Causes of Influenza

When comparing influenza (commonly known as the flu) to other viral respiratory illnesses such as the common cold, influenza typically results in more severe symptoms and lasts longer. While over 100 different viruses can trigger colds, influenza is caused specifically by influenza viruses of types A, B, or C. Influenza types A and B are responsible for most respiratory disease epidemics that occur nearly every winter. In contrast, influenza type C often leads to a much milder respiratory illness or may even present no symptoms at all, and it is not considered an epidemic nor does it pose a significant public health risk. It is important to note that the influenza vaccine is effective only against types A and B. Furthermore, influenza virus type A can infect a wide range of animals, including ducks, chickens, pigs, whales, horses, and seals, whereas type B affects humans exclusively.

Risk Factors for Influenza

Several factors can increase the likelihood of contracting influenza or experiencing complications associated with it, including:

Age: Seasonal influenza tends to affect young children and the elderly more severely than other demographics.
Living or Working Conditions: Individuals residing or working in crowded environments are at a heightened risk of developing influenza.
Weakened Immune System: A generally weakened immune system makes the onset of influenza more likely and elevates the risk of complications.
Chronic Diseases: Conditions such as asthma, diabetes, or heart problems can significantly increase the risk of influenza-related complications.
Pregnancy: Particularly during the second and third trimesters.
Obesity: Individuals with a body mass index (BMI) of 40 or higher face a greater risk of influenza and its complications.

Transmission of Influenza

Influenza is a highly contagious illness that spreads rapidly among individuals in homes, schools, and workplaces. The flu virus is transmitted from person to person through coughing or sneezing, which releases droplets into the air. If these droplets are inhaled or come into contact with the nose or mouth of another person, they can become infected as well. Transmission can also occur through handshakes, hugs, and by touching contaminated surfaces. Research indicates that individuals infected with influenza may be contagious one day before symptoms appear and can continue to spread the virus for up to five to seven days after becoming ill. This implies that a person may transmit the infection to others even before realizing they are sick.