| influenza | An acute viral infection involving the respiratory tract, occurring in isolated cases, in epidemics or in pandemics striking many continents simultaneously or in sequence. It is marked by inflammation of the nasal mucosa, the pharynx and conjunctiva and by headache and severe, often generalised myalgia. Fever, chills and prostration are common. Involvement of the myocardium and of the central nervous system occur infrequently. A necrotising bronchitis and interstitial pneumonia are prominent features of severe influenza and account for the susceptibility of patients to secondary bacterial pneumonia due to Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus. The incubation period is one to three days and the disease ordinarily lasts for three to ten days. Influenza is caused by a number of serologically distinct strains of virus, designated A (with many subgroups), B and C. Synonym: flu, grippe. (18 Nov 1997) |
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| influenza a | A particular genus of influenza virus. Prone to genetic variability, the influenza vaccine must be updated annually. Symptoms of influenza include fever, muscle aches, headache, malaise, chills, cough and sore throat. (27 Sep 1997) |
| influenza a virus | The type species of the genus influenzavirus a, b that causes influenza and other diseases in humans and animals. Antigenic variation occurs frequently between strains, allowing classification into subtypes and variants. Transmission is by aerosol (human and most non-aquatic hosts) or waterborne (ducks). (12 Dec 1998) |
| influenza a virus, avian | Strains of influenza a virus causing influenza in birds. Transmission is caused by close contact or is waterborne in aquatic species. (12 Dec 1998) |
| influenza a virus, human | Strains of influenza a virus causing influenza and sometimes pneumonia in humans. Transmission is by aerosol. (12 Dec 1998) |
| influenza a virus, porcine | Strains of influenza a virus causing influenza and pneumonia in domestic pigs. (12 Dec 1998) |
| influenza C | Influenza caused by strains of type C influenza virus; the disease is milder than that caused by types A and B and has become uncommon in recent years. (05 Mar 2000) |
| influenza meningitis | <pathology> A form of meningitis caused by the bacterium haemophilus influenza. Inflammation of the membranes (meninges) covering the brain and spinal cord can result after infection with this organism. Influenza meningitis occurs most frequently in children under 5 years old. Onset may be sudden or occur more slowly after an upper respiratory infection. Symptoms and features include fever, headache, stiff neck, photophobia and mental status changes. Infants may be irritable and exhibit poor feeding associated with fever. Severe cases may progress to seizures, coma and death. Treatment always includes high-dose systemic antibiotics and corticosteroids may also be used in some select cases. (27 Sep 1997) |
| influenza nostras | Influenza, usually of a less severe type, occurring with some degree of regularity during the winter season, especially in the larger cities of the world. Synonym: influenza nostras. (05 Mar 2000) |
| influenza type a | A common acute viral infection of the nasopharynx and respiratory tract which occurs in epidemic forms. A common cause is the Influenza a virus. Annual vaccination is recommended for those in high risk groups (health care workers, elderly and immunocompromised) for influenza infection. Common symptoms include runny nose, fever, weakness, headache, body aches, muscle aches, nausea and back pain. Treatment of symptoms has been successful with amantadine or rimantadine. (27 Sep 1997) |
| influenza vaccine | A special vaccine which provides immunity to infection by a variety of Influenza viruses. The vaccine is updated annually due to the constant introduction of new viral strains. Flu vaccination programs are common in the elderly population and any other groups who are at increased risk of viral infection. (27 Sep 1997) |
| influenza virus | <organism, virology> Member of the Orthomyxoviridae that causes influenza in humans. There are three types of influenza virus. Each type of virus has a stable nucleoprotein group antigen common to all strains of the type, but distinct from that of the other type; each also has a mosaic of surface antigens (haemagglutinin and neuraminidase) which characterise the strains and which are subject to variations of two kinds: 1) a rather continual drift that occurs independently within the haemagglutinin and neuraminidase antigens; 2) after a period of years, a sudden shift (notably in type A virus of human origin) to a different haemagglutinin or neuraminidase antigen. The sudden major shifts are the basis of subdivisions of type A virus of human origin. Type A causes the world wide epidemics (pandemics) of influenza and can infect other mammals and birds. Type B only affects humans. Type C causes only a mild infection. Types A and B virus evolve continuously, resulting in changes in the antigenicity of their spike proteins, preventing the development of prolonged immunity to infection. The spike proteins, external haemagglutinin and neuraminidase have been studied as models of membrane glycoproteins. Strain notations indicate type, geographic origin, year of isolation, and, in the case of type A strains, the characterizing subtypes of haemagglutinin and neuraminidase antigens (e.g., A/Hong Kong/1/68 (H3 N2); B/Hong Kong/5/72). (08 Mar 2000) |
| influenza viruses | Virus's of the family Orthomyxoviridae which cause influenza and influenza-like infections of humans and other animals; virus's included are influenza virus types A and B of the genus Influenzavirus, causing, respectively, influenza A and B, and influenza virus type C, which probably belongs to a separate genus and causes influenza C. (05 Mar 2000) |
| influenza virus vaccines | Influenza virus grown in embryonated eggs and inactivated, usually by the addition of formalin; both whole virus and subunit preparations containing haemagglutinins and neuraminidase are used; because of the marked and progressive antigenic variation of the influenza viruses, the strains included are regularly changed following various outbreaks of influenza in order to include most recently isolated epidemic strains of both type A influenza and type B influenza. (05 Mar 2000) |
| endemic influenza | Influenza, usually of a less severe type, occurring with some degree of regularity during the winter season, especially in the larger cities of the world. Synonym: influenza nostras. (05 Mar 2000) |