Severe Acute Respiratory Syndrome (SARS; pronounced /sɑrz/, sarz) is a respiratory disease in humans which is caused by the SARS coronavirus (SARS-CoV). There has been one near pandemic to date, between the months of November 2002 and July 2003, with 8,096 known infected cases and 774 deaths (a case-fatality rate of 9.6%) worldwide being listed in the World Health Organization's (WHO) 21 April 2004 concluding report. Within a matter of weeks in early 2003, SARS spread from the Guangdong province of China to rapidly infect individuals in some 37 countries around the world.
Mortality by age group as of 8 May 2003 is below 1 percent for people aged 24 or younger, 6 percent for those 25 to 44, 15 percent in those 45 to 64 and more than 50 percent for those over 65.[4] For comparison, the case fatality rate for influenza is usually around 0.6 percent (primarily among the elderly) but can rise as high as 33 percent in locally severe epidemics of new strains. The mortality rate of the primary viral pneumonia form is about 70 percent
Wednesday, May 13, 2009
Influenza virus
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses), that affects birds and mammals. The name influenza comes from the Italian influenza, meaning "influence" (Latin: influentia). The most common symptoms of the disease are chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. Fever and coughs are the most frequent symptoms. In more serious cases, influenza causes pneumonia, which can be fatal, particularly for the young and the elderly. Although it is often confused with other influenza-like illnesses, especially the common cold, influenza is a much more severe disease than the common cold and is caused by a different type of virus. Influenza may produce nausea and vomiting, particularly in children,but these symptoms are more common in the unrelated gastroenteritis, which is sometimes called "stomach flu" or "24-hour flu".
Typically, influenza is transmitted through the air by coughs or sneezes, creating aerosols containing the virus. Influenza can also be transmitted by bird droppings, saliva, nasal secretions, feces and blood. Infections also occur through contact with these body fluids or with contaminated surfaces. Airborne aerosols have been thought to cause most infections, although which means of transmission is most important is not absolutely clear. Influenza viruses can be inactivated by sunlight, disinfectants and detergents.As the virus can be inactivated by soap, frequent hand washing reduces the risk of infection.
Typically, influenza is transmitted through the air by coughs or sneezes, creating aerosols containing the virus. Influenza can also be transmitted by bird droppings, saliva, nasal secretions, feces and blood. Infections also occur through contact with these body fluids or with contaminated surfaces. Airborne aerosols have been thought to cause most infections, although which means of transmission is most important is not absolutely clear. Influenza viruses can be inactivated by sunlight, disinfectants and detergents.As the virus can be inactivated by soap, frequent hand washing reduces the risk of infection.
Types of Virus
Viral
Further information: Table of clinically important viruses
Pathogenic viruses are mainly those of the families of: Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Rhabdoviridae, Togaviridae. Some notable pathogenic viruses cause: smallpox, influenza, mumps, measles, chickenpox and rubella. Ebola is another pathogenic virus. Viruses typically range from between 20-300 nanometers in length.
Bacterial
Main article: Pathogenic bacteria
Although the vast majority of bacteria are harmless or beneficial, a few pathogenic bacteria can cause infectious diseases. The most common bacterial disease is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which effect about 2 million people mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis and leprosy. Bacteria can often be killed by antibiotics. They typically range from between 1-5 micrometers in length.
Fungal
Fungal microbes can cause diseases in humans, animals and crop plants. Fungi most often infect immuno-compromised patients or vulnerable people with a weakend immune system. Most antibiotics cannot be used to treat fungal infections due to the fact that fungi and their hosts both have eukaryotic cells. Most clinical fungicides belong to the azole group. The typical fungal spore size is 1-40 micrometer in length. It's a death promblem
Further information: Table of clinically important viruses
Pathogenic viruses are mainly those of the families of: Adenoviridae, Picornaviridae, Herpesviridae, Hepadnaviridae, Flaviviridae, Retroviridae, Orthomyxoviridae, Paramyxoviridae, Papovaviridae, Rhabdoviridae, Togaviridae. Some notable pathogenic viruses cause: smallpox, influenza, mumps, measles, chickenpox and rubella. Ebola is another pathogenic virus. Viruses typically range from between 20-300 nanometers in length.
Bacterial
Main article: Pathogenic bacteria
Although the vast majority of bacteria are harmless or beneficial, a few pathogenic bacteria can cause infectious diseases. The most common bacterial disease is tuberculosis, caused by the bacterium Mycobacterium tuberculosis, which effect about 2 million people mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Streptococcus and Pseudomonas, and foodborne illnesses, which can be caused by bacteria such as Shigella, Campylobacter and Salmonella. Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis and leprosy. Bacteria can often be killed by antibiotics. They typically range from between 1-5 micrometers in length.
Fungal
Fungal microbes can cause diseases in humans, animals and crop plants. Fungi most often infect immuno-compromised patients or vulnerable people with a weakend immune system. Most antibiotics cannot be used to treat fungal infections due to the fact that fungi and their hosts both have eukaryotic cells. Most clinical fungicides belong to the azole group. The typical fungal spore size is 1-40 micrometer in length. It's a death promblem
Pathogenic virus
A pathogen (from Greek πάθος path "suffering, passion", and γἰγνομαι (γεν-) gignomai (gen-) "I give birth to"), infectious agent, or (more commonly) germ, is a biological agent that causes disease or illness to its host There are several substrates and pathways whereby pathogens can invade a host; the principal pathways have different episodic time frames, but soil contamination has the longest or most persistent potential for harboring a pathogen.
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