In March 2009, an outbreak of “human swine flu” occurred in Mexico and spread rapidly around the world. The World Health Organization (WHO) initially called this type of influenza “human swine flu”, after it was renamed “influenza A (H1N1)”.
A. Pathogenesis
Influenza A (H1N1) virus belongs to the orthomyxoviridae (0rthomyxoviridae), influenza A virus genus (Influenza virus A). The virus is sensitive to ethanol, iodophor, tincture of iodine and other commonly used disinfectants; heat-sensitive, 30 minutes at 56 ℃ can be inactivated.
II. Epidemiology
(A) the source of infection.
Influenza A (H1N1) patients as the main source of infection, asymptomatic infected people are also infectious. There is no evidence of animal transmission of humans.
(B) the transmission route.
Mainly through droplet transmission through the respiratory tract, but also through the oral cavity, nasal cavity, eyes and other mucous membranes directly or indirect contact transmission. Contact with the patient’s respiratory secretions, body fluids and objects contaminated with the virus may also cause infection. Transmission through aerosols via the respiratory tract needs to be further confirmed.
(C) Susceptible population.
The population is generally susceptible.
(iv) High-risk groups that are more likely to become severe cases.
The following groups of people are more likely to develop severe cases after developing influenza-like symptoms.
1.Women during pregnancy;
2, with the following diseases or conditions: chronic respiratory disease, cardiovascular disease (except hypertension), kidney disease, liver disease, hematologic disease, neurological and neuromuscular diseases, metabolic and endocrine system diseases, immune suppression (including the application of immunosuppressants or HIV infection, etc. resulting in immune deficiency), long-term aspirin users under 19 years of age;
3, obese people (BMI ≥ 40 high risk, BMI in 30-39 may be a high risk factor);
4, children <5 years old (age <2 years are more likely to have serious complications);
5, the age of ≥ 65 years old elderly.
III. Clinical manifestations and auxiliary examinations
The incubation period is usually 1-7 days, mostly 1-3 days.
(A) Clinical manifestations.
Usually present with flu-like symptoms, including fever, sore throat, runny nose, nasal congestion, cough, sputum, headache, generalized aches and pains, and malaise. Some cases present with vomiting and/or diarrhea. A small number of cases have only mild upper respiratory symptoms without fever. Signs mainly include pharyngeal congestion and enlarged tonsils.
Complications such as pneumonia may occur. In a few cases, the disease progresses rapidly, with respiratory failure, multiple organ insufficiency or failure.
Exacerbation of the existing underlying disease may be induced, presenting the corresponding clinical manifestations.
Severe disease can lead to death.
(B) Laboratory tests.
1. Peripheral blood test: total white blood cell count is generally not high or reduced.
2. Blood biochemical examination: hypokalemia is observed in some cases, and creatine kinase, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase are elevated in a few cases.
3.Pathogenetic examination.
(1) viral nucleic acid detection: RT-PCR (preferably using real-time RT-PCR) method to detect respiratory specimens (pharyngeal swabs, nasal swabs, nasopharyngeal or tracheal extracts, sputum) in the nucleic acid of influenza A H1N1 virus, the results can be positive.
(2) virus isolation: respiratory specimens can be isolated from the influenza A H1N1 virus.
(3) serum antibody test: dynamic detection of double serum influenza A (H1N1) virus-specific antibody levels are 4-fold or more than 4-fold elevated.
(C) chest imaging.
Laminar shadows are seen in the lungs when combined with pneumonia.
IV. Diagnosis
Diagnosis is mainly combined with epidemiological history, clinical manifestations and pathogenic examination, early detection and diagnosis is the key to prevention, control and effective treatment.
(A) Suspected cases.
A suspected case can be diagnosed if one of the following conditions is met.
1, within 7 days before the disease and the infectious period of confirmed cases of influenza A (H1N1) have close contact, and the emergence of influenza-like clinical manifestations.
Close contact is not taken in the case of effective protection, consultation, care of the infectious period influenza A (H1N1) patients; living with patients; contact with the patient’s respiratory secretions, body fluids, etc..
2, within 7 days before the onset of influenza A (H1N1) epidemic (the emergence of sustained human transmission of the virus and community-based levels of epidemics and outbreaks) in the region, the emergence of influenza-like clinical manifestations.
3, the emergence of influenza-like clinical manifestations, positive test for influenza A virus, not yet further detection of virus subtypes.
For the above three cases, where conditions permit, arrangements can be made for pathogenic examination of influenza A (H1N1).
(B) clinical diagnosis of the case.
Limited to the following cases to make a clinical diagnosis: the same influenza A (H1N1) outbreak, without laboratory confirmation of influenza-like symptoms of cases, in excluding other influenza-like symptoms of disease, can be diagnosed as a clinical diagnosis of the case.
Influenza A (H1N1) outbreak is a short period of time in an area or unit with an abnormal increase in influenza-like cases, confirmed by laboratory tests for influenza A (H1N1) outbreak.
Where conditions permit, clinical diagnosis cases can be arranged for pathogenic testing.
(C) confirmed cases.
The presence of influenza-like clinical manifestations, along with one or more of the following laboratory test results.
1, positive nucleic acid test for influenza A (H1N1) virus (can be used real-time RT-PCR and RT-PCR methods);
2, the isolation of influenza A (H1N1) virus;
3, double serum influenza A (H1N1) virus-specific antibody levels were 4-fold or more than 4-fold elevated.
V. Serious and critical cases
(A) one of the following conditions for serious cases.
1, persistent high fever > 3 days;
2.Severe cough, coughing up pus or blood sputum, or chest pain;
3. Rapid respiratory rate, dyspnea, cyanosis of lips and mouth;
4.Mental changes: unresponsiveness, drowsiness, agitation, convulsions, etc;
5.Severe vomiting, diarrhea, and dehydration;
6. Imaging with signs of pneumonia;
7. Rapid increase in the level of cardiac enzymes such as creatine kinase (CK) and creatine kinase isoenzyme (CK-MB);
8. Significant aggravation of the original underlying disease.
(b) Critical cases are those with one of the following conditions.
1, respiratory failure;
2.Infectious toxic shock;
3.Multi-organ insufficiency;
4. Other serious clinical conditions that require monitoring and treatment.
VI. Principles of clinical classification and treatment
(A) suspected cases: isolated in a room with good ventilation. Hospitalized cases must do pathogenic examination of influenza A (H1N1).
(B) clinically diagnosed cases: in a well-ventilated room isolated. Inpatient cases must do pathogenic examination of influenza A (H1N1).
(C) confirmed cases: isolation in a well-ventilated room. Inpatient cases can be more than one person in the same room.
VII. Principles of hospitalization
According to the patient’s condition and the status of local medical resources, in accordance with the principle of priority of serious illness to arrange hospitalization.
(a) Prioritize the admission of serious and critical cases. For critical cases, according to the conditions of local medical facilities, timely transfer to the intensive care unit (ICU) with conditions of prevention and control for treatment.
(B) does not have the conditions for the treatment of serious and critical cases of medical institutions, to ensure medical safety under the premise of timely transfer of cases to hospitals with the conditions; the condition is not suitable for referral, the local health administrative departments or higher-level health administrative departments to organize experts in situ for active treatment.
(C) high-risk groups of people infected with influenza A (H1N1) are more likely to become serious cases, it is appropriate to arrange inpatient consultation and treatment. Such as the implementation of home isolation treatment, should be closely monitored, once the deterioration of the disease must be promptly arranged for inpatient consultation and treatment.
(D) mild cases can be arranged for home isolation observation and treatment.
VIII. Treatment
(a) General treatment.
Rest, drink more water, and closely observe changes in the condition; antipyretic treatment can be given to cases of high fever.
(B) antiviral treatment.
Studies have shown that such influenza A (H1N1) virus currently on the neuraminidase inhibitor oseltamivir (oseltamivir), zanamivir (zanamivir) sensitive to amantadine and amantadine resistance.
For clinical symptoms are mild and no comorbidities, the disease tends to self-limiting cases of influenza A (H1N1), no active application of neuraminidase inhibitors.
(C) other treatment.
1, such as the emergence of hypoxemia or respiratory failure, should be promptly given the appropriate therapeutic measures, including oxygen therapy or mechanical ventilation.
2.Give corresponding anti-shock treatment when combined with shock.
3.Give corresponding supportive treatment when other organ function damage occurs.
4. In case of combined bacterial and/or fungal infection, give corresponding antibacterial and/or antifungal drug treatment.
(D) Chinese medicine evidence-based treatment.
IX. Discharge criteria
1.The body temperature is normal for 3 days, other influenza-like symptoms basically disappear, and the clinical condition is stable, so the patient can be discharged.
2, due to underlying diseases or comorbidities heavier, requiring a longer hospitalization of influenza A (H1N1) cases, after the pharyngeal swab influenza A (H1N1) virus nucleic acid test turns negative, can be transferred from the isolation ward to the appropriate ward to do further treatment.