Chest discomfort, cough Common; can be severe Mild to moderate; hacking cough Headache Common Rare

Laboratory diagnostics • Virus culture – Nasopharyngeal swabs or aspirates – Inoculated onto a cell culture monolayer (Human Fibroblast, Rhesus Monkey Kidney)

– Monitored by light microscopy – Sensitive • Antibody testing – Blood samples – Haemagglutination inhibition assay (HIA) – Enzyme immunoassay (including most rapid tests) 50- 70% sensitivity, 90-95% specificity

• PCR

Viral Haemagglutination assay • HA on flu virus causes RBC to form a lattice – called haemagglutination

• Dilutions of virus mixed with the same quantity of RBC added to a microtitre plate

• Look for when RBC start to show haemaggluntination – viral titre

Haemagglutination inhibition assay

• Carry out haemagglutination assay and determine the HA viral titre

• Add virus to microtitre plate • Add serial dilutions of serum samples to be tested

• Add RBC and incubate • What happens?

The microtitre plate

Virus

Serum

RBC

Red blood cells and flu virus together cause haemagglutination Serum from patients with flu will have antibody against the virusWhen you add red blood cells they are inhibited from binding to the virus

• Any serum samples containing antibodies to influenza will bind to the virus and prevent it sticking to the RBC. Haemagglutination is therefore inhibited.

• Antibodies develop very quickly after flu infection

• Symptoms and presence of antibodies confirm disease

• Antibodies found after disease will confer some protection

Summary

• Influenza caused by influenza virus A, B or C • Influenza A most pathogenic – Antigenic variation – High mutation rate

• HA and NA important for infection and spread of virus

• Highly contagious • Most people can clear the virus • Several tests to diagnose the disease