What is the flu?
Influenza, or influenza, is a disease caused by influenzae viruses of the family Orthomyxoviridae, an RNA virus. Contagious disease, influenza first affects the respiratory system and can be complicated or present serious forms.
How long does the flu last?
It usually lasts from 3 to 7 days and can prevent a person from carrying out his daily activities.
The different flu viruses
There are 3 types of influenza viruses , with different subtypes classified according to their surface glycoproteins, neuraminidases and hemagglutinins :
Influenza Type A
This is the most dangerous. It caused several deadly pandemics like the famous Spanish flu of 1918, which killed more than 20 million people. In 1968, it was the turn of the “Hong Kong flu” to trigger a pandemic. Type A is transformed in a very short time, which makes it all the more difficult to fight. Indeed, the body must build an immune response specific to each new influenza strain in circulation.
Type A virus causes a pandemic about 3 or 4 times a century. In 2009, a new type A virus , H1N1 , triggered another pandemic. According to public health authorities, the virulence of this pandemic has been “moderate” in terms of the number of deaths. For more information, check out our A flu (H1N1) file.
Bird flu is also a type A virus that affects birds, whether they are slaughtered (chickens, turkeys, quails), wild birds (geese, ducks) or domestic birds. The virus is easily transmitted from birds to humans, but rarely between humans. The H5N1 strainhas caused several deaths in Asia, usually in people who have close contact with sick or dead poultry or who have frequented live poultry markets.
The influenza of Type B
Most often, its manifestations are less serious. It only leads to localized epidemics. This type of flu is less subject to mutations than type A.
Type C Influenza
The symptoms it provokes are similar to those of a common cold. This type of flu is also less subject to mutations than Type A.
Do viruses evolve?
This type of virus constantly undergoes genetic modifications (genotypic modifications). That’s why having a flu one year does not provide immunity against the viruses that will circulate the following years. You can get a new flu each year. Vaccines must be adapted every year to protect the population against new variants of the virus.
Influenza and contagion: how long does it last?
An infected person can be contagious the day before his first symptoms and can spread the virus for 5 to 10 days. Children are sometimes contagious for more than 10 days .
The incubation lasts 1 to 3 days , which means that when one is infected with the influenza virus, the signs can start to appear from 1 day after the infection until 3 days later.
The flu, how does it get caught?
Influenza spreads easily , by contagion and especially by contaminated microdroplets that are released into the air when coughing or sneezing. The virus can also be transmitted by saliva. Since the virus can be quickly found on the face and hands of a stuck person, kisses and handshakes to sick people should be avoided.
Transmission is more rarely done by saliva-affected objects or contaminated droplets; the virus persists on the hands for 5 to 30 minutes and in the stool several days . On inert surfaces, the virus remains active for several hours, so avoid touching objects of the patient (toys, table, cutlery, and toothbrush).
Flu or cold, what differences?
In case of colds :
To find out more, read our Cold sheet.
Does the flu get caught more easily when it’s cold?
The Italians of the XIV century believed that contagion episodes flu were brought by the cold . They had named it influenza di fredo . They were not entirely wrong, because in the temperate zones of the northern and southern hemispheres, the flu is more common in winter. But at the time, they were probably unaware that in the tropical zone, outbreaks of influenza can occur at any time of the year (there is no flu season!).
For a long time it was thought that “getting cold” reduced the body’s resistance to the flu and colds. However, there is no indication that cold weakens the immune system or facilitates the entry of the virus into the respiratory tract.
If the flu is more common in winter, it seems more likely that it is due to confinement inside houses , which promotes contagion . In addition, the fact that the air is drier in winter also facilitates contagion, because the mucous membranes of the nose dry up. Indeed, the mucous membranes prevent the entry of microbes more effectively when they are wet. In addition, dry air of winter facilitate the survival of the virus outside the body.
Possible complications of the flu
- Bacterial infection: complications can arise if the flu (viral infection) adds a bacterial infection otitis media , a sinusitis , a pneumonia post influenzae bacterial occurring from 4 th to 14 th day after the start of infection, more often in the elderly.
- Pneumonia corresponding to a primary malignant flu. Rare and serious, it leads to hospitalization in medical resuscitation.
- Complications affecting other organs than the lungs, such as myocarditis (inflammation of the heart muscle), pericarditis (inflammation of the pericardium, membrane around the heart, encephalitis (inflammation of the brain), rhabdmyolysis (severe muscle damage), Reye’s syndrome ( when taking aspirin in children, causing acute hepatitis and encephalitis, very serious).
- Complications in people with impaired immunity,
- During pregnancy, miscarriage, prematurity, neurological congenital malformations.
- And in the elderly, pre-existing cardiac , respiratory or renal insufficiency which can worsen considerably (decompensation).
Individuals with weaker health, such as the elderly, immunocompromised and those with lung disease , are at higher risk for complications and death.
When to consult a doctor ?
In the presence of the following symptoms, it is best to consult a doctor to detect and possibly treat the complications that may occur.
- A fever of more than 38.5 ° C for more than 72 hours.
- From shortness of breath to rest.
- Chest pain.
How many people get the flu each year?
In metropolitan France , every year, during an influenza epidemic, between 788,000 and 4.6 million people consult their general practitioner, which means an average of 2.5 million people affected each year by influenza. And nearly 50% of them are under 18 years old. During the 2014-2015 influenza outbreak, there were 1600 cases of severe influenza and 280 deaths. But the excess mortality related to influenza was then estimated at 18,300 deaths (mortality among frail people who without the flu probably would not have died).
Influenza affects every year by 10% to 25% of the population Canada. The vast majority of infected people recover without difficulty. All the same, influenza is involved in 3000 to 5000 deaths in Canada, usually among people already weakened.
When does the flu get caught?
In North America, as in Europe, the flu season runs from November to April. The seasonal incidence of influenza varies according to the latitude of the country where you are and the annual virus in circulation.
Symptoms of the flu
The symptoms can last from 24 hours to 1 week or more, but usually they occur for 3 to 7 days. Most often, the temperature decreases in 2 to 4 days. Fatigue and coughing can persist for up to 2 weeks, and sometimes longer.
Symptoms of influenza in adults
- The invasion phase with an appearance of chills, malaise, sudden fever above 39 °, muscle pain, headache ,
- Then the flu phase can be manifested by the following signs that are present in a variable way depending on the person affected:
- high fever , up to 40 °, although in children under 5 years and over 65 years, the fever may not be very important.
- accelerated heart rate ( tachycardia )
- fatigue, abatement that can cause drowsiness,
- lack of appetite (anorexia),
- runny nose (rhinorrhea),
- sore throat,
- difficulty swallowing ( dysphagia) ,
- veiled voice, difficulty speaking,
- burns in the chest,
- dry cough,
- severe headaches in the forehead, eyes,
- difficulty with light ( photophobia )
- Influenza can be seen by some people as extra-respiratory , with signs of other organs, which may suggest that it is another disease. These signs are:
- digestive disorders (sometimes for example viral gastroenteritis or intestinal flu),
- signs of meningitis (inflammation of the meninges, envelopes of the brain),
- signs of encephalitis (inflammation of the brain, the brain),
- signs of pericarditis (inflammation of the heart’s envelope, the pericardium),
- myocarditis (inflammation of the heart muscle),
- myositis (inflammation of the muscles).
- Other possible manifestations: a burning sensation in the eyes, night sweats, viral gastroenteritis(this is called intestinal flu, common in children), marked drowsiness, loss of appetite and joint pain.
|The so-called flu-like illness (basic flu-like symptoms) may be caused by other viruses, such as para-influenza or respiratory syncytial virus, or a sign of another disease.|
In children, how does the flu manifest itself?
In children, influenza can occur differently.
Sometimes before a year , there is almost no symptom, or on the contrary a very serious flu can occur.
Before 3 years and up to 5 years , there is often somnolence (about one in two cases), disorders of consciousness, digestive disorders, or a simple fever with no other associated sign.
Younger children are at risk especially children under 6 months of age, or to a lesser extent less than 2 years old.
People at risk and risk factors for influenza
Who gets flu more easily?
Everyone can get the flu. Some people, whose immunity is lower, are at higher risk.
- Very young children , especially those who go to kindergarten, daycare or nursery, as well as people who are in contact with them.
- Older people , especially if they live in retirement homes, rest homes or reception centers. It is in this group that we find 80% to 90% of deaths caused by influenza.
- Health workers , because of frequent contact with risk groups.
- Pregnant women
- People suffering from obesity,
- People with chronic illness , such as HIV-AIDS , kidney disease, liver disease, cardiovascular or pulmonary disease, severe anemia, severe chronic neurological disease, or diabetes.
What are the risk factors for influenza?
- Have a weakened immune system due to chronic stress, lack of sleep, poor nutrition, etc.
- Frequent public places during periods of epidemic (markets, public transport, public toilets, etc.).
- Share a restricted space with several people, for example traveling by train, plane or on cruise ships.
- Visit a sick person with the flu.
Prevention of the flu
Influenza usually does not have serious health consequences. However, when it occurs in people with fragile health, the infection can lead to serious, potentially life-threatening complications.
How to avoid flu contagion?
- Wash your hands often
Avoid touching your eyes, mouth or nose, which are the gateway to the virus. See the diagram above.
- Do not get too close to an infected person to avoid contagion. The virus travels through microdroplets thrown into the air by sneezing and coughing. So you have to protect yourself accordingly. If you have the flu, you have to cough in the crook of your elbow.
- Less frequent public places.
- Get vaccinated if possible before the epidemic period or at the very beginning if you have not done so if you are at risk or if you are exposed to risk factors.
- Remember that people with seizures remain contagious as long as their symptoms persist.
For people living in an institution (care establishment, retirement home, hospital), the patient must wear a surgical mask if he can bear it. (As a family, this can also be done!)
Strengthen immunity against the flu
During the flu season, almost all people are exposed to the virus, but only some people get the flu. It depends on the immune response of everyone. The immune system can be strengthened through certain measures:
- Have a healthy diet . To learn more about eating habits that help prevent the flu, see our Flu, Colds and Feeds in 10 Questions.
- Reduce consumption of alcohol, sugar and caffeine.
- Doing the exercise regularly.
- Sleep enough.
- If necessary, find ways to reduce your stress level.
To provide maximum protection, the flu vaccine must be received before winter. It is administered by intramuscular injection. Immunization campaigns usually take place at the beginning of November .
What you need to know about flu shots
- The effectiveness of the flu vaccine is usually 70% to 90%. However, it may be lower in some years because the composition of the vaccine varies from year to year.
- The vaccine begins to be effective 2 weeks after vaccination.
- The protection lasts about 6 months.
- It is impossible to get the flu because of the vaccine given by injection , because this vaccine contains no live virus.
- The flu vaccine does not protect against colds or bird flu. This vaccine protects only against the virus strains it contains and not against other causes of infection of the sinuses, bronchi or lungs.
- In the elderly , the influenza vaccine reduces the risk of complications related to influenza.
Every year, experts from different countries meet in Geneva under the auspices of the World Health Organization to develop the vaccine that will be used in the following months, depending on the most active strains.
In France who can get vaccinated for free? (information for the year 2016-2017):
- pregnant women, regardless of the trimester of pregnancy ;
- people, including children from the age of 6 months, who have the following pathologies:
- chronic bronchopulmonary diseases meeting the criteria of ALD 14 (asthma and COPD)
- obstructive or restrictive chronic respiratory insufficiencies regardless of the cause, including neuromuscular diseases at risk of respiratory decompensation, upper or lower airway malformations, lung malformations or chest malformations;
- chronic respiratory diseases that do not meet the criteria for ALD but may be aggravated or decompensated by an influenza condition, including asthma, chronic bronchitis, bronchiectasis, bronchial hyperresponsiveness;
- broncho-pulmonary dysplasias treated during the previous six months by mechanical ventilation and / or prolonged oxygen therapy and / or continuous medication (corticosteroids, bronchodilators, diuretics);
- cystic fibrosis ;
- congenital heart defects cyanogenic or with PAH and / or heart failure;
- severe heart failure;
- severe valvulopathies;
- serious heart rhythm disorders that warrant long-term treatment;
- coronary diseases;
- history of stroke;
- severe forms of neurological and muscular diseases (including myopathy, poliomyelitis, myasthenia, Charcot’s disease);
- paraplegia and quadriplegia with diaphragmatic involvement;
- severe chronic nephropathy;
- nephrotic syndromes;
- sickle cell anemia, homozygotes and double heterozygotes S / C, thalassodepanocytosis;
- type 1 and type 2 diabetes;
- primitive or acquired immune deficiency (oncological and hematologic diseases, hematopoietic organ and stem cell transplants, hereditary immune deficiency, inflammatory and / or autoimmune diseases receiving immunosuppressive therapy), except persons receiving regular immunoglobulin treatment; people infected with HIV regardless of age and immunovirological status;
- chronic liver diseases with or without cirrhosis.
- obese persons with a BMI equal to or greater than 40 kg / m2, without associated pathology or with a pathology other than those mentioned above ;
- persons staying in a care facility as well as in a nursing home, regardless of their age;
- the family circle of infants less than 6 months of age, with defined risk factors for severe influenza: premature, especially those with sequelae such as broncho dysplasia and children with congenital heart disease, congenital immunodeficiency, pulmonary pathology , neurological or neuromuscular or a long-lasting condition.
In Canada, who has the right to free vaccination?
Canadian Medical Authorities Offer Free Vaccination to Those at Higher Risk of Influenza or Serious Complications:
- Young children aged 6 months to 23 months ;
- People with certain chronic diseases ;
- People 60 years and over ;
- Health workers .
In Quebec, on prescription: needle-free vaccine
Canadians aged 2 to 59 years could receive a flu vaccine administered by nasal spray .
But the CDC’s Advisory Committee on Immunization Practices (ACIP) voted and decided that with live influenza vaccine being attenuated, the nasal influenza vaccine should not be used during the 2016-2017 influenza season.
In fact, FluMist was approved by Health Canada in June 2010 and had the advantage of not requiring an injection. In addition, it offered protection against a larger number of influenza viruses because the immune system reacts more strongly to this vaccine.
However, the nasal flu vaccine has more contraindications than the vaccine given by injection. That is why, in Quebec, it is obtained only by prescription . Its composition is different: it contains live viruses of the flu. These viruses have been previously modified in the laboratory to be less virulent (they are “attenuated” viruses). This still means that there is a (minimal) risk of having the flu after receiving it. This vaccine is not suitable for the elderly or those with a weakened immune system (for example, because of cancer or AIDS treatment). In addition, it is contraindicated for children with asthma, because the administration of the vaccine through the nose can exacerbate the symptoms.
Medical treatment of influenza
Some medications are designed to relieve symptoms . For example, antipyretics lower fever. Others, such as antivirals, reduce the duration and severity of the infection, provided they are taken very early. Some people who become very ill may need to be hospitalized and require more intensive treatments .
What medicines to treat the flu?
Drugs against fever (antipyretics).
Raising body temperature is part of the normal process of fighting an infection. According to the Canadian Pediatric Society, the main reason for treating fever with paracetamol or acetaminophen(Doliprane, Dafalgan, Tylenol, Tempra, Panadol) is to relieve the pain and discomfort associated with it. However, if the temperature exceeds 39.5ºC (103.1ºF), it is important to contact your doctor.
In the case of children, give only paracetamol (acetaminophen). Acetylsalicylic acid (Aspirine) should be reserved for adults. Indeed, aspirin can cause Reye’s syndrome in children who have the flu or chickenpox. It is a very serious nervous system disease (sometimes fatal). The ibuprofen may also be used, but is at risk of stomach ulcer. This nonsteroidal anti-inflammatory drug (NSAID) also has contraindications.
Drugs that kill viruses can be given as soon as symptoms appear and at the latest within 48 hours. They must be prescribed to the following persons:
- People with severe flu right away or a quick worsening flu.
- People with influenza requiring hospitalization.
- People at risk (those who have been or should have been vaccinated and for whom the vaccine is supported because of their frailty).
- People who have been in close contact with a person with flu and who are at risk of complications.
- To reduce the severity of symptoms and the duration (about 1 day) of influenza in people with fragile health, provided they are administered at the onset of symptoms and at the latest within 48 hours of this onset .
Oseltamivir (Tamiflu) reduces the severity of influenza A and B symptoms. The effectiveness of antivirals can vary greatly as some strains of the virus are resistant to varying degrees.
Natural remedies to accompany drugs
- Consume plenty of water or other liquids (fruit juice, hot broth, etc.). Dehydration can be controlled and mucous secretions are less thick and therefore easier to expel.
- In the same vein, a humidifier will also help to make mucus secretions more fluid.
- Keep the bed. Take a lot of rest to help the immune system fight the infection.
- Unclog the nose with saline and gargle with salt water to relieve sore throat if necessary.