Influenza - (contact & droplet infection)

 Overview. Seasonal influenza is an acute respiratory infection caused by influenza viruses which circulate in all parts of the world. There are 4 types of seasonal influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease.Jan 12, 2023

Cause

Flu cause

The flu is an illness you get from the influenza virus. It causes symptoms like head and body aches, sore throat, fever and respiratory symptoms, which can be severe. Flu is most common in winter months, when many people can get sick at once (an epidemic).

Most symptoms go away in 4 to 7 days. The cough and tired feeling may last for weeks. Sometimes, the fever comes back. Some people may not feel like eating.

• Influenza A viruses are further classified into subtypes according to the combinations of the hemagglutinin (HA) and the neuraminidase (NA), the proteins on the surface of the virus. Currently circulating in humans are subtype A(H1N1) and A(H3N2) influenza viruses. The A(H1N1) is also written as A(H1N1)pdm09 as it caused the pandemic in 2009 and subsequently replaced the seasonal influenza A(H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics.
• Influenza B viruses are not classified into subtypes, but can be broken down into lineages. Currently circulating influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.
• Influenza C virus is detected less frequently and usually causes mild infections, thus does not present public health importance.
• Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.

Patients with severe or progressive clinical illness associated with suspected or confirmed influenza virus infection

clinical syndromes of pneumonia, sepsis or exacerbation of chronic underling diseases) should be treated with antiviral drug as soon as possible.

More than 3 million US cases per year

Spreads in various ways

Partly preventable by vaccine

Usually self-treatable

Usually self-diagnosable

Lab tests or imaging rarely required

Short-term: resolves within days to weeks

Prevention : vaccination have been used more than 60 years

• Regular hand washing with proper drying of the hands
• Good respiratory hygiene – covering mouth and nose when coughing or sneezing, using tissues and disposing of them correctly
• Early self-isolation of those feeling unwell, feverish and having other symptoms of influenza
• Avoiding close contact with sick people
• Avoiding touching one’s eyes, nose or mouth

indication : WHO recommends annual vaccination for:

• pregnant women at any stage of pregnancy
• children aged between 6 months to 5 years
• elderly individuals (aged more than 65 years)
• individuals with chronic medical conditions
• health-care workers