Lecture 7: Influenza

What family do influenza viruses belong to?

Orthomyxoviridae

What type of genetic material do influenza viruses have?

Single stranded RNA

What makes influenza viruses highly able to mutate?

Low fidelity polymerase and segmented genome

How many types of influenza viruses are there based on nucleoprotein and matrix proteins?

Three types: A, B, C

What are the two surface glycoproteins used to subtype influenza A?

Hemagglutinin (HA) and Neuraminidase (NA)

How many subtypes of HA are there?

16 subtypes

How many subtypes of NA are there?

9 subtypes

What is the natural reservoir for influenza viruses?

Wild waterfowl, gulls, and shorebirds

Which influenza serotypes have established themselves in humans?

H1N1, H2N2, H3N3, and H5N1

What historical pandemic is associated with H1N1?

The Spanish flu (1918-1919)

What was the estimated death toll of the 1918 influenza pandemic?

50-100 million deaths

What is antigenic drift in influenza viruses?

Frequent, minor changes in HA and/or NA antigens

What is antigenic shift in influenza viruses?

Introduction of an influenza A subtype to which the population has no immunity

What is the incubation period for influenza?

2-8 days (median 4 days)

What are common clinical signs of influenza?

Fever, headache, sore throat, myalgia, upper respiratory symptoms, and GI issues like diarrhea

Which populations are at high risk for influenza complications?

Patients

What is the gold standard for diagnosing influenza?

Viral culture and immunofluorescent staining

What are the two main categories of antiviral treatments for influenza?

M2 protein blockers (e.g., amantadine) and NA inhibitors (e.g., oseltamivir)

What is the main method of influenza transmission in humans?

Respiratory droplets

What is the primary control measure for influenza?

Vaccination, especially for high-risk patients

What is H5N1 also known as?

Highly pathogenic avian influenza (HPAI)

What are common transmission routes for H5N1 to humans?

Butchering, consuming raw poultry, and handling infected birds

What is a significant challenge in diagnosing H5N1?

Patients are often deceased, requiring BSL-3 lab work

What is a potential future pandemic strain of influenza?

Bird flu H5N1

What are the clinical signs of H5N1 infection?

Similar to H1N1, but more likely to cause GI disturbances and faster progression

What measures can improve control of H5N1 in chickens?

Increased biosecurity, vaccination, and culling infected birds

What is the role of pigs in influenza transmission?

Pigs express both a2,3- and a2,6-Gal, facilitating cross-species transmission

What is the significance of the HA glycoprotein in influenza?

It determines receptor specificity and the ability to cross species barriers