Chapter 60 Orthomyxoviruses Medical Microbiology Chapter 60 Orthomyxoviruses

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

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)

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 20-40 million people died worldwide Subsequent pandemics have occurred in 1947, 1957, 1968, and 1977. Table 60-2

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