Flu or influenza is an extremely common and contagious febrile infection of viral origin (meaning caused by a virus) affecting the upper respiratory tract and sometimes the lungs also.

Annual flu epidemics can affect all age groups but there are certain risk factors, which increase the flu risk and make you more likely to catch it. People associated with such risk factors are very susceptible and should get themselves vaccinated every year. They should also take care and avoid factors, which spread the flu.

Flu risk factors, which make you more likely to catch it

We have explained 17 factors that can make you more vulnerable to catching the flu infection. If you are associated with one or more of these factors, you should take preventive measures that will help to prevent getting the flu. 

Not taking the flu vaccine

Not taking the flu shot is the most important risk factor because you become totally vulnerable to the flu virus infection. There are compelling reasons why you should take vaccine every year.

When you take the vaccine at the start of the flu season, antibodies to the flu virus build up inside your body. This makes you immune and prepared to fight off the flu virus as soon as it enters your body. Without the vaccine, you don’t have such immediate protection.


Children below the age group of five years and more so below two years are more at risk of getting influenza. This is because their immune system is not fully mature.

People above the age group of 65 years are more susceptible to catching the infection because elderly people have a reduced gag reflex. This typically weakens their immune system due to aging.

Neurological disorders

Certain neurological conditions of the brain, spinal cord, peripheral nerve, and muscle increase your flu risk. Such conditions include cerebral palsy, epilepsy, stroke, muscular dystrophy, multiple sclerosis, Parkinson’s disease, and spinal cord injury.

Why this association? People with neurological conditions have difficulty with muscle function, lung function, or difficulty in coughing, swallowing, or clearing fluids from their respiratory tract. This makes breathing difficult.

Compromised breathing means improper ventilation and lack of oxygen in the blood leading to a compromised immune system.

The flu virus primarily attacks the respiratory tract and makes breathing more difficult. All this can significantly increase the risk of pneumonia, which is a common complication.

Neurological disorders also make it difficult for the body to regulate body temperature. It is the nervous system that is responsible for the body’s temperature control function, its center being in the brain (hypothalamus).

The high temperature associated with flu can, therefore, make your flu symptoms worse. In such people, the chances of a relapse are high.

According to the www.southdevonandtorbayccg.nhs.uk,

“One-third of people with Multiple Sclerosis who catch flu will have a relapse within 6 weeks”.


Heavy smokers have an inflamed airway and the cilia of their respiratory tract are damaged. Cilia are micro hair-like structures, which push the secretions forward to keep the airways clear.

Chronic smokers also suffer from chronic coughing and wheezing, bronchitis and emphysema. Therefore, as flu primarily attacks the respiratory tract, smokers are much more likely to catch the flu virus than non-smokers.

Smokers are also more prone to get complications of flu such as pneumonia. The mortality rate due to influenza is, therefore, significantly higher in smokers than in non-smokers.


The short-term and long-term effects of alcohol are wide-ranging across our body systems. These effects make you vulnerable to various health ailments.

According to Dr. Illhem Messaoudi,

“alcoholics are up to seven times more susceptible to lung infections than the rest of the population, and these lung infections lead to poor health”.

What this indicates is that alcohol abuse weakens your immune system, which makes it easier to catch the flu virus infection.

Alcoholics suffer from a weakened immune system due to  two reasons:

Firstly, alcohol deprives your body of vital nutrients that strengthen your immunity. Secondly, excessive alcohol intake weakens your white blood cells in the blood. This makes them incapable of fighting off bacteria and viruses that invade your body.

Chronic medical conditions

People with certain medical conditions such as chronic diseases of the heart, lungs, kidney, and liver are very prone to catching the flu.

According to the CDC,

“41% of adults hospitalized with the flu during the 2015-2016 flu season had heart disease. Studies have shown that influenza is associated with an increase of heart attacks and stroke”.

Heart diseases can include:

  • Hypertensive heart disease
  • Pulmonary heart disease
  • Valvular disorders
  • Arrhythmias
  • Congenital heart defects
  • Heart failure

It is easy to understand why chronic lung diseases increase your risk because flu is primarily an infection of the respiratory tract. Since the lungs are already weak, it becomes easier for the flu virus to attack the respiratory tract, multiply and cause symptoms.

Such lung diseases include:

People with chronic kidney (kidney failure) and liver disease (chronic hepatitis B and C infection, cirrhosis) have a highly compromised immune system. As a result, it makes it easier for the flu virus to invade the body as the body’s ability to fight off the virus is weakened.

Flu also aggravates the underlying disease making the liver and kidney diseases worse. If you have had a liver or kidney transplant, you are a potential candidate and if infected, the flu can cause your body to reject the new organ.

Diabetes increases your flu risk

People with metabolic conditions such as diabetes are more prone to catching the flu because high sugar levels can weaken the immune system.

Diabetes complications such as neuropathy (nerve damage) and the reduced blood flow to the extremities make the patient vulnerable to infections.

Diabetics are also more prone to flu-related complications like pneumonia.

Certain medical treatments

People who are on treatments, which weaken the immune system such as with steroids or chemotherapy, and those below the age of 19 years who are on long-term aspirin therapy are prone to a higher risk of developing flu.

Genetic disorders

Certain genetic disorders make you susceptible to respiratory tract infections. These disorders include sickle-cell anemia, cystic fibrosis, and Kartagener syndrome. According to The Economist, the gene, which encodes the antiviral molecule called interferon is absent in people with these genetic disorders. This makes them high-risk candidates for the flu infection.


Stress increases your risk of catching the flu in spite of healthy lifestyle habits. Why this happens is not clear, but it is believed that stress alters certain immune factors, which result in inflammation of the airways.


Pregnant women and women up to two weeks post-delivery are more prone to catching the flu. This is because, during pregnancy, the body naturally lowers the immune system to facilitate the growth of pregnancy and avoid rejection of the baby by the body.

The risk is more pronounced in the third trimester when the uterus and the fetus inside compress on the lungs making breathing and coughing more forceful.

According to the Center For Disease Control and Prevention (CDC), pregnant women who catch the flu are at an increased risk of going into premature labor and delivery. Flu also increases the chances of birth defects in the developing baby.

The CDC, therefore recommends taking the flu shot each season even if pregnant regardless of the trimester. The shot does not cause any harm to the pregnant woman or the baby.

Obesity puts you at increased risk

How or why immunity drops because of obesity is still not known, but scientists do maintain that obese people show a higher tendency to catch infections.

Obesity, especially morbid obesity with a BMI of 40 or more, harms the immune system. The immune cells do not show the same efficacy to fight infection as a person with normal weight.

Obese persons are among the list headers of people who should get vaccinated.

Over Exercise

Over exercise lowers your immunity, which predisposes you to catch a cold and flu. Athletes, too, complain of catching a cold or fever after intensive physical activity. If you do have a cold or fever, it is one of the reasons why you should not exercise as it will make your illness more severe.

Flu risk increases during winter

Seasonal incidence is a very important factor, which increases your risk. Flu epidemics or outbreaks are seen in cold climates. This is because the infected droplets sneezed or coughed out in the air from an infected person are able to survive more during these dark and low humidity conditions.

People also stay indoors more during the cold weather making them more exposed to higher concentrations of airborne viruses. Dry winter also dries up the nasal passages, which further increases your susceptibility. It is also believed that darkness (of the cold dry winters) lowers your immunity, which further makes you more prone to getting the flu.

Weakened immunity increases flu risk

People with weakened immunity such as those suffering from HIV, cancer, or patients undergoing organ transplants in whom the immune system is compromised to prevent organ rejection are at a very high risk of getting the flu.

It is the immune system, which neutralizes the bacteria and the viruses that enter the body. A weakened immunity cannot do this efficiently and the invading germs easily multiply and give you the disease.

People with such diseases, which lower immunity, are also prone to flu complications such as pneumonia.

Environmental conditions

Risk increases in people living with others such as health care workers and military personnel living in barracks. Children attending daycare centers and schools are also more prone to catching the flu virus from infected fellow classmates.

Remember that, as mentioned in the post on how flu spreads from person to person, one of the main ways in which it spreads is through the air

A flu-infected individual sneezes and coughs, which releases thousands of viruses into the air. These are inhaled by the neighboring people who become potential candidates for catching the flu.


In America, the Native Americans (American Indians) and the Inuits (Alaskan Natives) are seen to be at a higher risk of catching the flu and its complications.

CDC recommends:

I repeat again, that the best way to defend yourself against the flu is to take the flu vaccination every year. This becomes all the more necessary when you are associated with the flu risk factors.