Person-to-Person Bacterial and Viral Diseases - Influenza

5 important questions on Person-to-Person Bacterial and Viral Diseases - Influenza

What are the three classes of influenza viruses, and why is influenza A considered the most important human pathogen?

The three classes of influenza viruses are influenza A, B, and C. Influenza A is considered the most important human pathogen due to its significant impact on human health and its ability to undergo antigenic drift and shift.

Explain the concept of antigenic drift and its implications for influenza viruses.

Antigenic drift refers to minor changes in the amino acid sequence of surface glycoproteins (HA and NA) of influenza viruses over time. These changes can reduce host immunity, leading to reinfection. This phenomenon is why last year's influenza vaccine may not be highly effective against this year's influenza viruses.

What is antigenic shift, and how does it contribute to the emergence of novel influenza virus strains?

Antigenic shift is a major change in a surface antigen of influenza viruses, resulting from the total replacement of the RNA that encoded it. It occurs through reassortment, where gene fragments between different strains of influenza virus mix. This process creates novel reassortant viruses that are essentially unrecognized by the immune system, contributing to the emergence of new strains.
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Describe the symptoms of human influenza and its potential complications.

Symptoms of human influenza include a low-grade fever, chills, fatigue, head and muscle aches, cough, sore throat, and general malaise. Complications, especially in vulnerable populations, can arise from bacterial secondary infections, such as pneumonia.

How are influenza epidemics controlled, and why is developing an effective vaccine challenging?

Influenza epidemics are controlled by immunization. However, developing an effective vaccine is challenging due to the large number of existing influenza viral strains resulting from antigenic drift and shift. Annual vaccines are prepared based on samples of major emerging strains obtained through worldwide surveillance.

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