Types of Viruses including Influenza Virus

Diagnosis Prevention and Treatment of  Influenza Virus Viral Fever

Influenza (referred to as influenza) is an acute respiratory infection caused by influenza virus. It is also a highly infectious and fast-transmitting disease. It is mainly transmitted through droplets in the air, person-to-person contact, or contact with contaminated items. Typical clinical symptoms are: rapid fever, general pain, marked fatigue and mild respiratory symptoms. Generally, the autumn and winter season is its high incidence period, and the complications and deaths caused by it are very serious. The disease is caused by influenza viruses and can be divided into three types: A (A), B (B) and C (C). Type A viruses often undergo antigen mutations, are highly contagious, spread rapidly, and are prone to widespread epidemics. A type H1N1 is also a type A. The disease is self-limiting, but it is easy to cause serious complications such as pneumonia and cause death in infants and young children, the elderly and patients with cardiopulmonary diseases.



English name:Influenza

Visiting department:Respiratory Medicine

Common causes:Caused by an influenza virus infection

Common symptoms:Headache, fever, runny nose, muscle soreness, fatigue, etc.


Way for spreading:Droplets, direct contact, contact with contaminated items


Table of Content

1 Cause

2 Clinical Manifestations

3 Inspection

4 Diagnosis

5 Complications

6 Treatment

7 Prognosis

8 Prevention

9 Care


What are the Common Causes of Influenza Virus caused Viral Fever?

Caused by influenza virus, the virus is not heat-resistant, inactivated at 100 ° C for 1 minute or 56 ° C for 30 minutes, and is sensitive to common disinfectants (1% formaldehyde, peroxyacetic acid, chlorine-containing disinfectants, etc.). Dry, vacuum dry or survive below -20 ° C. Among them, influenza A virus often undergoes antigen mutation, is highly contagious, causing viral fever, spreads rapidly and is prone to large-scale epidemics.


What are the Clinical Manifestation of Influenza Virus?

Incubation period

The incubation period is generally 1 to 7 days, and most of them are 2 to 4 days.


(1) Simple influenza usually has sudden onset, chills and high fever, body temperature can reach 39 ° C ~ 40 ° C, and it is often accompanied by systemic symptoms such as headache, sore muscles and joints, extreme fatigue, and loss of appetite, often with sore throat, dry cough, but Nasal congestion, runny nose and discomfort behind the sternum. The face was flushed, and the conjunctiva of the eye was slightly congested.

If there is no complication, it is a self-limiting process, and the body temperature gradually subsides more than 3 to 4 days after the onset, and systemic symptoms improve, but it usually takes 1 to 2 weeks for cough and physical recovery. Mild flu is similar to the common cold, with mild symptoms, which can be recovered in 2 to 3 days.

(2) Pneumonia type influenza is essentially complicated by influenza virus pneumonia, which is more common in the elderly, children, and people with original heart and lung disease. The main manifestations are persistent high fever, severe cough, hemoptysis or purulent sputum, shortness of breath, cyanosis, audible lungs and wet rales. A chest radiograph showed scattered floc shadows in both lungs. Sputum culture has no growth of pathogenic bacteria and can isolate influenza virus. Can die from respiratory failure.

(3) Toxic influenza manifests as severe symptoms such as high fever, shock, respiratory failure, central nervous system damage, and diffuse intravascular coagulation (DIC), with a high mortality rate.

(4) In addition to fever, gastrointestinal type flu is characterized by vomiting, abdominal pain and diarrhea. More children than adults. It can be restored in 2 to 3 days.

(5) Clinical manifestations of influenza in special populations:

i. Children flu is in the flu epidemic season. In general, healthy children infected with the influenza virus may show mild influenza. The main symptoms are fever, cough, runny nose, nasal congestion and sore throat, headache and a small part of myalgia, vomiting and diarrhea.

The clinical symptoms of influenza in infants and young children are often atypical, and febrile seizures can occur. Neonatal influenza is rare, but it is easy to be associated with pneumonia, and often has symptoms of sepsis, such as lethargy, milk rejection and apnea. In children, laryngitis, bronchitis, bronchitis, bronchiolitis, pneumonia, and gastrointestinal symptoms caused by influenza viruses are more common in adults.

ii. Elderly flu patients with flu over 65 years of age are elderly flu. Because the elderly often have primary diseases such as the respiratory system and cardiovascular system, the elderly are more severely infected with the influenza virus, the disease progresses faster, and the incidence of pneumonia is higher than that of young adults. Other system injuries include influenza virus Myocarditis caused by abnormal electrocardiogram, heart failure, acute myocardial infarction, may also be accompanied by encephalitis and poor blood glucose control.

iii. Influenza in pregnant women In addition to fever, cough and other manifestations after influenza virus infection in pregnant women in the mid-to-late pregnancy, pneumonia is prone to occur, dyspnea, hypoxemia and even acute respiratory distress syndrome can cause abortion, premature delivery, fetal distress and fetal death. Inside the palace. Can cause the exacerbation of the original underlying disease, and severe cases can lead to death.

iv. Immune-deficient population Influenza-deficient population, such as organ transplantation population, AIDS patients, and long-term immunosuppressants, have a significantly increased risk of developing severe influenza after being infected with the influenza virus. Due to the susceptibility to influenza virus pneumonia, fever can occur quickly after onset. Symptoms can be cough, dyspnea and cyanosis, with high mortality.


How can we make examination of Influenza Virus infection?

1. Peripheral blood test

The total number of white blood cells is generally not high or decreased, and lymphocytes are increased. Severe cases can also rise. If combined with bacterial infection, the total number of white blood cells and neutrophils will increase.

2. Blood biochemical examination

Hypokalemia occurred in some cases, and creatine kinase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatinine were elevated in a few cases.

3. Etiological examination

It mainly includes virus isolation, virus antigen, nucleic acid and antibody detection. Virus isolation is the main method for laboratory detection; virus antigen and nucleic acid detection can be used for early diagnosis; antibody detection can be used for retrospective investigation, but it has little significance for the early diagnosis of cases.

4. Imaging examination

Some patients may show signs of bronchial infection with increased bronchial texture. Severe patients may have pulmonary invasive lesions or pleural effusions, or even fuse into films.


How can we diagnose Influenza Virus based Viral Infection?

Diagnosis of Influenza: A diagnosis can be made based on the cause, clinical manifestations, and laboratory tests.

Etiological examinations: mainly including virus isolation, virus antigen, nucleic acid and antibody detection. Virus isolation is the “gold standard” for diagnosis of the disease.

Virus antigen and nucleic acid detection can be used for early diagnosis. Antibody detection can be used for retrospective investigation, but it has little significance for the early diagnosis of cases.


1. Virus nucleic acid detection

RT-PCR (preferably real-timeRT-PCR) is used to detect influenza virus nucleic acids in respiratory specimens (pharyngeal swabs, nasal swabs, nasopharyngeal or tracheal extracts, and sputum). Viral nucleic acid detection has the best specificity and sensitivity, and can quickly distinguish virus types and subtypes. Generally, results can be obtained within 4-6 hours.


2. Virus isolation and culture

Isolation of influenza virus from respiratory specimens. In influenza seasons, patients with negative rapid antigen diagnosis and immunofluorescence tests for influenza-like cases are also recommended for virus isolation.

3. Virus antigen test (quick diagnostic reagent test)

The rapid antigen detection method can use immunofluorescence to detect respiratory specimens (pharyngeal swabs, nasal swabs, nasopharyngeal or tracheal extracts of mucosal epithelial cells). Monoclonal antibodies are used to distinguish influenza A and B.

Generally, Get results in hours. There is also a colloidal gold test, which can generally obtain results in 10-30 minutes. The interpretation of the rapid test results should be combined with the patient’s epidemiological history and clinical symptoms: in the non-epidemic period, the positive screening result may be false positive. In the epidemic period, the negative screening test result may be false negative. These two in all cases, the use of RT-PCR or virus isolation culture should be considered for further confirmation.

4. Serological diagnosis

Detection of influenza virus-specific IgM and IgG antibody levels. The dynamic detection of IgG antibody levels during the recovery period is 4 times or more higher than the acute phase, which is of retrospective diagnostic significance.


What are the Complications with Influenza Virus based viral Infection?

(1) The incidence of bacterial pneumonia is 5 to 15%. The illness worsened 2 to 4 days after the onset of the flu, or worsened after the flu recovery period, with fever, severe cough, purulent sputum, dyspnea, wet snoring and signs of lung consolidation. The total number of peripheral blood leukocytes and neutrophils increased significantly, mainly Streptococcus pneumoniae and Staphylococcus aureus, especially methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae or Haemophilus influenzae.


(2) Pneumonia caused by other pathogenic infections includes chlamydia, mycoplasma, Legionella pneumophila, fungi (Aspergillus), etc. When pneumonia of influenza patients is not effective with conventional anti-infective treatment, the possibility of fungal infection should be considered.

(3) Rhinovirus, coronavirus, respiratory syncytial virus, parainfluenza virus, etc. are common in other viral pneumonia, which has a high incidence in patients with chronic obstructive pulmonary disease. This can make the disease worse, which is difficult to be clinically related to influenza.

Virus-induced pneumonia is different, and related pathogenic and serological tests can help differentiate diagnosis.


(4) Reye syndrome (Reye’s syndrome): This is occasionally seen in children under 14 years old, especially those who use salicylic acid antipyretic and analgesics such as aspirin.

Mainly manifested as neurological symptoms such as nausea, vomiting, drowsiness, coma, and convulsions after fever, liver enlargement, no jaundice and normal cerebrospinal fluid examination. The pathogenesis is unclear.


(5) Heart damage: Heart damage is uncommon, mainly myocarditis and pericarditis. It can be seen that creatine kinase is elevated and the electrocardiogram is abnormal, while troponin abnormalities are rare and can be recovered. Heart failure can occur in severe cases.


(6) Nervous system injuries include encephalomyelitis, transverse myelitis, aseptic meningitis, focal neurological dysfunction, acute infectious demyelinating polyradiculoneuropathy (Guillain Barre syndrome).


(7) Myositis and rhabdomyolysis syndrome are rare in influenza. The main symptoms are muscle weakness, renal failure and elevated CK.


What is the Treatment for Influenza Virus based viral infection?

1. General symptomatic treatment

Rest in bed, drink plenty of water, give a liquid or semi-liquid diet, suitable nutrition, supplement vitamins, gargle with warm water or warm saline after eating, keep mouth and nose clean, anti-infective treatment when systemic symptoms are obvious.

2. Principles of treatment

Early application of antiviral therapy. We must adhere to the principle of equal emphasis on preventive isolation and drug treatment, and focus on cause treatment and symptomatic treatment. The basic principles include early application of anti-influenza virus drugs, avoiding blind or inappropriate use of antibacterial drugs, strengthening supportive care, preventing and treating complications, and rational application of symptomatic drugs.

Anti-flu virus medication. Start anti-flu virus medications as early as 36 hours or 48 hours after onset. Although there are data indicating that neuraminidase inhibitors can also be effective after 48 hours of onset, most studies have proven that early treatment is more effective.

(1) Application indication

a) Recommended use:

i. All adults and children who are confirmed by laboratory etiology or highly suspected of influenza and have high risk factors for complications, regardless of the underlying disease, influenza vaccine immunity status and severity of influenza, should be within 48 hours of onset Give treatment.

ii. Laboratory confirmed or highly suspected influenza and adult and pediatric patients who need to be hospitalized, regardless of underlying disease, influenza vaccine immunity status, if the influenza virus test is positive 48 hours after onset, antiviral medication is also recommended.

b) Consider using:

i. Adults and children with flu outpatients suspected of having high-risk complications of influenza clinically, onset of illness> 48 hours without improvement, and positive specimens after 48 hours.

ii. Patients with high clinical suspicion or laboratory-confirmed influenza, no risk factors for complications 48 hours after onset can also benefit from antiviral therapy. However, there is no prospective study to evaluate its safety and efficacy.


(2) Specific drugs

a) The mechanism of neuraminidase inhibitors is to prevent the virus from being released from infected cells and invade neighboring cells, reduce the virus’s replication in the body, and have activity against influenza A and B. There are two varieties listed in our country, namely oseltamivir and zanamivir. Numerous clinical studies have shown that neuraminidase inhibitor treatment can effectively alleviate the symptoms of influenza patients, shorten the duration and length of hospital stay, reduce complications, save medical costs, and possibly reduce the mortality rate of some people, especially in the onset of 48 Use early in hours.

Oseltamivir is an oral dosage form approved for children and adults> 1 year old and children and adults aged 5 (UK) or 7 (US). Controlled studies have shown no difference in efficacy with oseltamivir. Occasionally can cause bronchospasm and allergic reactions. Be cautious in patients with basic diseases such as asthma, and other adverse reactions are less.

b) M2 ion channel blockers block the ion channel of influenza virus M2 protein, thereby inhibiting virus replication, but only inhibiting influenza A virus. Including two varieties of amantadine and amantadine. Nervous system adverse reactions include neuroticism, anxiety, inattention, and mild headache, which are more common in amantadine; gastrointestinal reactions include nausea and vomiting, which are mostly mild, and can quickly disappear after stopping treatment. These two drugs are prone to resistance

c) The dosage for children is the same as that for different courses of treatment for adults. In emergency situations, oseltamivir can be used for infants older than 3 months. Antiviral treatment should be performed even if the time exceeds 48 hours.

(3) Supportive treatment and prevention of complications

Pay attention to rest, drink plenty of water, increase nutrition, and give a digestible diet. The main supplement is vitamins. Rinse mouth with warm water or warm saline after eating to keep mouth and nose clean. Maintain water and electrolyte balance. Close observation, monitoring and prevention of treatment complications.

(4) Reasonable application of relevant drugs

Influenza is a common viral infectious disease. For the treatment of influenza virus, antibiotics have no effect. Therefore, antibiotics should not be used without signs of bacterial infection, otherwise it will easily cause double infection or drug-resistant bacteria. Use antibiotics promptly in the presence of secondary bacterial infections.

Because fever is a prominent symptom of influenza, the application of antipyretic agent aspirin can also lead to the occurrence of Reye’s syndrome, so it is easy to choose physical cooling when dealing with fever in patients with influenza, and try to avoid the application of large doses of aspirin.


What is the Prognosis for Influenza viral Fever?

The course of the flu is self-limiting. Patients without complications usually heal themselves within 5 to 10 days. However, hospitalization is required for severe infections or complications. The high-risk groups for severe cases are mainly the elderly, young children, pregnant women or people with chronic underlying diseases. A few severe cases can die due to respiratory or multiple organ failure.


How can we prevent Influenza Virus based viral infection?

Prevention of Influenza Virus: Seasonal influenza has a strong ability to spread from person to person, and active prevention and control is more important than limited effective treatments. The main precautions are as follows.

Strengthening publicity and education on personal hygiene knowledge

1. Maintain indoor air circulation, and avoid crowd gathering places during peak seasons.

2. Cough and sneeze should use paper towels, etc. to avoid the spread of droplets.

3. Always wash your hands thoroughly and avoid touching your mouth, eyes, and nose with dirty hands.

4. Seek medical attention if flu-like symptoms occur during the epidemic, reduce contact with others, and try to rest at home.

5. Influenza patients should be isolated from the respiratory tract for 1 week or until the main symptoms disappear. Patient utensils and secretions should be thoroughly disinfected.

6. Strengthen outdoor physical exercise to improve the body’s disease resistance.

7. The autumn and winter climate is changeable, pay attention to the addition and subtraction of clothes.

8. Prevention and control of outbreaks in institutions: When influenza has spread in the community, if two or more people have flu-like symptoms within 72 hours in the same institution, they should be vigilant and actively perform pathogenic testing. Once diagnosed, patients should be admitted to the hospital for treatment or home recuperation, personal hygiene, and try to avoid and reduce contact with others.

When it is confirmed as an outbreak in the institution, it shall be implemented in accordance with the relevant provisions of the Law on the Prevention and Control of Infectious Diseases and the Regulations on Public Health Emergencies.

When an outbreak of infection occurs in a hospital, measures such as isolation and protection shall be implemented in accordance with the relevant technical guidelines.

9. Influenza vaccination: Influenza vaccination is the most effective way to prevent influenza and its complications. The vaccine needs to be vaccinated every year for effective protection. The replacement of vaccine strains is determined by WHO based on the results of global surveillance. Priority vaccination population:

(1) People with a higher risk of complications after influenza:

i. Infants 6 to 59 months of age.

ii. 60 years old or older.

iii. Adults and children suffering from chronic respiratory disease, cardiovascular disease, kidney disease, liver disease, blood disease, metabolic disease and other diseases.

iv. Adults and children with immunosuppressive disease or immunocompromised function.

v. People who cannot take care of themselves and those who have difficulty in sputum excretion due to nervous system diseases and who have the risk of aspiration of upper respiratory tract secretions. vi. Long-term residents of nursing homes such as nursing homes.

vii. Pregnant women and women planning to become pregnant during the flu season.

Adolescents under the age of 18 who have been receiving aspirin therapy for a long time.

(2) Persons who have a greater chance of transmitting influenza virus to high-risk groups:

i. Medical and health care workers.

ii. Staff of nursing homes for chronic diseases such as nursing homes and nursing homes.

iii. Family members and caregivers who are at higher risk of complications after flu.

(3) Contraindications

i. Those who are allergic to egg protein or any vaccine.

ii. Moderate and severe acute fever.

iii. Those who have suffered Guillain-Barre syndrome.

iv. The doctor thinks that other people cannot get the flu vaccine.

(4) Vaccination method and timing

i. Children from 6 months to 9 years old who have never been vaccinated against influenza or received only 1 dose in the previous year should receive 2 doses at an interval of 4 weeks; thereafter, 1 dose should be given before the high influenza season . Other people take 1 dose per year.

ii. The inoculation route is intramuscular or deep subcutaneous injection. It is recommended that infants and young children choose intramuscular injection of the thigh.

iii. Vaccination should be started in most areas of China before October every year.

10. Antiviral drug prevention: Drug prevention is not a substitute for vaccination. It can only be used as an emergency temporary prevention measure for people with high risk of comorbidities who have not been vaccinated or have not acquired immunity after vaccination. Antiviral drugs that are sensitive to the epidemic strain should be selected as preventive drugs, and the course of treatment should be determined by the physician, usually 1 to 2 weeks.

For those who have been vaccinated but have immunosuppression due to various reasons, and it is difficult to obtain effective immune effects, whether to add antiviral drug prevention and timing, course of treatment, dosage, etc., should be determined by the physician.

(1) Ayurvedic Herbal or Chinese medicine prevention: those who have clear contact with influenza patients:

i. Children, young adults, strong people can use the following: honeysuckle, big green leaves, mint, raw licorice, decoction, one pair daily, for 5 days.

ii. The elderly and infirm can use the following: Codonopsis, Su Ye, Nepeta, decoction, one pair daily, for 5 days.

(2) Dietary attention: After suffering from influenza, you should eat a light diet and eat foods that are easy to digest and rich in vitamins. At the same time should pay attention to drink plenty of water, mainly boiled water.

Forbidden to eat salty foods: After eating salty foods, the mucosa of the diseased area is likely to contract, and nasal congestion is aggravated. Symptoms such as throat discomfort. And too salty food is easy to produce sputum, which stimulates local cough.

Fasting sweet and greasy foods: Sweetness can help wet, but greasy foods are not easy to digest, so patients with colds should avoid eating all kinds of sweets, drinks and fatty meat.

Fasting hot foods: Hot foods are easy to hurt Qi and burn, help fire sputum, make sputum difficult to cough, so it is not suitable for cold patients, especially onions must be eaten less.

It is not advisable to eat grilled and fried foods: the smell of such foods irritates the respiratory tract and digestive tract, which easily leads to contraction of the mucous membranes, worsens the condition, and is not easy to digest. Should also avoid tobacco and alcohol.



For hospitalized flu patients, caregivers should do the following:

1. You should be instructed to stay in bed during the fever period, drink plenty of water, regularly monitor your body temperature, and take Yinqiaojiedu tablets, Sangju cold tablets and other proprietary Ayurvedic and Chinese medicines or antiviral drugs.

2. For those who have systemic soreness or headache, they can assist the patient to take a comfortable position and give antipyretic analgesics when necessary.

3. Patients with pulmonary inflammation or cardiopulmonary insufficiency should closely monitor vital signs. Those who have difficulty breathing or cyanosis should take a semi-recumbent position, give oxygen, remove respiratory secretions in time, strengthen supportive treatment, pay attention to maintaining cardiovascular function, poisoning, etc. Significant symptoms can be treated with effective antibiotics or hormones.

4 Pairs of patients can be isolated by the respiratory tract until 48 hours after heat regression. The ventilation in the room should be strengthened. The patient’s respiratory tract secretions should be disinfected in time. The utensils, utensils and clothes can be sterilized by boiling or sun exposure.


In general, simple flu can be left without hospitalization, and home care can be performed according to the following aspects:

i. Place the patient in a single room to prevent the spread of droplets.

ii. The room must be well ventilated, and the air must be fumigated and disinfected regularly with vinegar. Wear a mask and disinfect the respiratory secretions and dirt (such as coughed sputum) of patients.

iii. Persons with high fever should be instructed to use physical cooling methods and proper use of antipyretics.

iv. Give nutrition and easy digestion For a light diet, patients should be encouraged to drink plenty of water to reduce the symptoms of poisoning and shorten the course of disease.

v. If the fever persists, cough, purulent sputum, or dyspnea should be sent to the hospital in a timely manner.




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NB The write-up is based on the most prevalent media information and is not a medical advice. Consult your Authorized Cardiologist for any Medical Treatment.

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