WHAT IS INFLUENZA? Influenza, commonly called "the flu," is an illness caused by RNA viruses of the family Orthomyxoviridae the influenza viruses that infect the respiratory tract of many animals, birds, and humans.
WHAT IS ORTHOMYXOVIRIDAE? The Orthomyxoviridae are a family of RNA viruses that includes five genera: Influenzavirus A, Influenzavirus B, Influenzavirus C, Isavirus and Thogotovirus. A sixth has recently been described. The first three genera contain viruses that cause influenza in vertebrates, including birds (see also avian influenza), humans, and other mammals. Isaviruses infect salmon; thogotoviruses infect vertebrates and invertebrates, such as mosquitoes and sea lice.
INFLUENZA VIRUSES ARE DIVIDED INTO THREE TYPES: Influenza A Influenza B Influenza C
INFLUENZA A Influenza A Type A viruses are divided into types based on differences in two viral surface proteins called the hemagglutinin (H) and the neuraminidase (N). Influenza type A viruses undergo two kinds of changes: Antigenic drift. Antigenic shift.
INFLUENZA A (H1N1) Influenza A (H1N1) virus is a subtype of influenza A virus and was the most common cause of human influenza (flu) in 2009. Some strains of H1N1 are endemic in humans and cause a small fraction of all influenza-like illness and a small fraction of all seasonal influenza. H1N1 (pronounced "HEE-NEE" by healthcare professionals) strains caused a few percent of all human flu infections in 2004– 2005. Other strains of H1N1 are endemic in pigs (swine influenza) and in birds (avian influenza)
In June 2009, the World Health Organization declared the new strain of swine-origin H1N1 as a pandemic. This strain is often called swine flu by the public media. This novel virus spread worldwide and had caused about 17,000 deaths by the start of 2010. On August 10, 2010, the World Health Organization declared the H1N1 influenza pandemic over, saying worldwide flu activity had returned to typical seasonal patterns
SWINE INFLUENZA Swine influenza (also called swine flu, or pig flu) is an infection by any one of several types of swine influenza virus. Swine influenza virus (SIV) is any strain of the influenza family of viruses that is endemic in pigs. As of 2009, the known SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H3N1, H3N2, and H2N3. Swine influenza virus is common throughout pig populations worldwide. Transmission of the virus from pigs to humans is not common and does not always lead to human influenza, often resulting only in the production of antibodies in the blood. If transmission does cause human influenza, it is called zoonotic swine flu. People with regular exposure to pigs are at increased risk of swine flu infection. The meat of an infected animal poses no risk of infection when properly cooked. Pigs experimentally infected with the strain of swine flu that is causing the current human pandemic showed clinical signs of flu within four days, and the virus spread to other uninfected pigs housed with the infected ones.
AVIAN INFLUENZA Avian influenza — known informally as avian flu or bird flu — refers to "influenza caused by viruses adapted to birds."Of the greatest concern is highly pathogenic avian influenza (HPAI). "Bird flu" is a phrase similar to "swine flu," "dog flu," "horse flu," or "human flu" in that it refers to an illness caused by any of many different strains of influenza viruses that have adapted to a specific host. All known viruses that cause influenza in birds belong to the species influenza A virus. All subtypes (but not all strains of all subtypes) of influenza A virus are adapted to birds, which is why for many purposes avian flu virus is the influenza A virus. (Note, however, that the "A" does not stand for "avian").
THE FLU PANDEMIC In the 2009 flu pandemic, the virus isolated from patients in the United States was found to be made up of genetic elements from four different flu viruses – North American swine influenza, North American avian influenza, human influenza, and swine influenza virus typically found in Asia and Europe – "an unusually mongrelised mix of genetic sequences." This new strain appears to be a result of reassortment of human influenza and swine influenza viruses, in all four different strains of subtype H1N1. Preliminary genetic characterization found that the hemagglutinin (HA) gene was similar to that of swine flu viruses present in U.S. pigs since 1999, but the neuraminidase (NA) and matrix protein (M) genes resembled versions present in European swine flu isolates. The six genes from American swine flu are themselves mixtures of swine flu, bird flu, and human flu viruses. While viruses with this genetic makeup had not previously been found to be circulating in humans or pigs, there is no formal national surveillance system to determine what viruses are circulating in pigs in the U.S
INFLUENZA B Influenza type B viruses change only by the more gradual process of antigenic drift.
INFLUENZA C Type C infection usually causes either a very mild respiratory illness or no symptoms at all;
SIGNS AND SYMPTOMS Fever (usually 100 F-103 F in adults and often even higher in children) Cough, Sore throat, Runny or stuffy nose, Headache, Muscle aches, Extreme fatigue
MODE OF TRANSMISSION Influenza is spread mainly from person to person by droplet infection or droplet nuclei created by sneezing, coughing or talking. The portal of entry of the virus is the respiratory tract.
DIAGNOSIS Virus Isolation Nasopharyngeal secretions are the best specimens for obtaining large quantities of virus–infected cells. Paired Sera A sero diagnosis of influenza A or B can be made by the examination of two serum specimens from a patient.
PREVENTIONVaccine: The ―flu shot‖ — an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The nasal-spray flu vaccine — a vaccine made with live, weakened flu viruses that is given as a nasal spray (sometimes called LAIV for ―Live Attenuated Influenza Vaccine‖).
MEDICATIONS Increasing liquid intake, warm showers, and warm compresses, especially in the nasal area, can reduce the body aches and reduce nasal congestion. Nasal strips and humidifiers may help reduce congestion, especially while trying to sleep. Fever can be treated with over-the counter acetaminophen (Tylenol) or ibuprofen (Motrin and others)