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RNA VIRUSES

ORTHOMYXOVIRUS
(influenza viruses)
- 3 antigenic types (A, B, C)
- A: has great antigenic variability
- B: has lower antigenic variability
- C is relatively stable
- the antigenic variability results from the combination of the segmented RNA ( 8 segments)
Laboratory diagnosis
I. Direct diagnosis
1. Samples: pharyngeal and nasal exudates, nasal and pharyngeal washing, necroptic fragments
2. Influenza antigens may be demonstrated within the epithelial cells using fluorescent antibodies.
3. Isolation: on embrionated egg (in amniotic or alantoidian liquid) or cell culture
4. Identification is made mainly by hemagglutinoinhibation with specific serum
using cock (rooster) erythrocytes.
Other techniques for identification: complement fixation
II. Serologic tests
Are based on the at least four-fold rising of antibodies titer in the serum collected in convalescence.
Hemagglutinoinhibation (HIA)
-place diluted serum in a plate with wells
-place standard......

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