Influenza (flu)

How is influenza (flu) caused, and how is it transmitted?

The influenza virus is usually transmitted from person to person through the air. The child may catch influenza by coming into contact with viruses through the respiratory system of an infected person, if exposed to their coughing or sneezing. In addition, the virus can survive for a short period of time on objects, like door handles, pencils, telephones, mugs, and dishes.


When does an infected person transmit influenza?

In general, an index person is more contagious 24 hours after the appearance of symptoms. This is why it is difficult to control the transmission of influenza, especially in children, who often don’t know that they are sick, and thus transmit the disease. The transmission of the disease usually stops by 7 days from the beginning of the infection.


What types of influenza are there?

There are three types of influenza viruses, A, B, and C.

Types A and B are responsible for respiratory disease epidemics that occur every winter, and are related to increased rates of hospitalisation and death. Type C usually causes few, if any, symptoms, without the appearance of epidemics.

A new virus, H1N1, appeared in humans in 2009. Influenza viruses can mutate and change, thus escaping the immune system. Everyone is predisposed to catching influenza every year throughout their lifetime. This happens because if a person catches the virus during the winter one year, and develops antibodies against it, the following winter, the old antibodies become ineffective, because the virus has changed.


How serious is seasonal influenza?

Incidents are usually of mild to medium severity; however the disease may even result in death. It is estimated that in the USA every year 200 thousand people are hospitalised with complications relating to influenza, 20 thousand of whom are children under the age of 5. About 36 thousand people die every year in the USA from complications relating to seasonal influenza. Most deaths and hospitalisations concern people over 65 years old.

The H1N1 virus caused, in general, a more severe disease to people under 25 years of age, compared to the common flu.

People with risk factors such as pregnancy, asthma, diabetes, immunosupression, chronic cardiovascular or kidney diseases, face an even higher risk of serious illness.

Influenza causes significant losses in working time in adults, and school hours in children, with significant financial consequences.


What are the symptoms of influenza?

Symptoms can vary in children, but the usual symptoms are:

• Relatively high fever that rises rapidly and begins abruptly

• Muscle and joint pain, often intense, which are prominent

• Headache

• Non productive cough

• Sore throat, usually mild but not prominent

• Nausea and vomiting

• Diarrhea

• Fatigue, intense energy loss and an overwhelming feeling, which can last for weeks

• Simple congestion without evident runny nose

Symptoms in healthy children denote a worse cold than the simple cold caused by rhinoviruses.


What are the complications?

Pneumonia, otitis, dehydration may occur.


How is influenza diagnosed?

The symptoms of influenza may be similar to those of other conditions. Always visit the child’s doctor for a clinical diagnosis.

There are some rapid detection tests using saliva samples from the throat or secretions from the nose. In some cases, these are used in order to make an accurate diagnosis.


What is the treatment for influenza?

Most people recover from influenza within a week. They usually feel fatigue for up to 3 to 4 weeks.

The signs that the child needs to see a doctor urgently, or to be examined in the hospital may include:

• Difficult or rapid breathing

• Change of colour from pallor to blue or grey

• Non intake of adequate fluids

• Persistent vomiting

• Lethargy or drowsiness

• Persistent irritability

• Remission of influenza symptoms, which is followed by new fever and worsening cough


Children suffering from influenza should remain at home and avoid contact with other people until at least 24 hours after the end of fever. People with influenza should avoid their usual activities, like work, school, trips, shopping, social encounters, for as long as they are ill.

Much rest and plenty of fluids are needed. For fever or pain paracetamol may be administered. If the child is breastfeeding, he should continue to breastfeed frequently and on demand. Breastfeeding is a protective factor that reduces the risk of serious illness.

Antibiotics don’t help with influenza.

In serious cases, with hospitalisation, or when people at high risk for complications from influenza are involved, antiviral treatment may be administered (oseltamivir or zanamivir). Antivirals may make the course of the disease milder, and recovery faster. Antivirals don’t offer anything in simple influenza cases in healthy children.


How can influenza be prevented?

Good washing of the hands helps. Don’t share dishes and mugs with people who may have the virus. Teach children to cover their mouths with their hand when they cough. Exclusive breastfeeding may prevent the appearance or the serious manifestation of the disease.


How does vaccination against influenza function?

Every year, at the beginning of the season, vaccines are produced, which contain the type of the influenza type that is predicted to cause the disease during the winter that follows.
Influenza vaccines are effective and safe. In many countries like the USA they are recommended for all small children who are older than 6 months of age, before the beginning of the influenza period. In Greece the National Vaccinations Program recommends the influenza vaccine in particular to high risk groups, like children with chronic diseases or immunosupression.

Potential side effects include pain and redness at the spot of the injection, while in some cases, fever or muscle or joint pain may occur.


Stelios Papaventsis MRCPCH DCH IBCLC 2013

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