when people are sick to avoid the spread of infection.

Cover your mouth and nose

When you are sick, it is advised to cover your mouth and nose with a mask. This will avoid the spread of infection when you sneeze or cough.

Clean your hands

Make sure you wash your hands often with soap and water. The virus can get transmitted through dirty hands when you touch your eyes or mouth. So, it is advised to wash your hands and not touch your face with dirty hands.

Avoid touching your eyes, nose or mouth

Avoid touching your eyes, nose and mouth with dirty hands.

Practice other good health habits

The spread of the influenza virus increases during the monsoon season. So, consume foods that are rich in vitamin C. Do not consume foods that are cold, and drink hot water. These health habits may help you to stay healthy and avoid contracting the infection.


The spread of influenza infection increases during the monsoon season. Avoid close contact with infected people.

Drink hot water and do not consume foods that were cooked before many hours. Consume foods that are hot and do not consume refrigerated foods.


How long does influenza last?

Influenza virus infection lasts for about seven to ten days. People vaccinated with flu shots may have a short period of symptoms, and the complications can also be reduced.

How can you treat influenza at home?

1. Mild influenza infection can be treated at home.
2. Drink boiled water and make sure you consume enough water. When you are infected with influenza, your body might get dehydrated easily. So, it is advised to consume more water.
3. Your body will be tired during an encounter with infection. So adequate rest is required to combat the infection.
4. Sometimes an over-the-counter can help reduce the symptoms. These drugs can help reduce the pain and severity of the symptoms.

Does vitamin C help with flu?

Vitamin C can help reduce the severity of the symptoms. It will help the body to heal from infection easily.

What do I eat when I have the flu?

Consume foods that are rich in vitamins and proteins. This will help the body to restore the lost nutrients and give strength. Foods like garlic, ginger and hot tea will clear a sore throat and blocked nose.


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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