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Influenza

Influenza (Flu)

What is influenza?

Influenza (or flu) is a highly contagious viral infection and is one of the most severe illnesses of the winter season. An estimated 10 to 20 percent of the population in the US contract influenza each year.

Influenza is a viral infection of the upper respiratory system, which includes the nose, bronchial tubes, and lungs. Influenza is characterized by the following:

Influenza can make people of any age ill. Although most people and children are ill with influenza for only a few days, some have a much more serious illness and may need to be hospitalized. Influenza may also lead to pneumonia and/or death.

What are the different types of influenza?

Influenza viruses are divided into three types designated as A, B, and C.

Influenza viruses continually mutate or change, which enables the virus to evade the immune system of a child. People are susceptible to influenza infection throughout their lives. The process works as follows:

  1. A person infected with influenza virus develops antibody against that virus.
  2. The virus mutates or changes.
  3. The "older" antibody no longer recognizes the "newer" virus.
  4. Reinfection occurs.

The older antibody can, however, provide partial protection against reinfection. Currently, three different influenza strains circulate worldwide: two type A viruses and one type B. Type A viruses are divided into subtypes based on differences in two viral proteins called hemagglutinin (H) and neuraminidase (N). The current subtypes of influenza A are designated A(H1N1), A(H3N2), and B(Hong Kong/330/2001-like virus strain).

What causes influenza?

An influenza virus is generally passed from person to person by airborne transmission. This means your child can contract the flu by coming in contact with airborne viruses from an affected person by way of sneezing and coughing. The virus can also live for a short time on objects such as doorknobs, pens/pencils, keyboards, telephone receivers, and eating or drinking utensils, for example. Therefore, it may also be spread when your child touches something that has been handled by someone infected with the virus and then your child touches his/her own mouth, nose, or eyes.

People are generally the most contagious with the flu 24 hours before they start having symptoms and during the time they have the most symptoms. That is why it is hard to prevent the spread of the flu, especially among children, because they do not always know they are sick while they are still spreading the disease. The risk of infecting others usually stops around the seventh day of the infection.

What are the symptoms of influenza?

The following are the most common symptoms of the flu. However, each child may experience symptoms differently.

Influenza is called a respiratory disease, but the whole body seems to suffer when a child has it. Children usually become suddenly ill with any or all of the following symptoms:

Most people recover from influenza within a week, but may be left feeling exhausted for as long as three to four weeks.

The symptoms of influenza may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

How is a cold different from the flu?

A cold and the flu (influenza) are two different illnesses. A cold is relatively harmless and usually clears up by itself after a period of time, although sometimes it may lead to a secondary infection, such as an ear infection. However, the flu can lead to complications, such as pneumonia and even death. What may seem like a cold, could, in fact, be the flu. Be aware of these differences:

Cold Symptoms Flu Symptoms
Low or no fever High fever
Sometimes a headache Always a headache
Stuffy, runny nose Clear nose or stuffy nose
Sneezing Sometimes sneezing
Mild, hacking cough Cough, often becoming severe
Slight aches and pains Often severe aches and pains
Mild fatigue Several weeks of fatigue
Sore throat Sometimes a sore throat
Normal energy level Extreme exhaustion

Prevention of influenza:

A new influenza vaccine is introduced each September. It is usually recommended for specific groups of people (see below), as well as for persons who want to avoid having the flu. In addition, three antiviral medications (amantadine, rimantadine, and oseltamivir) are approved for use in preventing the flu. All of these medications are available by prescription, and a physician should be consulted before any medication is used for preventing the flu.

A nasal-spray flu vaccine, called FluMist, is currently approved to prevent flu due to influenza A and B viruses in healthy children and adolescents (ages five to 17), and healthy adults (ages 18 to 49). As with other live virus vaccines, FluMist should not be given for any reason to people with immune suppression, including those with immune deficiency diseases, such as AIDS or cancer, and people who are being treated with medications that cause immunosuppression.

Vaccine effectiveness:

According to the American Lung Association, an influenza vaccination is about 70 percent effective in preventing influenza, or reducing its severity, and is considered safe.

However, vaccine effectiveness varies from year to year, depending upon the degree of similarity between the influenza virus strains included in the vaccine and the strain or strains that circulate during the influenza season. Vaccine strains must be chosen nine to ten months before the influenza season. Sometimes, changes occur in the circulating strains of viruses between the time vaccine strains are chosen and the next influenza season. These changes may reduce the ability of the vaccine-induced-antibody to inhibit the newly mutated virus, thereby decreasing the chance that the vaccine will work.

Vaccine effectiveness also varies from one person to another, depending on factors such as age and overall health.

What are the side effects of the vaccine?

The most serious side effect that can occur after influenza vaccination is an allergic reaction in people who have a severe allergy to eggs. For this reason, children who have an allergy to eggs should not receive the influenza vaccine. According to the National Center for Infectious Diseases of the Centers for Disease Control and Prevention (CDC), influenza vaccine causes no side effects in most children who are not allergic to eggs.

Less than one-third of people who receive the vaccine experience some soreness at the vaccination site, and about 5 to 10 percent experience mild side effects, such as a headache or a low-grade fever for about a day after vaccination. Because these mild side effects mimic some influenza symptoms, some people believe influenza vaccine causes them to get influenza. However, according to the CDC, "influenza vaccine produced in the United States has never been capable of causing influenza because the only type of influenza vaccine that has been licensed in the United States to the present time is made from killed influenza viruses, which cannot cause infection."

Vaccine recommendations:

The recommendations for those who should have the influenza vaccine include the following:

In addition, the following groups should be vaccinated:

Treatment for influenza:

Specific treatment for influenza will be determined by your child's physician based on:

The goal of treatment for influenza is to help prevent or decrease the severity of symptoms. There is no cure for influenza. Treatment may include:

Click here to view the
Online Resources of Infectious Diseases


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