Orthomyxoviridae

Today’s post is about the flu. Orthomyxovirus gets its name from the Greek word ‘myxo’ which means mucus. In Orthomyxoviridae, there are 5 genera. But I would talk about the taxonomy of flu and more specifically on Influenza A. But I will first give a brief introduction on influenza.

Influenza virus types A and B are both common causes of acute respiratory illnesses. Both virus types may cause epidemics of considerable morbidity and mortality but influenza B infections are often limited to localized outbreaks whereas influenza A viruses are the principal cause of larger epidemics including worldwide pandemics. Influenza can be contracted throughout the year in tropical regions and its contribution to overall morbidity and mortality is less well defined. Orthomyxoviridae is typically spherical, enveloped and can appear in many forms. It is a single stranded RNA in 8 segments.

Influenza A viruses are further classified, based on the viral surface proteins hemagglutinin(HA or H) and neuraminidase(NA or N). Sixteen H subtypes (or serotypes) and nine N subtypes of influenza A virus have been identified.

Diagram of influenza nomenclature

http://www.ipedia.net/information/Orthomyxoviridae

Further variation exists; thus, specific influenza strain isolates are identified by a standard nomenclature specifying virus type, geographical location where first isolated, sequential number of isolation, year of isolation, and HA and NA subtype. Some examples are (A/Moscow/10/99) and (B/Hong Kong/330/2001)