What is Influenza?

Influenza is a communicable viral disease that affects the upper and lower respiratory tract and is caused by influenza viruses. A wide spectrum of influenza viruses causes it, among them there are 4 types of seasonal influenza viruses, types A, B, C and D.

• Influenza A viruses: Subtype A(H1N1) and A(H3N2) influenza viruses are the subtypes currently found affecting humans. Only this type is known to have caused pandemics.
• Influenza B viruses: 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.
• Influenza D viruses primarily affect cattle.

The virus is transmitted through droplets expelled from the mouth during coughing, talking or sneezing, and by touching objects or surfaces soiled with the virus and then touching the nose or eyes. It is contagious before the symptoms appear and till 5-7 days after infection.

Signs and Symptoms

Influenza presents with symptoms ranging from mild to severe depending on the age, comorbidities, vaccination status, and natural immunity to the virus.

In mild cases, there is cough, fever, sore throat, myalgia, headache, runny nose, and congested eyes. A frontal or retro-orbital headache is a common presentation with photophobia and pain in eyes. Severe cases can progress to shortness of breath, tachycardia, and hypotension.

After infection, a full recovery is seen in most cases and it takes a few days, but complications that include pneumonia and death can occur in certain high-risk groups. These groups include young children, the elderly, immunocompromised, and pregnant females.

Influenza spreads rapidly and efficiently in seasonal epidemics. Epidemics occur every autumn and winter in temperate regions and affect a significant portion of adults and children, but seasons differently impact age groups and severity. It can result in high levels of worker/school absenteeism and productivity losses. Globally, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness, and about 290,000 to 650,000 respiratory deaths.

Diagnosis

Diagnosis of influenza is mainly clinical, especially during the influenza season. Most cases recover without treatment, and laboratory tests for the diagnosis are not needed. Laboratory tests available for diagnosis of influenza are rapid antigen detection, a rapid molecular assay for the detection of viral RNA, immunofluorescence direct and indirect antibody staining for detection of viral antigen, real-time PCR test, and cell culture. A chest x-ray is advised in patients with pulmonary symptoms to exclude bacterial pneumonia.

Complications

• Secondary bacterial pneumonia
• Acute respiratory distress syndrome
• Myositis
• Myocarditis
• Multiorgan failure

Management

Influenza is a self-limiting and mild infection in most healthy individuals who do not have other comorbidities.

Apart from vaccination, the public health management advises adoption of personal measures like:

• Regular hand washing with proper drying of the hands.
• Good respiratory hygiene צ 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 oneעs eyes, nose or mouth.

Disclaimer: The information provided herein on request, is not to be taken as a replacement for medical advice or diagnosis or treatment of any medical condition. DO NOT SELF MEDICATE. PLEASE CONSULT YOUR PHYSICIAN FOR PROPER DIAGNOSIS AND PRESCRIPTION.