Various Forms Of Influenza Viruses

by Vinay Choubey

Influenza, commonly known as the flu, is an infectious disease of birds and mammals caused by an RNA virus of the family Orthomyxoviridae (the influenza viruses). In people, common symptoms are fever, sore throat, muscle pains, severe headache, coughing, and weakness and fatigue. 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 caused by a different type of virus. Similarly, the unrelated gastroenteritis is sometimes called "stomach flu" or "24-hour flu".

Types of influenza virus

The influenza virus is an RNA virus of the family Orthomyxoviridae, which comprises the influenzaviruses, Isavirus and Thogotovirus. There are three types of influenza virus: Influenzavirus A, Influenzavirus B or Influenzavirus C. Influenza A and C infect multiple species, while influenza B almost exclusively infects humans.

The type A viruses are the most virulent human pathogens among the three influenza types and cause the most severe disease. The Influenza A virus can be subdivided into different serotypes based on the antibody response to these viruses.

Influenza B virus is almost exclusively a human pathogen, and is less common than influenza A. The only other animal known to be susceptible to influenza B infection is the seal. This type of influenza mutates at a rate 2-3 times lower than type A and consequently is less genetically diverse, with only one influenza B serotype. As a result of this lack of antigenic diversity, a degree of immunity to influenza B is usually acquired at an early age.

The influenza C virus infects humans and pigs, and can cause severe illness and local epidemics. However, influenza C is less common than the other types and usually seems to cause mild disease in children.

PATHOGENESIS AND DISEASE

Spread

The virus is spread person to person via small particle aerosols (less than 10ìm diameter) that can get into respiratory tract. It can also survive for a short time on surfaces and can be spread by this route if the virus is introduced into the nasal mucosa before it loses infectivity. The incubation period is short, about 18 to 72 hours.

Virus concentration in nasal and tracheal secretions remains high for 24 to 48 hours after symptoms start and may last longer in children. Titers are usually high and so there are enough infectious virions in a small droplet to start a new infection.

Site of infectiion

Influenza virus infects the epithelial cells of the respiratory tract. The cells die, in part due to the direct effects of the virus on the cell, and also possibly due to the effects of interferon. Cell death at later times may also result from the actions of cytotoxic T-cells. As a result, the efficiency of ciliary clearance is reduced, leading to impaired function of the mucus elevator; thus there is reduced clearance of infectious agents from the respiratory tract. Gaps in the protective epithelium provide other pathogens with access to other cells; however, viremia is very rare.

Recovery

Interferon may play a role by decreasing virus production. Many of the symptoms of uncomplicated influenza (muscle aches, fatigue, fever) are associated with the efficient induction of interferon. The cell-mediated immune response is important in viral clearance. The antibody response is usually not significant until after virus has been cleared. Repair of the respiratory epithelium begins rapidly, but may take some time to complete.

About the Author
Vinay Choubey SEO Manager For more details on Influenza Viruses visit us at http://www.halfvalue.com and http://www.halfvalue.co.uk For information on Books Visit: http://www.lookbookstores.com

Cold and Flu - Causes, Symptoms, Treatment

by James Sameul

What is Cold and Flu
Is it a cold or the flu? While a common cold, including chest cold and head cold, can be caused by more than 200 viruses, seasonal flu is caused by either influenza A or B viruses. Cold and flu remedies can usually ease symptoms. Antiviral medications like Relenza or Tamiflu are helpful if prescribed soon after flu symptoms start.Influenza (commonly known as the flu) and colds are among the most common infections of the respiratory system. People often confuse the two, calling a bad cold the "flu," or vice versa.

Typically, the flu (also known as influenza) has symptoms that make a child feel worse than symptoms associated with a common cold, but it's not always that easy to tell the difference between the two.

What are the causes of the flu? Influenza viruses are divided into three types, designated A, B, and C. Influenza types A and B are responsible for epidemics of respiratory illness that occur almost every winter and are often associated with increased rates of hospitalization and death. Influenza type C differs from types A and B in some important ways.

The truth is, the flu and the common cold are caused by viruses. People get sick more often in the winter because they are exposed to each other more in the winter than in the summer. When it is cold outside, people tend to stay inside and are more likely to spread germs to one another.

The flu is caused by three types (strains) of viruses -- influenza A, B and C. Type A is responsible for the deadly influenza pandemics (worldwide epidemics) that strike every 10 to 40 years. Type B can lead to smaller, more localized outbreaks. And either types A or B can cause the flu that circulates almost every winter. Type C has never been connected with a large epidemic.

Symptoms of Cold and Flu Viral pharyngitis may develop gradually. It is often accompanied by the flu or a cold, and body aches. If a fever is present, it will generally be in the range of 101 degrees F or below.With cold symptoms, your nose teems with watery nasal secretions for the first few days. Later, these become thicker and darker. Dark mucus is natural and does not usually mean you have developed a bacterial infection, such as a sinus infection.

Recognizing the symptoms of the common cold is important for a few reasons. If you realize what symptoms are bothering you the most, you will know which medications will help relieve them.

Introduction to cold, flu, and allergy treatments Every year, millions of people use over-the-counter (OTC) products to relieve nasal stuffiness and congestion, sneezing, runny noses, sore throat, and cough. The common causes of these symptoms include the viruses that cause the common cold, influenza virus, allergic rhinitis (hay fever), and sinus infections (sinusitis).

ince it is caused by a virus, antibiotics do not work against the common cold. These types of upper respiratory infections go away on their own and taking antibiotics will not help your child get better any faster and will likely not prevent secondary bacterial infections, such as an ear infection or sinus infection.

For thick phlegm, patients may try cough medications that contain guaifenesin (Robitussin, Scot-Tussin Expectorant), which loosens mucus. Patients should not suppress coughs that produce mucus and phlegm; it is important to expel this substance. To loosen phlegm, patients should drink plenty of fluids and use a humidifier or steamer.Take paracetamol to control fever, aches and pains (adults can use aspirin). Early use of antiviral medication may shorten the length and severity of illness. Consult a doctor to discuss treatment.


About the Author
Read about Home Remedies. Also Read about Health Blog, Fitness Blog and Herbal Remedies, Natural Remedies