Flu: causes, symptoms, effective treatment and prevention

Flu is one of the most common viral infections affecting millions of people every year, especially in the cold season. Although it may seem like a simple cold, flu can lead to serious complications, especially in vulnerable people (children, elderly, chronically ill).

In this article you will find out about the causes, symptoms, treatment and how to prevent getting sick and get through the flu season.

What is flu? The viruses that cause infection

Influenza is a highly contagious viral infection caused by influenza viruses (type A, B or C). Of the 3, only influenza A and B viruses can cause clinically significant pathology, causing seasonal epidemics annually, while influenza C virus causes a mild form of the disease (***, 2024).

Causes of influenza outbreaks. Risk factors

Due to sudden temperature changes and the emergence of influenza viruses in the cold season, the immune system is more vulnerable, which leads to easier infection of the body.

How is flu spread? The incubation and contagious periods

The flu virus enters through the nose, mouth or eyes and may enter the lungs where it multiplies. It is easily transmitted by aerosols (coughing or sneezing) but also by direct contact with contaminated surfaces. It has been shown to live 1-2 days on surfaces, 5 minutes on skin and 15 minutes on paper (Bean, et al., 1982). Children are more likely to become infected and further transmit the virus. Statistically one sick person will infect 1-3 healthy people. (***, 2024)

The infected person is contagious 1-2 days before the first symptoms appear and 5-7 days after the onset of illness. The risk of infecting others usually disappears around the seventh day of illness. (***, 2024)

People most at risk of infection with influenza viruses

• Children under 2 years of age;
• Adults over 65 years of age;
• Pregnant women;
• People who have cardiovascular, respiratory, hematologic, liver, endocrine, kidney, neurologic, metabolic, oncologic, respiratory, hematologic, endocrine, kidney, neurologic, metabolic, oncologic diseases or a weakened immune system;
• Those with a body mass index (BMI) of 40 kg^/m2 or higher;
• Those around infected persons;
• Those who do not follow good hygiene to prevent illness;
• Persons not immunized with the influenza vaccine. (***, 2024)

Flu symptoms. How to recognize the disease in time?

Flu symptoms appear suddenly and violently, usually 2 days after infection and may be the following (***, 2024):

• High fever of 39-40°C;
• Chills;
• Headache;
• Myalgia (muscle pain);
• Dysphagia (sore throat);
• Stuffy or runny nose;
• Dry cough that may become expectorant;
• Severe fatigue;
• Lack of appetite.

In newborns and infants, non-specific symptoms such as vomiting and diarrhea, abdominal pain may occur, which may be more likely to indicate a bacterial infection (***, 2024).

Symptoms last on average 3-4 days, the cough may persist for 1-2 weeks.

Signs and symptoms that more easily distinguish influenza from the common cold are as follows (***, 2024):

Signs and symptoms	Flu	Common cold
Onset of symptoms	Abrupt	Gradual
Fever	39-40°C	Rare
Pain	Pronounced	Mild
Chills	Frequent	Rare
Fatigue, muscle weakness	Moderate-severe	Mild-moderate
Sneezing	Sometimes	Common
Chest discomfort, cough	Common	Mild to moderate
Stuffy nose	Sometimes	Common
Sore throat	Sometimes	Common
Headache	Common	Rare

When to go to the doctor? Signs requiring medical attention

At the onset of symptoms it is advisable to contact your family doctor or pediatrician and follow their advice before the actual consultation. Children under 5 years of age, especially children under 2 years of age and chronically ill children, must be seen by a doctor.

In the following cases an emergency assessment by a physician is necessary (***, 2024):

• Presents respiratory disturbances (difficulty in breathing, rapid and wheezing breathing);
• Chest pain or pressure;
• Dizziness;
• Confusion, patient not interacting or alert;
• Has an altered general condition;
• Temperature is still elevated after taking antipyretics or has convulsions.

In children we are talking about the same complications, plus (***, 2024):

• Cyanosis (bruising) of the lips or face;
• Vomiting;
• Refusal of fluids, showing signs of dehydration (dry mucous membranes, absence of tears, sunken eyes, decreased urination, excessive thirst, fatigue, muscle weakness, headache, dizziness);
• Some symptoms, such as fever or cough, improve but return later or worsen.

What investigations are needed to diagnose influenza?

The doctor will take a history, asking about symptoms and history of illness, then physically examine the patient. Influenza is usually easily distinguished from other flu by specific symptoms.

However, some paraclinical (laboratory) tests may also be performed, such as a qualitative screening test (necessary to detect the presence of Influenza A and B influenza viruses – by taking nasal secretions or nasopharyngeal aspirate) which is recommended to be done within 4 days of the onset of symptoms, as well as a hemoleocugram, blood count, ESR, fibrinogen, C-reactive protein. To exclude the diagnosis of pneumonia, a chest X-ray may be necessary. (***, 2022)

Complications of influenza. Risks and dangerous course of the disease

Untreated in time, influenza can evolve unfavorably, leading to (***, 2016):

• Pneumonia (acute inflammation of the lungs caused by infection);

• Acute laryngitis (sudden inflammation of the larynx);
• Acute laryngotracheobronchitis/acute tracheitis/croup (inflammation of the tracheal mucosa) – common in children under 6 years;
• Acute bronchiolitis (lung infection causing inflammation of the bronchioles) – common in babies and children;
• Exacerbation of bronchial asthma (chronic airway inflammation);
• Otitis media (middle ear infection causing inflammation and fluid accumulation);
• Sinusitis (inflammation of the nasal sinuses);
• Myocarditis (inflammation of the heart muscle)
• Encephalitis (inflammation of the brain)
• Myositis (inflammation of skeletal muscle tissue), rhabdomyolysis (disintegration of muscle tissue)
• Dehydration.

Flu treatment. Medicines and herbal remedies

Do not administer medication without first consulting a doctor. Monitor your health and contact your doctor if symptoms worsen or complications develop.

As a viral infection, antibiotics are contraindicated. They may only be necessary in the case of a bacterial superinfection diagnosed by a doctor.

The following are recommended (***, 2024), (Iftikhar, 2024):

• Home isolation with bed rest;
• Hydration (water, fresh juices, soups, you can consume star anise, clove, turmeric, green or black teas if there are no contraindications);
• Eating foods rich in vitamin C (citrus fruits, strawberries, blueberries, raspberries, pineapple, kiwi, mango, cabbage, tomatoes, green peppers, broccoli, white and sweet potatoes, etc.) and zinc (lamb, beef, pork, poultry, fish and other seafood, milk and dairy products, eggs, pumpkin seeds, cabbage, peas, beets, etc.)
• Take steam or essential oil inhalations to decongest the nose and soothe coughs;
• Nasal decongestion using saline, seawater, drops or nasal sprays with decongestants; in addition, in children, nasal secretions may need to be suctioned using a nasal pump or aspirator;
• Pain relief and temperature lowering using analgesics/antipyretics/anti-inflammatories (paracetamol and/or ibuprofen; aspirin is contraindicated in children under 16 years of age because of the risk of Reye’s syndrome, a rare and severe condition that mainly affects the brain and liver);
• Take orally dispersible tablets to moisturize the throat, cough suppressants;
• Treat vomiting and diarrhea as directed by your doctor;
• Antivirals (oseltamivir-based) should only be given on doctor’s advice, on prescription, after assessment of the patient (they are most effective if given within the first 48 hours of onset of symptoms);
• Use a humidifier to increase humidity in rooms where the air is dry.

How to prevent infection? Tips and protective measures

Vaccination is the main way to prevent influenza and its complications. Because seasonal influenza viruses mutate from season to season, annual vaccination is necessary. The peak of the flu season is usually between December and February, but cases are present both before and after, and may even be reported in April. As immunity is acquired in 2-3 weeks, it is advisable to get vaccinated as early as possible (late September – early October). In exceptional cases, it can also be done in spring. (***, 2024)

People who should be vaccinated as a priority, according to the World Health Organization (***, 2023):

• Children older than 6 months(if younger than 9 years of age and not previously vaccinated, 2 doses of vaccine should be given, 1 month apart);
• Pregnant women (this will generally protect babies up to 6 months after birth);
• The elderly over 60 years of age;
• Those with chronic diseases.

Who should not get vaccinated or should seek medical advice beforehand (***, 2023):

• Children younger than 6 months;
• People with severe allergies to the vaccine or vaccine components;
• Those with moderate to severe illness, with or without fever (should wait until they recover to vaccinate);
• People with a history of Guillain-Barré syndrome (a severe paralytic illness).

Children aged ≥ 6 months and < 19 years, pregnant women, persons aged ≥ 19 years and < 65 years in one of the following situations (chronic cardiovascular disease, chronic respiratory disease, chronic kidney disease, chronic liver disease, chronic neurologic disease,metabolic diseases, oncologic diseases, autoimmune diseases, congenital malformations, obesity, asplenia, persons with HIV/AIDS infection, immunosuppressive therapy, transplantation, congenital immunosuppression), persons over 65 years of age and medical and auxiliary staff must contact prescribing physicians for the issuance of a 100% compensated prescription. (Bihor, 2024)

Persons aged ≥ 45 years and < 65 years, without chronic diseases, shall apply to prescribing physicians for the issuance of a compensated prescription 50% (Bihor, 2024).

The rest of the population not falling into any of the above situations will be able to purchase the vaccine at full price. (Bihor, 2024)

The most vulnerable are children under 6 months who cannot be vaccinated. They can be protected by vaccinating everyone who comes into contact with them and by observing good hygiene.

As the community is the place where most illnesses occur, certain measures must be taken in terms of personal hygiene and the hygiene of the premises where activities are carried out (***, 2024):

• Hand hygiene: hands should be washed frequently (minimum 20 seconds) and/or disinfected (before eating, after using the toilet, after coughing/sneezing and whenever necessary);
• Respiratory hygiene: sneeze/cough into a disposable napkin or elbow fold, then immediately throw the napkin in the trash and wash/disinfect hands;
• Hygiene of the premises: frequented areas will be aired frequently (at least 10 minutes) and surfaces will be cleaned and disinfected before use;
• Exchange of personal items and touching eyes, nose and mouth with dirty hands should be avoided;
• Wearing the mask in enclosed and crowded spaces is also recommended;
• In case of illness, avoid re-entry into the collective.

As regards the choice of disinfectant products to prevent infection with influenza viruses, you will find a multitude of effective products in the Klintensiv portfolio.

Influenza is one of the most common respiratory infections, which can lead to complications requiring hospitalization in the presence of incompletely developed immunity such as that of children or the presence of chronic diseases. Annual vaccination and good hygiene can significantly reduce the risk of illness. Identifying symptoms correctly and acting quickly can prevent serious complications. Be informed, protect yourself and see your doctor at the first signs of illness to protect your health and avoid further transmission later in the flu season.

Note: The information in this article is for information purposes only. If you have specific symptoms, contact your GP for advice.

Photo source: Shutterstock

Sources:

***. (2016). Retrieved from https://www.cdc.gov/flu/about/disease/complications.htm

***. (2022). Retrieved from https://my.clevelandclinic.org/health/diagnostics/22716-flu-influenza-test

***. (2023). Retrieved from https://www.nhs.uk/conditions/flu/

***. (2024). Retrieved from https://www.cdc.gov/flu/highrisk/index.htm

***. (2024). Retrieved from https://www.mayoclinic.org/diseases-conditions/flu/symptoms-causes/syc-20351719

***. (2024). Retrieved from https://www.cdc.gov/flu/signs-symptoms/index.html

***. (2024). Retrieved from https://www.webmd.com/cold-and-flu/how-long-flu-contagious

***. (2024). Retrieved from https://www.mayoclinic.org/diseases-conditions/flu/symptoms-causes/syc-20351719

***. (2024). Retrieved from https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/flu-influenza

***. (2024). Retrieved from https://www.yalemedicine.org/conditions/flu

Bean, B., Moore, B. M., Sterner, B., Peterson, L. R., Gerding, D. N., & H. H. Balfour, J. (1982). Survival of Influenza Viruses on Environmental Surfaces. The Journal of Infectious Diseases, 146(1), 47-51.

Bihor, D. (2024). Retrieved from https://www.dspbihor.gov.ro/2024/09/Comunicate%20de%20presa/Comunicat_presa_25092024.pdf

Iftikhar, N. (2024). Retrieved from https://www.healthline.com/health/natural-flu-remedies#zinc