SARS is an inflammatory pathology of the lung tissue of viral etiology. It is characterized by increasing severe respiratory failure due to respiratory distress syndrome. The clinical picture also includes fever, dry cough, severe shortness of breath. Diagnosis is carried out using molecular genetic methods (identification of the pathogen) and serological studies (search for antibodies). The treatment of the disease is mainly pathogenetic and symptomatic, an etiotropic drug with proven viricidal efficacy has not been developed at present.
ICD 10
U04 Severe Acute Respiratory Syndrome (SARS), Atypical pneumonia
General information
SARS (severe acute respiratory syndrome, SARS, formerly atypical pneumonia) is an infectious pathology of the lower respiratory tract. For the first time, reports of the disease began to arrive from hospitals in Guangdong Province (China) in 2002. SARS quickly spread across the country, in Vietnam, Singapore, Hong Kong. By May 2003, the infection had spread to all continents, and WHO announced a pandemic of SARS. The causative agent – a new coronavirus – was discovered in April 2003. Elderly people were the most susceptible to infection, no gender difference was detected. A feature of this pandemic was a large number of nosocomial infections.
Causes
Characteristics of the blower
The causative agent of infection is the RNA–containing coronavirus SARS–CoV. It is a spherical microorganism with spiny outgrowths, tropism to the cells of the alveoli, liver, intestines, also kidneys, heart, eye. The reservoir of infection in the wild is bats, the source is a sick or asymptomatic carrier. The main route of transmission is airborne, also the transmission of the virus can be carried out by contact and much less often – by fecal-oral route.
Risk factors
The main risk factors: age over 65 years, immune deficiencies associated with HIV infection, cancer, taking systemic corticosteroids. The vulnerable group includes people with lung diseases, cardiovascular system, diabetes mellitus, obesity. There is a high probability of illness in medical workers, persons caring for patients at home.
Pathogenesis
When they get on the mucous membrane of the mouth and nasopharynx, coronaviruses colonize the epithelium. They have different mechanisms of communication with receptors. Thus, interaction with epithelial cells occurs through aminopeptidase. The leading role in the mechanism of binding to human cell receptors belongs to the glycoprotein of the spiny processes. The released virions are able to re-sorb on the cell surface, causing their fusion and stimulating the host’s immune response.
The main target cells are alveolar epithelial cells, macrophages. Coronaviruses, having the ability to induce apoptosis, cause necrosis of the affected tissues. Inducing cell fusion has a strong effect on their permeability, leads to disruption of the water-salt balance and protein transport. In these conditions, surfactant insufficiency develops, symptoms of pulmonary distress syndrome occur.
Symptoms
The first symptoms of severe acute respiratory syndrome occur after the incubation period, which is 5 days (from 2 to 10 days). Usually, patients complain of a flu-like syndrome: fever over 38.5 ° C, chills, headache. There is marked weakness, muscle pain, decreased performance. By the end of the first week of the disease or by the beginning of the second, a dry, painful cough appears, which usually bothers patients at night with coronavirus infection.
The most formidable manifestation of SARS is shortness of breath. Patients note a growing feeling of lack of air, especially at night, when talking or straining, difficulty both inhaling and exhaling. Later, patients are forced to take a pose with support on their hands, breathing becomes hoarse, noisy, the skin acquires a purplish-bluish hue. In parallel, tickling, dry throat, and diarrhea symptoms may occur.
Complications
The most frequent complications of SARS occur due to progressive respiratory failure. The most serious consequences are pulmonary embolism, myocarditis, pericarditis, spontaneous pneumothorax, heart failure and cardiac arrhythmias. Repeated pneumonia, fibrous changes in the lungs are also observed. There are reports of the detection of coronaviruses in the cerebrospinal fluid in patients with multiple sclerosis.
Diagnostics
Diagnosis of coronavirus infection, its treatment is carried out jointly by infectious diseases doctors, pulmonologists, resuscitators. Other medical specialists are involved according to indications. It is important to collect an epidemiological history, including data on travel to endemic areas, family and work contacts of the patient. The main clinical, instrumental and laboratory methods of SARS diagnosis:
- Physical examination. Objectively, the symptoms of respiratory insufficiency are determined in patients – shortness of breath, forced position, bluish skin tone. There is an unproductive cough and an increase in body temperature. With auscultation of the lungs – weakening of breathing, shallow bubbly wheezing, dulling of percussion sound. Saturation in patients with pulse oximetry decreases to 90-70%.
- Laboratory tests. There are no specific changes. A general clinical blood test usually reveals lymphopenia, thrombocytopenia, acceleration of ESR. When bacterial complications are added, leukocytosis develops. In biochemical studies, there is an increase in the activity of CRP, LDH, transaminases. It is possible to prolong the APTT, hyponatremia, hypokalemia, also hypocalcemia, hypomagnesemia.
- Identification of infectious agents. The diagnosis is verified using the PCR method (RT PCR SARS-CoV). The material for the isolation of coronavirus is a smear from the nasopharynx, sputum, blood plasma, during recovery – feces. Serological examination (ELISA) is carried out in paired sera no earlier than 4 days of the disease, cross-reactions with other types of coronaviruses are possible.
- Instrumental methods. Chest CT is recommended. Already on the 3-4 day of the disease, typical manifestations of SARS occur: first peripheral unilateral, then bilateral multiple drain infiltrates in the form of “frosted glass”. In the late stages of infection, pneumothorax, pneumomediastinum, subpleural fibrosis may be detected. Dynamic CT examination in infected patients is necessary.
Differential diagnosis
Similar clinical symptoms are observed in influenza, respiratory syncytial viral pathology, MERS, which requires their laboratory verification. It is necessary to differentiate the SARS with pneumonia caused by Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia species, rarely Legionella species, Toxiella burnetii, Pneumococcus. Differential diagnosis is carried out with COPD, bronchiectatic disease, anaphylaxis.
Treatment
The symptoms of SARS detected in a patient are an indication for hospitalization, with the exception of mild cases when outpatient treatment is allowed in compliance with the rules of self-isolation, mandatory medical monitoring of the condition. Hospitals should be equipped with intensive care wards, intensive care units. There is no specific diet, the drinking regime is not limited to contraindications.
Conservative therapy
There is no standardized treatment for SARS. Symptomatic therapy is preferred: antipyretics, surfactant preparations, detoxification and other means. The use of systemic corticosteroids increases the risk of nosocomial infections ‒ disseminated fungal diseases, metabolic disorders, osteonecrosis. These drugs, prescribed in the early stages of SARS, can prolong viremia.
The SARS virus is prone to nosocomial spread, so the use of nebulizers, spacers and oxygen therapy through nasal catheters or a mask should be prohibited or strictly limited. With an increase in respiratory failure, respiratory symptoms of distress syndrome, the patient is transferred to a ventilator. According to the indications, ECMO is used.
Experimental treatment
Treatment using ribavirin has not proven to be effective in a retrospective study. The use of high doses of the drug led to a documented decrease in hemoglobin in 59% of patients, hemolysis was recorded among 36% of patients, hepatotoxic, cardiotoxic effects were noted. The combination with lopinavir / ritonavir reduced the frequency of intubation, as well as overall mortality to 2.3%.
Lopinavir, boosted with ritonavir, is a drug for the treatment of HIV infection. Treatment with the introduction of this drug for SARS showed a decrease in the viral load of the coronavirus, allowed to reduce the dose of methylprednisolone. Interferon alfakon-1 also had an inhibitory effect on the pathogen, but the study was conducted on only 9 patients, was accompanied by corticosteroids and was not controlled.
Treatment with passive immunization using plasma of recovered patients was used on a small number of patients, but had the effect of significantly reducing mortality compared to placebo or lack of therapy. The best results were obtained in the group of infected SARS, who were injected with plasma no later than the 14th day of the disease. The concept of human monoclonal antibodies was also proposed.
Prognosis and prevention
The prognosis with timely detection, absence of somatic decompensated pathology is favorable. The mortality rate of SARS is about 4%, varies from 0 to 40% depending on the initial condition of the patient. A specific prevention (vaccine) is under development. Non–specific measures: the use of masks by the sick, frequent hand washing with soap, cough etiquette, strict compliance with sanitary standards in medical institutions.