Flu can occur at any age and can cause illness ranging from mild to severe. Young children, pregnant women, and the elderly are groups that should not underestimate this respiratory infection.
What You Need to Know About the Flu
Definition of the Flu
The flu is an acute viral infection. The illness develops when the influenza virus infects and attacks the respiratory system, including the nasal passages, throat, bronchi, and may involve the lungs.
Generally, the flu is mild, and individuals can recover on their own within about 2-7 days. However, in certain special cases such as immunocompromised individuals and those with chronic illnesses, the flu can become dangerous and lead to severe complications that may result in death.
The flu can affect everyone, with infection rates of 5-10% in adults and 20-30% in children. The danger of the flu lies in its high infectivity, leading to a risk of outbreaks. In tropical regions like Vietnam, the flu often occurs during the rainy season but can spread at any time of the year.
The flu is an acute viral infection.
There are three different types of influenza viruses that affect humans, including:
- Type A Influenza: Also known as seasonal flu, it is found in many animal species. The influenza A virus frequently mutates, creating many new strains; it is known to cause highly infectious flu pandemics. Current circulating subtypes include A (H1N1) and A (H3N2).
- Type B Influenza: Similar to type A, the influenza B virus can also cause seasonal outbreaks. However, unlike type A, the B virus generally changes more slowly in terms of genetic and antigenic properties and only infects humans; it does not cause large epidemics.
- Type C Influenza: The influenza C virus is also found in humans but causes milder respiratory symptoms compared to types A and B and is less likely to cause serious complications.
Flu Symptoms
The flu can cause symptoms that range from mild to severe. Many people often confuse the flu with a cold due to initial symptoms such as a runny nose, sneezing, and a sore throat. However, colds usually develop slowly, while flu symptoms appear rapidly and suddenly. You may start noticing signs of illness within 1-7 days, typically 48-72 hours after exposure to the flu virus.
The first common symptom is a high fever ranging from 39 to 41 degrees Celsius. Children with the flu often have higher fevers than adults. Individuals with the flu may also experience one or more of the following signs:
- Chills and sweating
- Dry cough
- Sore throat
- Nasal congestion and runny nose
- Headache
- Fatigue and shortness of breath
- Nausea and diarrhea (more common in children than adults)
Most flu symptoms will gradually disappear after about 4-7 days. A dry cough and fatigue may persist for weeks, along with the fever returning intermittently.
If flu symptoms worsen or persist without signs of improvement after one week, or if the fever lasts more than three days, you should see a doctor. More concerning symptoms include difficulty breathing, chest pain, loss of consciousness, seizures, and signs of dehydration (such as infrequent urination or no urination); in such cases, the patient needs immediate emergency care. These are warning signs that the flu may be evolving into a more serious condition, such as pneumonia.
Causes of the Flu
The flu is caused by the influenza virus. The influenza virus exists in the air and can enter the body when we touch our eyes, nose, or mouth.
Transmission Pathways of the Flu
The influenza virus can spread directly through respiratory droplets when an infected person coughs, sneezes, or talks, releasing droplets containing the virus into the air, which can remain on surfaces and objects. Contact with these droplets increases the risk of contracting the flu.
In crowded places, direct contact is an ideal condition for the flu to spread rapidly. An infected person can transmit the virus to others from 1 day before symptoms appear up to 5-7 days after becoming ill. In young children or those with weakened health, the infectious period may extend up to about two weeks.
High-Risk Groups for the Flu
Anyone can contract the flu. However, high-risk groups include:
Anyone can get the flu.
- Children and the Elderly: Seasonal flu tends to occur more frequently in children aged 6 months to 5 years and in elderly individuals aged 65 and over. The CDC warns that approximately 20,000 children under 5 are hospitalized each year due to flu-related complications.
- Obese Individuals: Those with a Body Mass Index (BMI) of 40 or higher are at a higher risk of contracting the flu compared to those with a healthy weight.
- Immunocompromised Individuals: People undergoing cancer treatment, taking immunosuppressive drugs, using steroids for extended periods, or experiencing conditions such as organ transplants, blood cancers, or HIV/AIDS are at increased risk of the flu and complications.
- Individuals with Chronic Illnesses: The flu also commonly occurs in individuals with chronic conditions, including lung diseases (such as asthma), diabetes, cardiovascular diseases, neurological disorders, digestive issues, kidney or liver abnormalities, and blood disorders.
- Pregnant Women and Postpartum Women: Pregnant women—especially in the second and third trimesters—and women within two weeks after delivery are also at significant risk of complications from the flu.
Complications of the Flu
In young individuals and those with good health backgrounds, the flu typically does not have severe effects and can resolve within a maximum of two weeks without long-lasting impacts.
However, in young children under 5, the elderly, and those with poor health, the flu can lead to complications such as pneumonia, bacterial superinfection, encephalitis, meningitis, ear infections, sinus infections, myositis, or rhabdomyolysis, multi-organ damage such as kidney failure, respiratory failure, and exacerbation of chronic conditions like congestive heart failure, asthma, or diabetes. Among these, pneumonia is one of the most serious issues. In older adults and those with chronic diseases, flu-related pneumonia can be life-threatening.
Pneumonia is a dangerous complication of the flu, especially for the elderly and those in poor health.
How to Diagnose the Flu
The initial step in diagnosing the flu involves the physician examining and assessing flu symptoms if present.
Additionally, there are several tests to detect the influenza virus in respiratory specimens, including:
- RT-PCR: This method is highly specific and is the most characteristic test for detecting and classifying the influenza virus. Results are available within 4-6 hours.
- Fluorescent Immunoassay: This method has lower sensitivity and specificity than RT-PCR but can provide results within a few hours of sample collection.
- Rapid Influenza Diagnostic Tests (RIDTs): These tests provide results within 10-15 minutes but are not as accurate as other flu tests; thus, it is still possible to have the flu even if the rapid test result is negative. The effectiveness of these tests depends significantly on the patient’s age, duration of illness, type and quality of the specimen, and strain of the influenza virus. Rapid tests have low sensitivity and specificity, so they should be combined with other diagnostic methods when the rapid test result is negative.
- Virus Isolation: This is not a screening test, but during flu outbreaks, it should be performed on specimens collected from individuals suspected of having the flu, especially those with epidemiological factors related to the flu.
- Serological Testing: This test provides quick results but lacks high sensitivity and specificity.
Depending on the type of diagnostic test, timing of specimen collection, type and quality of the specimen, and the active virus strain, you may still be considered a flu case despite a negative test result—this situation is referred to as a false negative. Therefore, a final conclusion should also consider symptoms and clinical assessments from the physician.
Currently, flu patients may also need to be tested for COVID-19 to rule out the possibility of contracting both flu and COVID-19 simultaneously.
How to Treat the Flu
Currently, there is no definitive treatment for the flu; there are only methods to alleviate the symptoms, helping patients feel more comfortable and at ease.
Rest
Typically, the flu can resolve on its own after a short period if the patient takes time to rest and drinks plenty of fluids to help the body gradually combat the infection. Smoking or drinking alcohol during this time should be avoided; it is also advisable to limit tea, coffee, and other stimulating beverages to prevent further fatigue.
In terms of nutrition, flu patients should enhance their diet by adding dark green, red, and yellow fruits and vegetables to boost their immune system and support a quick recovery.
Use Pain Relievers
Taking over-the-counter pain relievers should be considered carefully. Children and teenagers recovering from flu-like symptoms should not use aspirin to prevent the risk of Reye’s syndrome, a condition characterized by acute brain damage and fatty liver degeneration following acute viral infections.
Flu patients can use cold medications, nasal drops, or sprays that are available over-the-counter to relieve uncomfortable flu symptoms such as coughing, runny nose, and headaches.
Use Antiviral Medications
For those with severe infections or at high risk for complications, antiviral medications are essential for treating the flu. Timely and proper use of these drugs can reduce symptom severity and shorten the duration of illness. This is also a way to prevent the progression of flu complications, especially in older adults or those with weakened immune systems.
Currently, three antiviral medications are recommended for flu treatment: oseltamivir (Tamiflu®), zanamivir (Relenza®), and peramivir (Rapivab®). These medications work by interrupting the function of the neuraminidase enzyme on the virus’s surface and preventing the release of viral particles from infected host cells.
These antiviral drugs can be used for cases of Influenza A and B and are most effective within 48 hours of the onset of flu symptoms. Therefore, early diagnosis and treatment are crucial.
Antiviral medications may cause side effects such as nausea and vomiting in some individuals. Patients are advised to take these medications with food to mitigate these side effects.
Antibiotics
Antibiotics are ineffective in treating the flu because they cannot kill the virus that causes the illness.
However, the flu can weaken the immune system, making patients more susceptible to other bacterial infections. If you notice flu symptoms returning after they have subsided, it is advisable to seek medical attention as soon as possible. At this point, antibiotics may be necessary to prevent the risk of infection.
How to Prevent the Flu
Get a Flu Shot Every Year
The best way to prevent the flu is to get vaccinated annually. Because the flu virus continuously mutates, a new vaccine is produced each year based on research from scientists regarding the virus’s pathogenic capabilities. Just one booster shot each year can effectively protect you against the flu. According to the Department of Preventive Health – Ministry of Health, the vaccine has a very high protection rate of up to 90%. In older adults, flu vaccination can reduce the incidence of illness by up to 60% and the mortality rate from flu-related issues by 70-80%.
Some flu vaccines currently available in Vietnam include Vaxigrip 0.25ml, Vaxigrip 0.5ml, and Influvac 0.5ml. The Centers for Disease Control and Prevention (CDC) recommends that everyone aged 6 months and older should receive a flu vaccination. This includes children, individuals with chronic heart/lung diseases/asthma/immunocompromised conditions, those aged 65 and older, pregnant women, and individuals frequently in contact with patients, as they are at higher risk of illness.
Annual vaccination is the most effective way to prevent the flu.
Establish Healthy Lifestyle Habits
Building and maintaining the following lifestyle habits can significantly reduce your risk of contracting the flu and other infectious diseases.
- Wash Hands Frequently: Keep hands clean and avoid direct contact with eyes, nose, and mouth. Regularly wash hands with warm water and soap for 30 seconds or use hand sanitizer.
- Avoid Close Contact in Crowded Places When Experiencing Flu Symptoms: Avoid socializing, working, or studying in close proximity to others if you suspect they are infected with the flu without protective measures like wearing a mask. If you notice flu symptoms, self-isolation is crucial to ensure the health of those around you. It is best to stay in a separate room or at home for at least 24 hours after fever has subsided.
- Clean Surfaces: Regularly clean and disinfect high-touch surfaces in your home, office, and public spaces, such as doorknobs, phones, toys, and tables, to reduce the risk of flu transmission.
- Exercise Regularly: Individuals who have a habit of daily physical activity often experience less severe symptoms and recover faster if they contract the flu.
