1. Chapter 60 Orthomyxoviruses
Medical Microbiology
Chapter 60
Orthomyxoviruses

2. Orthomyxoviruses Structure: Enveloped virus
Single-stranded RNA genome (linear)
8 segments – this allows for the production of new strains of virus through reassortment
The structure of the influenza virus includes:
an envelop having 2 different kinds of protein spikes:
H-spikes allow the virus to attach to a host cell
N-spikes are involved in penetration into the cell
Figure 60-1

3. Influenza Virus
The influenza virus is the etiological agent of influenza or the “flu”
Infection occurs in the upper respiratory system
Virus can spread to the lungs
Increases the likelihood of a secondary bacterial pneumonia infection
This is the primary cause of serious disease and death
90% of deaths occur in patients older than 65
Classic flu symptoms are associated with interferon release (fever, malaise, headache, myalgia)

4. Influenza Virus (cont.)
Recurring epidemics are possible because of changes in the antigens (the H and N-spikes)
Antigenic drift (mutation) and Antigenic shift (rearrangement)
Pandemic of 1918 (Spanish Flu)
the US reported 548,452 deaths over a period of a few months
it is estimated that million people died worldwide
Subsequent pandemics have occurred in 1947, 1957, 1968, and 1977.
Table 60-2

5. Influenza Virus (cont.)
Box 60-2 and 60-3