February 28, 2024

Influenza: Types, Transmission Symptoms, Prevention, Tests

Dr Rajesh Bendre, National Technical Head & Chief Pathologist, Apollo Diagnostic

Influenza, commonly known as the flu, is a respiratory illness caused by Influenza RNA viruses. There are 2 main types of Influenza virus, namely Types A and B which cause most human illness and that are responsible for flu seasons each year. Type A viruses cause the greatest morbidity and mortality. Seasonal Influenza is caused by several circulating Influenza viruses such as Influenza A Subtypes – HI N l (Swine flu), H3N2, H2N2, Influenza B, etc. The Pandemic Influenza A (H1N1 or Swine Flu) 2009 virus that caused the Pandemic [2009-2010] continues to circulate causing outbreaks of Seasonal Influenza in various parts of the country.

Everything about Influenza: It tends to occur more frequently after the monsoon season and can impact people of all ages. Young children and individuals over 65 years old have a higher likelihood of being affected worldwide. Those working in healthcare, as well as individuals with underlying health conditions like lung disease, heart disease, liver disease, kidney disease, blood disorders, or diabetes, and those with compromised immune systems are at increased risk.

Transmission: Flu is airborne which means it can spread from person-to-person, through large droplets generated by the act of coughing and sneezing. These infectious droplets are highly contagious and when inhaled by an otherwise healthy person can affect them. There are other modes of transmission, including indirect contact by touching a contaminated object or surface (fomite transmission) or close contact (including shaking hands).

Signs and Symptoms

  • Fever: 100.4F/higher temperature or feeling feverish/chills
  • Cough
  • Sore throat
  •  Headaches and body aches
  • Difficulty breathing or shortness of breath
  • Fatigue
  • Runny or stuffy nose

Primary prevention of flu: – Preventing transmission of the influenza virus is a multi-faceted approach including covering the nose and mouth with a tissue when coughing or sneezing and washing your hands. Wearing a mask helps protect you and others from the flu and all other respiratory illnesses including COVID-19. Washing your hands regularly and using alcohol-based sanitizer is recommended. Avoid touching your face, periodically clean and disinfect the surfaces, getting yourself vaccinated with a seasonal flu shot, and staying indoors while you are sick to prevent the spreading of infection to others are also some vital tips that one should follow without fail.

 The diagnostic tests for flu: The treating doctor will advise the following tests and decide the treatment plan accordingly. These Tests aid the clinician in distinguishing influenza from other respiratory viral and/or bacterial infections.

  • Rapid flu tests: Can identify the influenza virus in a throat swab and deliver results in just minutes. Rapid antigen tests for influenza aid in spotting viral antigens in nasal secretions. Nevertheless, the accuracy of the test results is limited, as they can only detect 50-70% of flu cases. In case of a negative result from a rapid antigen test, a molecular test can be conducted as a follow-up.
  • Typically, molecular tests use the methodology of multiplex RT-PCR for targeting influenza A, H1N1, H3N2, and B. There are also other panels which would include Parainfluenza A, B, RSV, adenoviruses & Sars-Cov2.

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