The influenza virus has -
Influenza virus

 Belong to orthomyxoviridae → Envelope, RNA virus
 Contain single stranded RNA which is segmented → 8 pieces
 There are three viral subtypes

1. Type A → Causes all pandemics and most of the epidemics
2 Type B → Can cause epidemics
3. Type C → Causes endemic infection

 Three types of influenza viruses are circulating in world →A(H1N1), A(H3N2) and B
 A new type has been recognized →A (H5N1)
 Source of infection → Case or subclinical case
 Mode of transmission → Droplet infection by respiratory route
 Incubation period → 18-72 hours
 Clinical manifestations

Most infections are subclinical
Fever, headache and myalgia
Respiratory → coughing
There is no viremia

 Complications

Pneumonia → M.C. by str. pneumoniae
Worsening of COPD
Encephalitis
Reye’s Syndrome→ with type B virus
GB. Syndrome
GI Symptoms (gastric flu)→ Type B virus

 Laboratory diagnosis

Most commonly, the diagnosis is established by the use of rapid viral tests that detect viral nucleoprotein or neuraminidase.
5 segments of SS RNA
8 Segments of ds DNA
8 segments of ssDNA
8 segments of ssRNA