SeminarInfluenza
Section snippets
Virology
Influenza viruses are enveloped particles with two surface glycoproteins—haemagglutinin and neuraminidase. Influenza viruses belong to the family Orthomyxoviridae, which includes four genera: influenzavirus A, influenzavirus B, influenzavirus C, and thogotovirus.3 Influenza A and B viruses contain eight single-stranded, negative-sense RNA segments that encode at least ten polypeptides, of which eight are structural viral proteins, and two are found in infected cells.
Influenza A viruses are
Epidemiology
Influenza viruses are unique in their ability to cause both recurrent annual epidemics and more serious pandemics that spread rapidly and may affect all or most age-groups. The size of epidemics and pandemics, and their relative impact, reflects the interplay beween the extent of antigenic variation of the virus, the amount of protective immunity in populations, and the relative virulence of the viruses. Although the epidemiology of influenza has been studied extensively since the virus was
Clinical illness and complications
Influenza in adults and adolescents typically presents with an abrupt onset of fever and chills, accompanied by headache and sore throat, myalgias, malaise, anorexia, and a dry cough. Fever (38–40°C) peaks within 24 h of onset and lasts 1–5 days. Physical signs include the appearance of being unwell, hot and moist skin, flushed face, injected eyes, hyperaemic mucous membranes, and a clear nasal discharge. Although several of the symptoms of influenza are common to all age-groups, a review of
Laboratory diagnosis
A definitive diagnosis of influenza requires laboratory confirmation. There are several new diagnostic tests for influenza available or soon to be available. Diagnostic tests for influenza fall into four broad categories: virus isolation, detection of viral proteins, detection of viral nucleic acid, and serological diagnosis. The best clinical sample to use with the first three diagnostic methods is a combination of nasopharyngeal and throat swabs. The importance of appropriate collection and
Control and prevention
The two approaches available for the control and prevention of influenza are the use of vaccines and the use of antiviral agents.
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