The term influenza has its origins in 15th-century Italy, where the cause of the disease was ascribed to unfavourable astrological influences. Evolution in medical thought led to its modification to influenza del freddo, meaning “influence of the cold.” The word “influenza” was first attested in English in 1743 when it was borrowed during an outbreak of the disease in Europe. Archaic terms for influenza include epidemic catarrh, grippe (from the French grippe, meaning flu; sometimes spelled “grip” or “gripe”), sweating sickness, and Spanish fever (particularly for the 1918 pandemic strain).
It is an infectious disease of birds and mammals caused by RNA viruses of the family Orthomyxoviridae (the influenza viruses). In humans, common symptoms of influenza infection are fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort. In more serious cases, influenza causes pneumonia, which can be fatal, particularly in young children and the elderly. Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus. Although nausea and vomiting can be produced, especially in children, these symptoms are more characteristic of the unrelated gastroenteritis, which is sometimes called “stomach flu” or “24-hour flu.”
Typically, influenza is transmitted from infected mammals through the air by coughs or sneezes, creating aerosols containing the virus, and from infected birds through their droppings. Influenza can also be transmitted by saliva, nasal secretions, feces and blood. Infections also occur through contact with these body fluids or with contaminated surfaces.
Flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 Â°C (32 Â°F), and indefinitely at very low temperatures (such as lakes in northeast Siberia). Most influenza strains can be inactivated easily by disinfectants and detergents.
Flu spreads around the world in seasonal epidemics, killing millions of people in pandemic years and hundreds of thousands in non-pandemic years. Three influenza pandemics occurred in the 20th century and killed tens of millions of people, with each of these pandemics being caused by the appearance of a new strain of the virus in humans. Often, these new strains result from the spread of an existing flu virus to humans from other animal species.
Since it first killed humans in Asia in the 1990s, a deadly avian strain named H5N1 has posed the greatest risk for a new influenza pandemic; fortunately, this virus has not mutated to a form that spreads easily between people.
Vaccinations against influenza are most commonly given to high-risk humans in industrialized countries and to farmed poultry. The most common human vaccine is the trivalent flu vaccine that contains purified and inactivated material from three viral strains. Typically this vaccine includes material from two influenza A virus subtypes and one influenza B virus strain. A vaccine formulated for one year may be ineffective in the following year, since the influenza virus changes rapidly over time and different strains become dominant. Antiviral drugs can be used to treat influenza, with neuraminidase inhibitors being particularly effective.
The flu usually begins abruptly, with a fever between 102 to 106Â°F. (An adult typically has a lower fever than a child.) Other common symptoms include a flushed face, body aches, and lack of energy. Some people have dizziness or vomiting. The fever usually lasts for a day or two, but can last 5 days.
Somewhere between day 2 and day 4 of the illness, the “whole body” symptoms begin to subside, and respiratory symptoms begin to increase. The flu virus can settle anywhere in the respiratory tract, producing symptoms of a cold, croup, sore throat, bronchiolitis, ear infection, or pneumonia.
The most prominent of the respiratory symptoms is usually a dry, hacking cough. Most people also develop a sore throat and headache. Nasal discharge (runny nose) and sneezing are common. These symptoms (except the cough) usually disappear within 4-7 days. Sometimes, the fever returns. Cough and tiredness usually last for weeks after the rest of the illness is over.
The flu usually arrives in the winter months. The most common way to catch the flu is by breathing in droplets from coughs or sneezes. Less often, it is spread when you touch a surface such as a faucet handle or phone that has the virus on it, and then touch your own mouth, nose, or eyes.
Symptoms appear 1-7 days later (usually within 2-3 days). Because the flu spreads through the air and is very contagious, it often strikes a community all at once. This creates a cluster of school and work absences. Many students become sick within 2 or 3 weeks of the flu’s arrival in a school.
Tens of millions of people in the United States get the flu each year. Most get better within a week or two, but thousands become sick enough to be hospitalized. About 36,000 people died each year from complications of the flu.
Anyone at any age can have serious complications from the flu, but those at highest risk include:
People over 50
Children between 6 months and 2 years
Women more than 3 months pregnant during the flu season
Anyone living in a long-term care facility
Anyone with chronic heart, lung, or kidney conditions, diabetes, or weakened immune system
Sometimes people confuse cold and flu, which share some of the same symptoms and typically occur at the same time of the year. However, the two diseases are very different. Most people get a cold several times each year, and the flu only once every several years.
People often use the term “stomach flu” to describe a viral illness where vomiting or diarrhea are the main symptoms. This is incorrect, as the stomach symptoms are not caused by the flu virus. Flu infections are primarily respiratory infections.
In humans, influenza’s effects are much more severe than those of the common cold, and last longer. Recovery takes about one to two weeks. Influenza, however, can be deadly, especially for the weak, old or chronically ill.
Fever – may be high
Stuffy, congested nose
Muscle aches and stiffness
Other symptoms may include:
Shortness of breath
Loss of appetite
Worsening of underlying illnagnosis:ess, such as asthma or heart failure.
Most people who get influenza will recover in one to two weeks, but others will develop life-threatening complications (such as pneumonia). According to the World Health Organization: “Every winter, tens of millions of people get the flu. Most are home, sick and miserable, for about a week. Some ”mostly the elderly die. We know the world-wide death toll exceeds a few hundred thousand people a year, but even in developed countries the numbers are uncertain, because medical authorities don’t usually verify who actually died of influenza and who died of a flu-like illness.” Even healthy people can be affected, and serious problems from influenza can happen at any age. People over 50 years old, very young children and people of any age with chronic medical conditions, are more likely to get complications from influenza: such as pneumonia, bronchitis, sinus, and ear infections.
The flu can worsen chronic health problems. People with emphysema, chronic bronchitis or asthma may experience shortness of breath while they have the flu, and influenza may cause worsening of coronary heart disease or congestive heart failure. Smoking is another risk factor associated with more serious disease and increased mortality from influenza
The evaluation of an individual with flu symptoms should include a thorough physical exam and, in cases where pneumonia is suspected, a chest x-ray.
Additional blood work may be needed. They may include a complete blood count, blood cultures, and sputum cultures.
The most common method for diagnosing the flu is an antigen detection test, which is done by swabbing the nose and throat, then sending a sample to the laboratory for testing.
The results of these tests can be available rapidly, and can help decide if specific treatment is appropriate. However, the diagnosis can often be made by simply identifying symptoms without further testing.
If you have mild illness and are not at high-risk, take these steps:
Take medicines that relieve symptoms and help you rest
Drink plenty of liquids
Avoid aspirin (especially teens and children)
Avoid alcohol and tobacco
Avoid antibiotics (unless necessary for another illness)
If the flu is diagnosed within 48 hours of when symptoms begin, especially if you are high risk for complications, antiviral medications may help shorten the length of symptoms by approximately a day.
In the past, doctors commonly prescribed the antiviral medications amantadine and rimantadine to treat type A influenza. The U.S. Centers for Disease Control and Prevention now recommends that neither drug be used for such treatment because of growing resistance to the drugs. Instead, the agency recommends using oseltamivir (Tamiflu) or zanamivir (Relenza), which are active against both influenza A and B. Each of these medicines has different side effects and affects different viruses. Your doctor will determine which one is best for you.
Treatment is usually not necessary for children, but if the illness is diagnosed early and the patient is at risk of developing a severe case, it can be started. Oseltamivir (Tamiflu) is the best choice for children age 12 and older. It is available in as a liquid, which may make it easier to give to the child than zanamivir (Relenza), which comes in an inhaler.
Treatment will only help if started early and only if the illness is actually influenza. It will not help treat a regular cold.
Prognosis:In most individuals who are otherwise healthy, the flu goes away within 7 to 10 days.
Possible Complications :
Possible complications, especially for those at high risk, include:
Encephalitis (infection of the brain)
A yearly vaccine is recommended for infants, the elderly, women who may be pregnant during flu season, and those with certain chronic health conditions. The vaccine is also recommended for people who work or live with others at high risk.
A flu shot can help lower one’s chances of getting the flu. A flu shot is generally available to people who:
Are over 6 months old
Don’t have a serious allergy to eggs
Haven’t had a serious reaction to flu shots in the past
Are not pregnant
A new nasal spray-type flu vaccine called FluMist is available to people aged 2 to 49 years old. FluMist uses a live, weakened virus instead of a dead one like the flu shot. In one study, the nasal spray provided protection against the flu in up to 93% of children.
Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose