What Factors Can Cause an Influenza Outbreak?

Influenza (referred to as influenza) is an acute respiratory infection caused by influenza virus. It is also a highly contagious 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: high 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 virus and can be divided into three types: A (A), B (B), and C (C). Type A viruses often undergo antigen mutation, are highly infectious, spread rapidly, and are prone to large-scale 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.

Basic Information

nickname: influenza
English name: influenza
Visiting department: Respiratory Medicine

Common causes: Caused by an influenza virus infection
Common symptoms: Headache, fever, runny nose, sore muscles, fatigue, etc.
Contagious: Have
way for spreading: Droplets, direct contact, contact with contaminated items

Causes of influenza

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, spreads rapidly, and is prone to large-scale epidemics.

Clinical manifestations of influenza

Incubation period

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

Performance

(1) Simple influenza usually has sudden onset, chills and high fever, body temperature can reach 39 ° C to 40 ° C, and is often accompanied by systemic symptoms such as headache, sore muscles and joints, extreme fatigue, and loss of appetite. Nasal congestion, runny nose, and discomfort behind the sternum. The face was flushed, and the conjunctiva of the eye was slightly congested. If there are no complications, it is a self-limiting process. After 3 to 4 days of onset, the body temperature gradually subsides and systemic symptoms improve. However, 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. The 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 influenza is characterized by vomiting, abdominal pain, and diarrhea. There are more children than adults. It can be recovered in 2 to 3 days.

(5) Clinical manifestations of influenza in special populations 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, sore throat, and headache, and a small part of myocardial pain, 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. 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. Influenza in pregnant women In addition to flu, cough and other manifestations after infection with influenza virus in pregnant women, prone to pneumonia, rapid dyspnea, hypoxemia, and even acute respiratory distress syndrome can cause abortion, premature delivery, fetal distress and fetal death. Inside the palace. Can cause the aggravation of the original underlying disease, and severe cases can lead to death. 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 influenza virus. Because of influenza virus pneumonia, fever can occur quickly after the onset , Cough, dyspnea and cyanosis, high mortality.

Influenza check

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 occurs in some cases, and creatine kinase, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatinine are elevated in a few cases.

3. Etiology related inspection

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.

Influenza diagnosis

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.

Virus nucleic acid detection

RT-PCR (preferably real-timeRT-PCR) method is used to detect influenza virus nucleic acid in respiratory specimens (pharyngeal swab, nasal swab, nasopharyngeal or tracheal extract, 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, virus-free isolation is also recommended for patients with rapid antigenic diagnosis of influenza-like cases and negative for immunofluorescence.

3. Viral antigen detection (quick diagnostic reagent detection)

The rapid antigen detection method can use immunofluorescence to detect respiratory specimens (pharyngeal swabs, nasal swabs, nasopharyngeal or tracheal extracts of mucosal epithelial cells), and 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 in the recovery period is 4 times or more higher than in the acute phase, which is of retrospective diagnostic significance.

Influenza complications

(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 pulmonary consolidation. The total number of peripheral blood leukocytes and neutrophils increased significantly, mainly S. pneumoniae and S. aureus, especially methicillin-resistant S. aureus, S. pneumoniae, or Haemophilus influenzae.

(2) Pneumonia caused by other pathogenic infections includes chlamydia, mycoplasma, Legionella pneumophila, fungi (Aspergillus), etc. When pneumonia in 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, and can make the disease worse, which is difficult to be clinically related to influenza. Different from pneumonia caused by the virus, related pathogenic and serological tests can help differentiate diagnosis.

(4) Reye syndrome (Reye's syndrome) 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 injuries are 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.

Influenza treatment

1. General symptomatic treatment

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

2. Principles of treatment

Early application of antiviral therapy. It is necessary to adhere to the principle of equal emphasis on prevention isolation and drug treatment, and on cause therapy and symptomatic treatment. Basic principles include early application of anti-influenza virus drugs, avoiding the 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 data indicate 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

1 Recommended use 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. 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 drugs are also recommended.

2) Consider using. Adults and children with flu out-patients who are suspected of having high-risk complications of influenza clinically, whose illness is not improved after 48 hours, and whose specimens are positive after 48 hours. Patients with high clinical suspicion or laboratory-confirmed influenza, no risk factors for complications, and 48 hours after onset can also benefit from antiviral therapy, but their safety and efficacy have not been evaluated prospectively.

(2) Specific drugs

1) 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 in 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 5 years (UK) or 7 years (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.

2) 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. Neurological 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 disappear quickly after stopping the drug. These two drugs are prone to resistance

3) The dosage for children is the same as that for adults in different courses. In emergencies, 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 related 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 the generation of drug-resistant bacteria. Use antibiotics promptly in the presence of secondary bacterial infections. Since fever is a prominent symptom of the flu, the application of aspirin, an antipyretic agent, can also lead to the occurrence of Reye's syndrome, so it is easy to choose physical cooling when dealing with fever in flu patients, and try to avoid the application of large doses of aspirin.

Influenza prognosis

The course of the flu is self-limiting, and patients without complications usually heal themselves within 5 to 10 days. However, serious infections or complications require hospitalization; the high-risk groups of severe cases are mainly elderly, young children, pregnant women or those with chronic underlying diseases; a few severe cases can die from respiratory or multiple organ failure.

Influenza prevention

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 climate of autumn and winter is changeable, pay attention to adding or subtracting 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 conduct pathogenic testing. Once diagnosed, patients should be required to be admitted to hospital for treatment or home recuperation, and good personal hygiene to avoid and minimize contact with others. When confirmed as an outbreak in an 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 a hospital infection occurs, measures such as isolation and protection should 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 infants 6 to 59 months of age. 60 years old or older. Adults and children suffering from chronic respiratory disease, cardiovascular disease, kidney disease, liver disease, blood disease, metabolic disease and other diseases. Adults and children with immunosuppressive disease or immunocompromised function. People who cannot take care of themselves and those who have difficulty in sputum excretion due to nervous system diseases and who are at risk of aspiration due to upper respiratory secretions. Long-term residents of nursing homes such as nursing homes. Pregnant women and women planning to become pregnant during the flu season. Adolescents under 18 years of age receive long-term aspirin treatment.

(2) Persons who have a greater chance of transmitting influenza virus to high-risk groups Medical and health care workers. Staff of nursing homes for chronic diseases such as nursing homes and nursing homes. Family members and caregivers who are at higher risk of complications after the flu.

(3) Contraindications Those who are allergic to egg protein or any vaccine. moderate and severe acute fever. Those who have suffered Guillain-Barre Syndrome. The doctor thinks that other people cannot get the flu vaccine.

(4) Vaccination methods and timing Children 6 months to 9 years old who have never been vaccinated against influenza or had received only 1 dose in the previous year should receive 2 doses at intervals of 4 weeks; thereafter, 1 dose should be given every year before the high influenza season . Other people take 1 dose per year. The inoculation route is intramuscular or deep subcutaneous injection. It is recommended that infants and young children choose intramuscular injection of the thigh. 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 caused 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 judged by the physician.

(1) Chinese medicine prevention: those who have clear contact with influenza patients: Children, young adults, strong people can use the following: honeysuckle, green leaves, mint, raw licorice, decoction, one pair daily, for 5 days . The elderly and frail 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 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 mucous membrane of the diseased area is likely to contract and aggravate nasal congestion. Sore throat symptoms. 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 mucosa, exacerbates the condition, and is not easy to digest. Should also avoid tobacco and alcohol.

Influenza care

For hospitalized flu patients, caregivers should do the following:

1. During the fever period, you should be instructed to stay in bed, drink plenty of water, regularly monitor your body temperature, and take Yinqiaojiedu tablets, Sangju cold tablets and other proprietary Chinese medicines or antivirals;

2. For those who have soreness or headache in the whole body, they can assist the patient to take a comfortable position, and if necessary, take antipyretic and analgesics;

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. 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, ventilation should be strengthened in the room, the patient's respiratory tract secretions should be disinfected in time, and utensils, utensils and clothing 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: Place the patient in a single room to prevent the spread of droplets; The room must be well ventilated, and the air must be fumigated and disinfected regularly with vinegar. Wear a mask to disinfect the respiratory secretions and dirt (such as coughed sputum) of patients; Persons with high fever should be instructed to use physical cooling methods and proper use of antipyretics; Give nutrition and easy digestion For a light diet, patients should be encouraged to drink more water to reduce the symptoms of poisoning and shorten the course of disease; If the fever persists, cough, purulent sputum, or dyspnea should be sent to the hospital in a timely manner.