Flu: What Are The Symptoms Of This Viral Infection?

The flu or influenza is a disease caused by a virus that attacks the respiratory system. This is very contagious.

What are the symptoms? How to guard against it? How to treat it? Here are our explanations.

What is Flu

INFORMATION: the symptoms of the flu are very similar to the signs of the coronavirus or Covid-19. To find out more, we invite you to consult our Coronavirus section.

The flu, or influenza, is a disease caused by influenza viruses of the Orthomyxoviridae family, RNA viruses. A contagious disease, the flu first affects the respiratory system and can become complicated or present in severe forms.

How long does the flu last?

The flu usually lasts 3 to 7 days and can prevent a person from carrying out daily activities.

The different flu viruses

There are 3 types of influenza virus, with different subtypes classified according to their surface glycoproteins, neuraminidase (N), and hemagglutinin (H).

Type A flu

Type A flu is the most dangerous type. 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 transforms 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 strain of influenza in circulation.

Type A virus causes a pandemic about 3 or 4 times per 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.

Avian flu is also a type A virus that affects birds, whether they are:

  • slaughter: chickens, turkeys, quail;
  • wild: geese, ducks;
  • servants.

The virus is easily transmitted from birds to humans, but rarely between humans.

The H5N1 strain has caused several deaths in Asia, usually in people who had close contact with sick or dead poultry or who frequented live poultry markets.

Type B flu

Most often, manifestations of Type B influenza are less severe. It causes only localized epidemics. This type of flu is less prone to mutations than type A.

Type C flu

Symptoms caused by Type C flu are similar to those of a common cold. This type of flu is also less prone to mutations than type A.

Do viruses evolve?

This type of virus is constantly undergoing genetic changes or genotypic changes. This is why having the flu one year does not provide immunity against the viruses that will circulate in the following years.

So you can get new flu every year. Vaccines must be adapted each year to protect the population against new variants of the virus.

Flu and contagion: how long does it last?

An infected person can be contagious the day before their first symptoms and can transmit 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 flu virus, the signs can start to appear from the 1st day after the infection until 3 days after.

The flu, how is it caught?

The flu spreads easily, by contagion and in particular by contaminated micro-droplets that are released into the air when you cough or sneeze. The virus can also be transmitted through saliva.

Since the virus can quickly be found on the face and hands of a person with the flu, kissing and shaking hands with sick people should be avoided.

Transmission occurs more rarely through objects touched by saliva or contaminated droplets. The virus persists on the hands for 5 to 30 minutes and in the stool for several days.

On inert surfaces, the virus remains active for several hours, so avoid touching the patient’s objects such as:

  • toys;
  • Table ;
  • cutlery;
  • the toothbrush.

Flu or cold, what’s the difference?

In case of a cold:

  • fever and headaches are rare;
  • pain, fatigue, and weakness are minor;
  • the nose runs quite profusely;
  • there is no or very rare muscle pain.

Is the flu easier to catch when it’s cold?

The Italians of the 14th century believed that episodes of influenza contagion were brought on by the cold. They had therefore named it influenza di Fredo. 

They were not entirely wrong, because, in the temperate zones of the northern and southern hemispheres, the flu does indeed appear more often in winter.

But at the time, they were most likely unaware that, in the tropics, flu outbreaks can occur at any time of the year. There is no flu season!

It has long been believed that “catching a cold” reduces the body’s resistance to the flu and colds. However, nothing indicates that the cold weakens the immune system or facilitates the entry of the virus into the respiratory tract.

If the flu is more frequent in winter, it seems more likely that it is attributable to confinement inside homes, 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 out. Indeed, the mucous membranes prevent the entry of microbes more effectively when they are moist.

In addition, the dry air of winter would facilitate the survival of the virus outside the body.

When do you catch the flu?

The seasonal incidence of influenza varies according to the latitude of the country where one is and the annual virus in circulation.

In North America as in Europe, the flu season extends from November to April.

What are the potential complications?

The flu can get complicated in a number of ways.

Bacterial superinfection

Complications can occur if the flu is added:

  • a bacterial infection;
  • otitis media;
  • sinusitis;
  • post-influenza bacterial pneumonia occurs from the 4th to the 14th day after the start of the infection, most often in the elderly.

Pneumonia consistent with primary malignant influenza

Rare and serious, pneumonia leads to hospitalization in medical intensive care.

Complications involving organs other than the lungs

Complications that can affect other organs, except the lungs are:

  • myocarditis or inflammation of the heart muscle;
  • pericarditis or inflammation of the pericardium, the membrane located around the heart;
  • encephalitis or inflammation of the brain;
  • rhabdomyolysis or severe muscle damage;
  • Reye’s syndrome in the case of aspirin intake in children, causing hepatitis and acute encephalitis, is very serious.


Individuals with more fragile health are more at risk of complications and death, such as:

  • old people ;
  • immunocompromised people;
  • people with lung disease.

During pregnancy, complications include:

  • miscarriages;
  • prematurity;
  • neurological congenital malformations.

In the elderly, pre-existing cardiac, respiratory, or renal insufficiency may worsen considerably. We are talking about decompensation.

Flu: when to consult a doctor?

In the presence of the following symptoms, it is best to consult a doctor in order to detect and possibly treat the complications that may arise:

  • a fever of more than 38.5°C for more than 72 hours;
  • shortness of breath at rest;
  • chest pain.

Who is affected by the flu?

In mainland France, each year, during an influenza epidemic, between 788,000 and 4.6 million people consult their general practitioner, ie nearly 2.5 million people are affected on average by influenza each year.

Nearly 50% of them are under 18 years old. The flu has caused an average of 9,000 deaths each year since 2011, in France, with 76% of these deaths involving people over 75 years of age.

The flu affects 10 to 25% of the Canadian population each year. The vast majority of infected people recover without problems. Still, the flu is implicated in 3,000 to 5,000 deaths in Canada, usually in people who are already weakened.

The flu, or influenza, is a disease caused by influenza viruses. What are the symptoms of the flu? We offer you a list to identify them.

What are the symptoms of the flu?

Flu symptoms can last from 24 hours to 1 week or more but usually last 3 to 7 days. Most often, the temperature decreases in 2 to 4 days. Fatigue and coughing can persist for up to 2 weeks, sometimes longer.

Flu symptoms in adults

The invasion phase is manifested by the appearance of:

  • chills;
  • malaise ;
  • sudden fever above 39°;
  • muscle aches ;
  • headache.

Then, the phase of a flu-like state can manifest itself by the following signs which are present in a variable way according to the affected person:

  • high fever, which can reach 40°, although, in children under 5 and over 65, the fever may not be very high;
  • rapid heartbeat or tachycardia;
  • chills;
  • fatigue ;
  • depression which may lead to drowsiness;
  • lack of appetite or anorexia;
  • runny nose or rhinorrhea;
  • sore throat ;
  • difficulty swallowing or dysphagia;
  • veiled voice;
  • difficulty speaking;
  • burns in the chest;
  • dry cough ;
  • severe headaches in the forehead, and eyes;
  • difficulty tolerating light or photophobia.

The flu can for some people appear in the extra respiratory form, with signs affecting other organs, which may suggest that it is another disease.

These signs are:

  • digestive disorders such as viral gastroenteritis or stomach flu;
  • signs of meningitis or inflammation of the meninges, the coverings of the brain;
  • signs of encephalitis or inflammation of the encephalon, the brain;
  • signs of pericarditis or inflammation of the covering of the heart, the pericardium;
  • myocarditis or inflammation of the heart muscle;
  • myositis or inflammation of the muscles.

Other possible manifestations include:

  • a burning sensation in the eyes;
  • night sweats;
  • marked drowsiness;
  • loss of appetite;
  • joint pain.

What is called influenza-like illness, which includes basic flu symptoms, can be caused by other viruses, such as parainfluenza or respiratory syncytial virus, or be a sign of another illness.

How to recognize the flu in children?

In children, the flu can present itself differently.

Sometimes, before a year, there are almost no symptoms, or on the contrary, a very serious flu can occur.

Before 3 years and up to 5 years, there are:

  • drowsiness in about one out of two cases;
  • disturbances of consciousness;
  • digestive disorders;
  • a simple fever with no other associated signs.

Younger children are at risk, especially children under 6 months.

Some people are at higher risk of getting the flu. Furthermore, knowing the risk factors favoring the onset of the disease is essential.

Who are the people at risk?

Anyone can get the flu.

Some people, whose immunity is weaker, are however more at risk:

  • very young children, especially those who go to kindergarten, daycare, or crèche, as well as the people who are in contact with them;
  • the elderly, especially if they live in a retirement home, nursing home, or reception center. It is in this group that we find 80 to 90% of the deaths are caused by the flu;
  • health professionals, due to frequent contact with at-risk groups;
  • pregnant women ;
  • people suffering from obesity;

Also at risk are people with:

  • a chronic illness, such as AIDS;
  • kidney disease;
  • liver disease;
  • a cardiovascular disorder;
  • a lung disorder;
  • severe anemia;
  • a serious chronic neurological disease;
  • of diabetes.

What are the risk factors for the flu?

The risk factors for influenza are:

  • having a weakened immune system, due to chronic stress, lack of sleep, poor diet, etc. ;
  • frequent public places during epidemic periods such as markets, public transport, public toilets, etc. ;
  • sharing a small space with several people, for example when traveling by train, plane, or on cruise ships;
  • visiting a sick person with the flu;
  • to smoke.

Some preventive measures can be put in place to prevent the onset of the flu.

How to avoid flu contagion and protect yourself against it?

The flu usually does not have serious health consequences. However, when it occurs in people with fragile health, the infection can lead to significant, potentially fatal complications. It is therefore essential to know how to guard against it.

To protect yourself from the flu and its contagion, you should:

  • wash your hands often;
  • avoid touching their eyes, mouth, or nose, which are entry points for the virus.
  • do not get too close to an infected person in order to avoid contagion. The virus travels through micro-droplets projected into the air by sneezing and coughing. We must therefore protect ourselves accordingly.
  • if you have the flu, cough into your elbow;
  • going to public places less;
  • get vaccinated if possible before the epidemic period or at the very beginning if you have not done so and if you are a person at risk or if you are exposed to risk factors;
  • remember that people with the flu remain contagious as long as their symptoms persist.

For people who live in an institution such as a care facility, a retirement home, or a hospital, the patient must wear a surgical mask if they can bear it. As a family, this can also be done!

Boost your immunity against the flu

During flu season, almost everyone is exposed to the virus, but only some people get the flu. It depends on each person’s immune response. The immune system can be strengthened through certain measures:

  • have a healthy diet;
  • reduce consumption of alcohol, sugar, and caffeine;
  • exercise regularly;
  • get enough sleep;
  • if necessary, find ways to reduce their stress level.

Flu vaccines

To provide maximum protection, the flu vaccine should be received before winter. It is administered by intramuscular injection. Vaccination campaigns usually take place from the end of October – the beginning of November.

What you need to know about flu shots

  • the effectiveness rate of the flu vaccine is usually 70-90%. However, it may be less in some years because the composition of the vaccine changes from year to year;
  • the vaccine begins to be effective 2 weeks after vaccination;
  • protection lasts approximately 6 months;
  • it is impossible to get the flu from the vaccine given by injection because this vaccine does not contain any live virus;
  • the flu vaccine does not protect against the common cold or bird flu. This vaccine only protects against the strains of virus 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 flu-related complications.

Every year, experts from different countries meet in Geneva under the aegis of the World Health Organization to develop the vaccine that will be used in the following months, depending on the most active strains.

What are the treatments for the flu? Here are our answers.

Flu: what treatments?

Some medications are designed to relieve flu symptoms, such as:

  • antipyretics that lower fever;
  • antivirals which 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 treatment.

Medicines for fever or antipyretics

Raising body temperature is part of the normal process of fighting infection. According to the Canadian Pediatric Society, the main reason for treating fever with paracetamol or acetaminophen such as Doliprane®, Dafalgan®, Tylenol®, Tempra® or Panadol®, is to relieve the discomfort and pain associated with it. are associated.

However, if the temperature exceeds 39.5 ºC or 103.1 ºF, it is important to contact your doctor.

In the case of children, only paracetamol should be given. Acetylsalicylic acid or Aspirin® 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 disease of the nervous system that is sometimes fatal.

Ibuprofen can also be used but poses a risk of stomach ulcers. This nonsteroidal anti-inflammatory drug or NSAID also has contraindications.

Antiviral drugs

Drugs that destroy the viruses, or antivirals, can be administered as soon as symptoms appear and at the latest within 48 hours of their appearance. They should be prescribed to the following people:

  • people with severe flu from the outset or rapidly worsening flu;
  • people with influenza requiring hospitalization;
  • people at risk, in particular, those who have been or should have been vaccinated and for whom the vaccine is reimbursed because of their fragility;
  • people who have been in close contact with someone with the flu and who are at risk of complications;
  • to reduce the severity of symptoms and the duration of approximately 1 day of influenza in people with fragile health, provided that they are administered as soon as symptoms appear and at the latest within 48 hours of this appearance.

Oseltamivir or Tamiflu® reduces the severity of symptoms of influenza types A and B. The effectiveness of antivirals can vary greatly, as certain strains of the virus are resistant to them to varying degrees.

Natural remedies to accompany medication

To cure flu in a natural way, it is recommended to:

  • consume plenty of water or other liquids such as fruit juices or hot broths. We can thus combat dehydration and ensure that mucus secretions are less thick and therefore easier to expel;
  • along the same lines, a humidifier will also help loosen mucus secretions;
  • keep the bed. Get plenty of rest to help the immune system fight infection;
  • clear the nose with saline solution;
  • gargle with salt water to relieve sore throats if necessary.

In the case of the flu, there are some complementary approaches that can help treat it in a more natural way. Discover them.

Influenza: complementary approaches

Prevent the flu with natural methods

Ginseng ou Panax ginseng

By strengthening the immune system, taking ginseng could help prevent the flu, in conjunction with a flu shot.

In influenza-vaccinated subjects, standardized extracts of Asian ginseng, such as G115® 100 mg twice daily 12 and American ginseng 19 or COLD-fX® 200 mg twice daily, markedly reduced the risk of contracting a respiratory infection compared to a placebo.

Dosage: Take 100-200 mg, 2 times daily, of a standardized ginseng extract containing 4-7% ginsenosides.

Echinacea or Echinacea sp

A large number of people use echinacea for the purpose of preventing colds and flu. However, most clinical trials conducted with echinacea have focused on the prevention of colds only with rather positive results.

It would be logical to think that echinacea also helps prevent the flu because of its immunomodulatory action. However, the current scientific data are insufficient to be able to confirm this.

Astragale or Astragalus membranaceus or Huang Qi

The dried root of this plant is used in traditional Chinese medicine to increase the body’s resistance to viral infections.

The studies conducted to test its effectiveness, carried out in China, involved a small number of subjects and had a questionable methodology. Astragalus root should only be taken for prevention.

Ginger or Zingiber officinale

According to traditional Chinese medicine, ginger helps prevent infections of the respiratory system when taken at the onset of the first symptoms of a cold or flu.

Cure the flu with natural methods

Andrographis ou Andrographis paniculata

The aerial parts of this plant have been used for hundreds of years to treat fever and respiratory infections in several traditional Asian medicines.

The authors of a review of 4 randomized, double-blind trials concluded that Andrographis, alone or in combination with Eleutherococcus, is more effective than a placebo in treating uncomplicated respiratory infections such as a cold, flu, or pharyngitis. The authors of another synthesis came to the same conclusion.

Some research has been done on young patients, with positive results.

The mechanism of action of the plant has not yet been elucidated, but in vitro tests indicate that it would have effects:

  • immunostimulants;
  • anti-inflammatories;
  • febrifuges, that is to say reducing or eliminating the fever.

Dosage: Take 400 mg of standardized extract containing 4 to 6% andrographolide, 3 times a day.

Echinacea or Echinacea sp

There is insufficient scientific data to conclude the effectiveness of echinacea in reducing flu symptoms.


A systematic review aimed to assess the effectiveness of Oscillococcinum, a popular homeopathic treatment for the prevention and treatment of influenza. Seven randomized clinical trials were included. 

The authors conclude that Oscillococcinum has no preventive effect and a very modest therapeutic effect, namely the reduction of the infection time by 0.26 days.

Black elderberry – berries or Sambucus nigra

A double-blind, placebo-controlled trial involving 27 subjects showed that a black elderberry extract, such as Sambucol® syrup, was significantly superior to placebo in rapidly relieving flu symptoms.

Another double-blind, placebo-controlled trial in 60 subjects with influenza types A and B showed that elderberry syrup had the effect of reversing flu symptoms 4 days earlier and reducing significantly increased the use of rescue medication compared to subjects taking the placebo.

White willow or Salix alba

Commission E and ESCOP recognize the virtues of white willow to treat diseases that are accompanied by:

  • fever ;
  • rheumatism;
  • headache.

The British Herbal Compendium recommends it for treating colds and flu.

Black elderberry – flowers or Sambucus nigra

The British Herbal Compendium recommends the use of black elderflower to treat feverish conditions. The World Health Organization or WHO recognizes the traditional use of elderflowers as:

  • diaphoretic, that is to say, which causes sweating;
  • expectorant.

Acupuncture and acupressure

Acupuncture may help you feel better and speed up recovery from the flu. A study carried out in China, uncontrolled and non-random, shows that acupuncture reduces fever.

Furthermore, another study carried out in the Czech Republic, also uncontrolled and non-random, seems to indicate that acupressure, used in particular in shiatsu, is effective in treating flu symptoms. More specifically, this study focuses on the “Chromassi” method, which consists of combining massage and acupressure.

This method is based on the theory of biological rhythms and traditional Chinese medicine. Like acupuncture, acupressure acts on the meridians to restore energy balance.

Chinese pharmacopoeia

There are at least 3 over-the-counter preparations that are used in Chinese medicine for the flu:

  • Xiao Chai Hu Wan: this preparation would be very effective in fighting against respiratory infections that are slow to heal when the body no longer has the energy to do so;
  • Yin Qiao San: created to fight infectious diseases in children, Yin Qiao San helps fight spring and summer flu;
  • Yu Ping Feng San or Wan: this preparation works by reducing the frequency and intensity of respiratory infections such as allergic rhinitis, colds, or flu.

Beware of so-called natural or homeopathic flu vaccines. These are not vaccines, but at best treatments, that can boost immunity. People at risk should be vaccinated with a real vaccine to avoid serious complications.

Image Credit: Photo by Pixabay pexels.com

Leave a Reply

Your email address will not be published. Required fields are marked *