Influenza Viruses Influenza is characterised by fever, myalgia, headache and pharyngitis. In addition there may be cough and in severe cases, prostration. There is usually not coryza (runny nose) which characterises common cold infections. |
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Top Articles: | | Avian Influenza (Bird Flu)
What is Influenza?Influenza, commonly known as the flu, is an infectious disease that infects birds and mammals (primarily of the upper airways and lungs in mammals) and is caused by an RNA virus of the Orthomyxoviridae family (the influenza viruses). The most common and characteristic symptoms of influenza in humans are fever, sore throat, myalgia (muscle pains), severe headache, cough, and malaise (weakness and fatigue).
The term influenza has its origins in 15th century Italy, where the cause of the disease was ascribed to unfavorable astrological influences. What is avian influenza or bird flu?Avian influenza or 'bird flu' is a highly contagious disease of birds, caused by influenza A viruses. In another way Avian influenza, or “bird flu”, is a contagious disease of animals caused by viruses that normally infect only birds and, less commonly, pigs.It is also called bird flu, avian influenza and bird influenza.Domesticated birds may become infected with avian influenza virus through direct contact with infected waterfowl or other infected poultry, or through contact with surfaces (such as dirt or cages) or materials (such as water or feed) that have been contaminated with the virus.Infection with avian influenza viruses in domestic poultry causes two main forms of disease that are distinguished by low and high extremes of virulence. The “low pathogenic” form may go undetected and usually causes only mild symptoms (such as ruffled feathers and a drop in egg production). However, the highly pathogenic form spreads more rapidly through flocks of poultry. This form may cause disease that affects multiple internal organs and has a mortality rate that can reach 90-100% often within 48 hours.Usually, “avian influenza virus” refers to influenza A viruses found chiefly in birds, but infections with these viruses can occur in humans. "Avian flu", "bird flu", "avian influenza", and "bird influenza" all technically mean "flu from Influenza A viruses which is adapted to birds".There are many different subtypes of type A influenza viruses. These subtypes differ because of changes in certain proteins on the surface of the influenza A virus (hemagglutinin [HA] and neuraminidase [NA] proteins). There are 16 known HA subtypes and 9 known NA subtypes of influenza A viruses. Many different combinations of HA and NA proteins are possible. Each combination represents a different subtype. All known subtypes of influenza A viruses can be found in birds. Avian Influenza A (H5N1)Influenza A (H5N1) virus – also called “H5N1 virus” – is an influenza A virus subtype that occurs mainly in birds, is highly contagious among birds, and can be deadly to them. H5N1 virus does not usually infect people, but infections with these viruses have occurred in humans. Most of these cases have resulted from people having direct or close contact with H5N1-infected poultry or H5N1-contaminated surfaces. There are several types of avian influenza. The strains that cause the greatest number of deaths are called highly pathogenic avian influenza (HPAI). The HPAI strain involved in the current outbreak is called H5N1. It was first recognized in 1997 in Hong Kong, where it caused poultry outbreaks and led to infections in 18 people with 6 deaths. Fortunately, the outbreak was halted in Hong Kong at that time by strict control measures in the poultry industry. | Bird Flue Three prominent subtypes of the avian influenza A viruses that are known to infect both birds and people are: - Influenza A H5
- Influenza A H7
- Influenza A H9
Avian influenza virus usually refers to influenza A viruses found chiefly in birds, but infections can occur in humans. |
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