Podcast
Questions and Answers
What type of immunity is primarily involved in producing antibodies against HA and NA proteins?
What type of immunity is primarily involved in producing antibodies against HA and NA proteins?
- Innate Immunity
- Humoral Immunity (correct)
- Adaptive Immunity
- Cellular Immunity
Which of the following is NOT a complication associated with influenza?
Which of the following is NOT a complication associated with influenza?
- Chronic hypoxia (correct)
- Secondary bacterial pneumonia
- Encephalitis
- Myositis
Influenza A can be categorized by which antigens?
Influenza A can be categorized by which antigens?
- PA and CA antigens
- XA and MA antigens
- HA and NA antigens (correct)
- GD and PD antigens
Which subtype of influenza primarily affects cattle and is not pathogenic to humans?
Which subtype of influenza primarily affects cattle and is not pathogenic to humans?
What is the estimated annual attack rate of influenza in adults?
What is the estimated annual attack rate of influenza in adults?
Which of the following factors does NOT increase the risk for severe influenza complications?
Which of the following factors does NOT increase the risk for severe influenza complications?
Which antibody type plays a key role in inhibiting viral entry into host cells?
Which antibody type plays a key role in inhibiting viral entry into host cells?
The incubation period for influenza typically ranges from how many hours?
The incubation period for influenza typically ranges from how many hours?
What is a key characteristic of influenza B viruses?
What is a key characteristic of influenza B viruses?
Which of the following does NOT aid in the transmission of influenza?
Which of the following does NOT aid in the transmission of influenza?
Flashcards
What are the main types of influenza viruses?
What are the main types of influenza viruses?
Influenza viruses are categorized into four types: A, B, C, and D. Type A is further divided into subtypes based on HA and NA antigens, with 18 H subtypes and 11 N subtypes. Examples of human-infecting subtypes include H1, H2, H3, N1, and N2.
How is influenza transmitted?
How is influenza transmitted?
Influenza is spread via respiratory droplets released by coughing or sneezing. It can also be transmitted through fomites, contaminated surfaces.
How does the influenza virus enter the host's cells?
How does the influenza virus enter the host's cells?
The virus attaches to sialic acid receptors on the respiratory mucosa, permitting entry into cells.
What happens once the influenza virus enters the cells?
What happens once the influenza virus enters the cells?
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What role does the host's immune system play in fighting influenza?
What role does the host's immune system play in fighting influenza?
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What are the typical symptoms of uncomplicated influenza?
What are the typical symptoms of uncomplicated influenza?
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What are some potential complications of influenza?
What are some potential complications of influenza?
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What is the epidemiological pattern of influenza?
What is the epidemiological pattern of influenza?
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Who are at increased risk for influenza complications?
Who are at increased risk for influenza complications?
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What is a flu pandemic and what are some historical examples?
What is a flu pandemic and what are some historical examples?
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Study Notes
Influenza Virus
- Influenza viruses are classified into four genera: A, B, C, and D
- Influenza A subtypes are based on HA and NA antigens
- Influenza A has 18 H subtypes (H1 to H18) and 11 N subtypes (N1 to N11)
- Most subtypes infect animals and birds, but some can infect humans
- Influenza B viruses are not classified into subtypes but have lineages (B/Yamagata or B/Victoria).
- Influenza C virus is rare, causing mild infections
- Influenza D primarily infects cattle and is not pathogenic to humans
Influenza Virus Pathogenesis
- Transmission through respiratory droplets, coughing, and sneezing
- Respiratory droplets infect those within a 1-meter distance
- Viruses attach to sialic acid receptors on respiratory mucosa
- Viral replication in infected cells, spreading locally and adjacent cells
- Spread to lower respiratory tract or blood stream
- Cellular destruction and desquamation of superficial mucosa causing local damage, potentially preceding secondary bacterial infections
Host Immune Response
- Humoral immunity plays a major role, providing subtype-specific, long-lasting resistance
- Antibodies against HA and NA are protective, preventing infection or transmission
- Antibodies to NA decrease the severity of the disease and prevent the virus from entering contacts
- Antibodies targeting ribonucleoprotein are type-specific
- All influenza A, B, and C viruses are antigenically unrelated
- Immunity may be incomplete following infection, allowing for reinfection
- Cell-mediated immunity and innate immunity (e.g., cytotoxic T cells, NK cells, interferons) also contribute to immunity
Clinical Manifestations
- Incubation period averages 18-72 hours, depending on inoculum size and host immunity
- Uncomplicated cases are asymptomatic or mild, showing symptoms like fever, myalgia, headache, and dry cough
- Complications include secondary bacterial pneumonia, causing worsened respiratory illness
Epidemiology
- Influenza causes seasonal epidemics globally, varying in severity
- Annual incidence is estimated at 3-5 million severe cases and 300,000 deaths
- Global pandemics occur approximately every 10-40 years
- Influenza outbreaks are common during winter months, varying geographically
- Risk factors for complications include age (<2 or ≥65 years), chronic diseases, immunocompromised states, and other health factors
History of Influenza Outbreaks
- Multiple pandemics and outbreaks have occurred throughout history.
- The Spanish flu pandemic of 1918-1919 had a high mortality rate (potentially >50 million deaths). The strain originated from an avian source adapted to humans (and pigs).
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Description
This quiz explores the classification and pathogenesis of influenza viruses, detailing the four genera: A, B, C, and D. It further examines how influenza A subtypes are determined and their transmission mechanisms, including the impact on human health. Test your knowledge on these vital aspects of virology!
