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- Symptoms of Influenza A
- Is influenza A contagious?
- Treatments for Influenza A
- How long does influenza A last?
- Is influenza A dangerous?
- High-risk groups of influenza A
- What to do if infected with influenza A?
Influenza A
Influenza A is an acute respiratory viral infection (ARI), a respiratory illness caused by infection with the influenza A virus H1N1, characterized by the sudden onset of high fever, chills, cough, runny nose, sore throat, headache, and muscle aches. Most influenza A symptoms are mild and typically go away on their own within 5-7 days. However, those with severe symptoms may experience a persistent high fever of 38°C or higher for 7-10 days or longer, as well as other serious complications such as severe pneumonia, shortness of breath, rapid breathing, respiratory failure, seizures, and death. Those experiencing flu-like symptoms and an abrupt onset of high fever should seek medical attention as soon as possible for a prompt diagnosis.
What causes influenza A?
Influenza A is caused by infection with the influenza A virus subtype H1N1, which spreads from person to person through direct contact with bodily secretions such as nasal discharge, saliva, phlegm, or respiratory droplets from coughing and sneezing, or indirect contact with virus-contaminated objects such as doorknobs, handrails, or personal items. The hand with the virus is then touching the nose and mouth, entering the upper respiratory tract in the nasal cavity, sinuses, and throat. The virus then quickly enters the viral proliferation and replication period before descending into the lower respiratory tract in the larynx, bronchi, and lungs. Individuals may or may not exhibit symptoms and can transmit the virus to others within 1-3 days.
Symptoms of Influenza A
Influenza A symptoms, duration of illness, and severity of the symptoms vary from person to person, depending on age, underlying health conditions, and immunity. Symptoms can range from asymptomatic to mild to severe, which constitute a medical emergency, as follows:
Common symptoms of Influenza A
- Sudden onset of high fever, chills
- Cough, dry cough
- Sore throat
- Sneezing, stuffy nose, runny nose
- Fatigue, weakness
- Headache
- Loss of appetite
- Nausea, vomiting
- Diarrhea, loose stools
- Body aches, muscle aches, joint pain
Severe symptoms of Influenza A
- Persistent high fever above 38 degrees Celsius for more than 1 week
- Pneumonia, severe pneumonia
- Shortness of breath, rapid breathing
- Rapid heartbeat, heart palpitations
- Hypotension
- Respiratory failure
- Febrile seizures (particularly in young children)
- Death
Is influenza A contagious?
Influenza A is highly contagious and can be transmitted from person to person quickly, particularly during the rainy season (June-October) and the winter (December-March) every year. Influenza A virus is a flu strain that mutates (changes) more quickly, spreads more rapidly, and causes more severe symptoms than Influenza B. Once influenza A enters the body, it develops in 2 phases as follows:
- Influenza A Incubation Period: The first 1-3 days after infection (rarely up to 5 days). An infected person may not have symptoms yet, but can immediately transmit the virus to others.
- Influenza A Symptomatic Period: 1–7 days after infection. Those infected with influenza A can transmit the virus to others from day 1 to day 7 after infection,n and will exhibit full symptoms on day 3 after infection.
Most people with influenza A will gradually improve and recover within 4–7 days. Those whose symptoms do not improve or worsen over time should seek medical attention at the hospital as soon as possible for a thorough physical examination due to potential disease complications that may occur, such as influenza A spreading to the respiratory tract, pneumonia, bronchitis, ear infection, or asthma exacerbation.
Diagnosis of influenza A
Doctors will diagnose influenza A by asking about symptoms, symptom onset date, duration of symptoms, and underlying medical conditions, and performing a physical examination to differentiate influenza A from the common cold and other types of respiratory viruses, as follows:
Taking medical history to differentiate between the common cold and influenza
- Onset of symptoms: Common colds usually have a gradual symptom onset, while influenza usually has a sudden onset of fever and accompanying other symptoms.
- Severity of symptoms: Common colds usually have milder symptoms than influenza.
- Duration of symptoms: Common colds can go away on their own within 7 days, while influenza may cause a persistent high fever for 7-10 days or longer.
- Other associated symptoms: In addition to the common cold, influenza can cause nausea, vomiting, and diarrhea, particularly in children.
PCR Test
Collecting samples of bodily secretions from the nasal cavity, throat, or tissue and sending them to a clinical laboratory to amplify the RNA of the virus for detection. The test can accurately identify the strain of the common cold virus or influenza A, B, or C virus. The common cold virus can be caused by one of over 200 types of cold viruses, such as Rhinovirus, whereas influenza can be caused by A, B, or C virus infections. Influenza A is further classified into 2 subtypes: influenza A H1N1 (the most pandemic strain) and influenza A H3N2.
Chest X-ray
Examine the lungs, pleura, bronchi, and diaphragm for signs of diseases or abnormalities such as pneumonia, bronchitis, or infection.
Treatments for Influenza A
If the diagnostic test results indicate influenza A, the doctor will prescribe the oral antiviral drugs Oseltamivir or Zanamivir as soon as possible. These medications contain the inhibitor of viral enzyme Neuraminidase, which inhibits the spread of the H1N1 virus, preventing the spread of infection from infected cells to healthy cells and helping to accelerate the elimination of the virus from the body. These medications are most effective if administered within 48 hours of infection. A doctor may prescribe antiviral medication for more severe cases or high-risk children, which is most effective if taken within the first few days of illness.
How long does influenza A last?
More than 90% of people with influenza A have mild symptoms and can recover on their own within 5-10 days without specific treatment. They can also relieve symptoms by taking over-the-counter paracetamol or ibuprofen, which can be purchased at general pharmacies, and getting enough rest, drinking plenty of water, and staying warm.
Is influenza A dangerous?
Influenza A is one of the influenza strains with a high degree of danger, particularly in high-risk groups such as the elderly (65 and older), young children (under the age of 5), and pregnant women, as it can lead to complications such as severe pneumonia, septicemia, and death. Those in high-risk groups should therefore receive the influenza vaccine against all 4 strains.
High-risk groups of influenza A
High-risk groups that may experience severe symptoms or complications if infected with the influenza A virus include:
- Children under the age of 5 (particularly young children under the age of 2)
- Elderly people over 65 years old
- Pregnant women or postpartum women within 2 weeks (the vaccine is safe for both pregnant and breastfeeding women)
- Obesity, those weighing over 100 kilograms, or a Body Mass Index (BMI) of more than 35 kg/m²
- Individuals with intellectual disabilities who are unable to assist themselves.
- Patients with 7 common chronic diseases: chronic obstructive pulmonary disease (COPD), heart disease, kidney failure, asthma, diabetes, stroke, and cancer patients undergoing chemotherapy.
- Individuals with pneumonia, bronchitis, thalassemia, liver disease, or immunodeficiency, and individuals infected with HIV who are symptomatic.
Quadrivalent Influenza Vaccine
The World Health Organization (WHO) recommends that the general public, and particularly high-risk groups, receive a quadrivalent influenza vaccine to boost the body’s immune system to protect against 4 types of influenza viruses. The vaccine is safe, reduces the severity of illness if infected, and is effective against all 4 strains of influenza viruses. A single shot of the vaccine can protect against:
- Influenza A (H1N1) virus
- Influenza A (H3N2) virus
- Influenza B (Victoria lineage) virus
- Influenza B (Yamagata lineage) virus
What to do if infected with influenza A?
- Take antipyretic medication such as paracetamol or ibuprofen to help reduce fever, chills, headaches, and muscle aches. *Do not take Aspirin.
- Avoid contact with others: Refrain from going to school, work, or public places to help prevent the spread of the virus.
- Wear a protective mask: Those who must come into contact with infected individuals, those with low immunity, or high-risk groups should wear a protective face mask when out in public places.
- Get enough rest: Infected individuals should get enough sleep, keep warm, and drink plenty of water to allow their bodies to fully fight against the virus.
- Wash hands frequently: Infected individuals should wash their hands frequently with soap and water regularly or use alcohol-based hand sanitizer regularly.
- Constantly monitor symptoms: If severe symptoms develop, seek medical attention at the hospital right away to prevent potential complications.
Influenza A: A Dangerous but Preventable and Treatable Virus
Influenza A H1N1 and H3N2 are the cause of global influenza epidemics and deaths in populations every year, since influenza A viruses are virulent, mutate quickly, and can cause repeat infections. Therefore, doctors recommend that the general public and high-risk groups get an influenza vaccine once a year to prevent infection and reduce illness severity.
Those who have a persistent high fever that does not respond to antipyretic medication, extreme fatigue, severe headache, severe abdominal pain, are extremely restless, vomit frequently, cough constantly, and have marked difficulty breathing should seek immediate medical attention for a thorough influenza A diagnostic test and antiviral medication. Receiving proper treatment will help reduce the virus's spread, lower the risk of serious complications, and allow doctors to provide effective treatment and care promptly.
