Seasonal Influenza
Seasonal Influenza is an RNA virus caused by infection with the Influenza Virus. It is a contagious disease that spreads widely and can be found throughout the year, especially during the rainy and winter seasons. The types of strains found in humans can be classified as types A, B, and C.
Types of Influenza
Type A is the most severe and dangerous. It can be transmitted from animal carriers to humans and from infected humans to others through coughing, sneezing, and airborne respiratory droplets containing the virus. Therefore, it can spread widely or cause global pandemics in a short time. The structure of type A virus differs from other types in that it has two glycoproteins: Hemagglutinin (HA) and Neuraminidase (NA). HA functions to bind to cell receptors and invade cells to produce new viral particles upon infection, while NA helps release newly formed viruses to spread to other cells. HA has 15 subtypes, and NA has 9 subtypes. Virus strains are named based on the combination of these proteins, such as strains that have caused outbreaks in recent decades like H1N1 (swine flu) and H5N1 (avian flu). The naming of type A influenza viruses uses the abbreviations H and N followed by numbers indicating the protein subtype, for example:
- H1N1 influenza virus strain (old strain) which caused the global pandemic in 1918-1919, resulting in approximately 20-40 million deaths. Since it originated from Spain, it was called the “Spanish flu” and re-emerged as a major outbreak in 1977 known as the “Russian flu” because it originated from Russia.
- New H1N1 influenza virus strain (2009 strain) caused a global pandemic in 2009. It is a mutated H1N1 strain composed of genetic material from swine, avian, and human influenza viruses. It is more severe than the old strain and originated from Mexico (the virus can spread from 1 day before symptoms appear, is most contagious during the first 3 days of illness, and may spread up to 7 days after illness onset).
- H2N2 influenza virus straincaused influenza outbreaks in Asia, resulting in about 1 million deaths, found in 1957-1958.
- H3N2 influenza virus straincaused influenza outbreaks in Hong Kong, resulting in about 700,000 deaths, found in 1968-1969.
- H5N1 influenza virus strainprimarily causes outbreaks in poultry. Recently, this strain has mutated to infect humans or mammals with high severity, causing death, known as Avian influenza. Fortunately, transmission to humans is not easy and requires close contact, and human-to-human transmission is rare, allowing control of this virus outbreak.
Type B virus usually spreads seasonally when weather conditions favor infection, such as in winter and rainy seasons. Seasonal flu may cause regional outbreaks.
Type C virus causes mild respiratory infections with minor or no symptoms and does not cause outbreaks.
Influenza in humans: can be divided into two major groups: seasonal influenza and new strains causing global pandemics.
- Seasonal influenza usually results from long-known influenza viruses. However, because the influenza virus constantly mutates, people who have had influenza before can get infected again if the virus changes. Symptoms are usually less severe due to some existing immunity.
- Pandemic influenza such as the 2009 new strain caused by the mutated H1N1 virus, which differs significantly from the original H1N1 virus, leaving most people without immunity and causing widespread infection.
The common cold (Cold) is an infection of the nose and throat, sometimes called upper respiratory tract infection (URI). It is caused by viruses collectively called Coryza viruses, mainly Rhinoviruses. Other viruses include Adenoviruses and Respiratory syncytial virus. When the virus enters the nose and throat, it causes nasal mucosa swelling and redness with mucus secretion. Patients experience runny nose and mild fever. Although it is a self-limiting disease resolving within one week, it is the most common reason for doctor visits. On average, children get colds 6-12 times per year, adults 2-4 times, women more often than men due to close contact with children, and elderly people may get it once a year.
Differences Between Cold and Influenza
Cold and influenza have very similar symptoms, but influenza symptoms are noticeably more severe.
|
Symptom |
Cold |
Influenza |
|
Fever |
Not high in adults; children may have fever |
High fever 38-40°C for 3-4 days |
|
Headache |
Rare |
Severe headache |
|
Body aches |
Mild |
Common and severe |
|
Weakness |
Mild |
May last 2-3 weeks |
|
Fatigue |
Not present |
Common |
|
Nasal congestion |
Common |
Occasional |
|
Sneezing |
Common |
Occasional |
|
Sore throat |
Common |
Occasional |
|
Cough, chest tightness |
Mild dry cough |
Common, sometimes severe |
|
Complications |
Sinusitis and middle ear infection |
Bronchitis and pneumonia |
|
Prevention |
None |
Vaccination; Amantadine or Rimantadine (antiviral drugs) |
|
Treatment |
Symptomatic treatment |
Amantadine or Rimantadine within 24-48 hours after symptom onset |
Transmission of the Common Cold
The virus is transmitted through the respiratory tract. Virus particles in the sputum, nasal mucus, and saliva of infected patients spread to others through direct coughing or sneezing or by inhaling droplets within 1 meter of the patient. Some may get infected indirectly through contaminated hands or objects. The virus enters the body through the nose, eyes, or mouth.
Symptoms of the Common Cold
The incubation period is about 1-4 days, averaging 2 days. Patients experience sudden fatigue, loss of appetite, nausea, severe headache, limb pain, joint pain, pain around the eye sockets, high fever of 39-40°C, sore throat with redness, runny nose, dry cough, and red eyes. Fever, nausea, and vomiting usually resolve within 2 days, but runny nose and nasal congestion may last up to 1 week. Severe symptoms often occur in the elderly or those with underlying diseases and may include pericarditis with chest pain, shortness of breath, meningitis with headache, drowsiness, unconsciousness, and pneumonia symptoms with severe breathing difficulty. Generally, influenza resolves within a few days, but some cases may have joint pain and cough lasting up to 2 weeks.
Contagious Period of the Common Cold
The contagious period refers to the time during which the virus can spread to others. It is 1 day before symptoms appear and 5 days after symptoms begin. In children, the virus may spread 6 days before symptoms and up to 10 days after.
Diagnosis of the Common Cold
Diagnosis of influenza relies on epidemiology, especially during outbreaks, and patient symptoms. Samples should be collected as soon as possible, within 3 days after symptom onset, using nasal swab, nasopharyngeal aspirate, or throat swab.
Treatment of the Common Cold
Most patients with influenza recover on their own. If symptoms are mild, home care is recommended. Care methods include:
- Rest and avoid exercise
- Drink electrolyte solutions or fruit juices; avoid excessive plain water to prevent electrolyte imbalance
- Symptomatic treatment: use a damp cloth to cool the body if feverish; if fever persists, take paracetamol. Aspirin is not recommended for those under 20 years old due to the risk of Reye syndrome. For severe cough, take cough medicine, but do not self-medicate young children. For sore throat, gargle with a glass of water mixed with 1 teaspoon of salt. Avoid forceful nose blowing as it may spread the infection.
- During outbreaks, avoid using public telephones, door handles, and public places
- Cover mouth and nose with a handkerchief when coughing or sneezing
When Should Patients See a Doctor?
Adults with influenza should see a doctor if they have the following symptoms:
- High fever lasting a long time
- Difficulty breathing or shortness of breath
- Chest pain or tightness
- Dizziness or fainting
- Vomiting and inability to eat
These Groups Are at Risk of Complications and Should See a Doctor When Having Influenza
- People with chronic diseases such as liver disease, heart disease, kidney disease, lung disease
- Pregnant women
- People over 65 years old
- Patients with AIDS
- Residents in nursing homes
Influenza Patients with These Symptoms Should Be Treated in Hospital
- Dehydration and inability to drink enough fluids
- Sputum mixed with blood
- Difficulty breathing or shortness of breath
- Lips turning purple or blue
- High fever with delirium
- Fever and cough persisting after recovery from cold
High-Risk Groups Include:
- People aged 65 years and older
- Patients with chronic diseases such as heart disease, lung disease, diabetes, cancer patients undergoing chemotherapy, kidney disease patients, and overweight individuals
- Pregnant women at 4 months gestation or more
- Children aged 6 months and older, especially school-aged children
- Personnel who have contact with the above groups, such as caregivers for the elderly, childcare providers, healthcare workers, and teachers
Because influenza viruses mutate annually and cross-protection between strains is not possible, vaccination is necessary every year to ensure effective disease prevention.
Hospital Treatment
Doctors will provide intravenous fluids for patients who cannot drink enough. These patients should receive Amantadine or Rimantadine to speed recovery and reduce disease severity. Treatment should start within 48 hours after fever onset and continue for 5-7 days. These drugs do not reduce complications. Decongestants should be given if there is nasal discharge. Antibiotics should not be given if there are no complications. Most patients recover in 2-3 days, fever resolves in 7 days, and fatigue may last 1-2 weeks.
Prevention
- Maintain good health to build strong immunity by exercising regularly and getting enough rest
- Eat nutritious food, vegetables, and fruits to provide sufficient nutrients and vitamins
- Wash hands frequently
- Avoid touching your mouth or rubbing your eyes with your hands
- Do not share personal items such as towels, handkerchiefs, or drinking glasses
- Avoid close contact with infected individuals
- Stay home when sick
- Cover mouth and nose with a cloth when coughing or sneezing
- If at risk, vaccination can prevent infection: currently covers 4 strains
Vaccination
The best prevention for influenza is vaccination, which is made from inactivated virus and administered once a year by injection in the arm. Immunity develops about 2 weeks after vaccination, providing protection against infection. Vaccination is recommended for the following groups:
- People over 65 years old
- People with 7 chronic diseases: chronic obstructive pulmonary disease, asthma, heart disease, stroke, kidney failure, diabetes, cancer patients undergoing chemotherapy
- Pregnant women over 4 months gestation during influenza outbreaks
- Children aged 6 months to 2 years
