Overview of the coronavirus

  • Epidemiology



    Coronavirus infections are distributed in many parts of the world. The existence of this virus has been found in China, the United Kingdom, the United States, Germany, Japan, Russia, Finland, India and other countries. Infections caused by the virus mainly occur in winter and early spring. In a home inspection in Michigan, the United States, it was proved that the coronavirus can infect all age groups, 0-4 years old accounted for 29.2%, 40 years old and above accounted for 22%, and the incidence rate was highest in the 15-19 year old age group. This is different from the prevalence of other upper respiratory viruses, such as respiratory syncytial virus, which mostly decreases with age. In addition, rhinoviruses are not common when the coronavirus is prevalent.

    So far, about 15 different coronavirus strains have been discovered, which can infect a variety of mammals and birds, and some can cause illness in humans.

    Human diseases caused by coronavirus are mainly respiratory infections (including severe acute respiratory syndrome, SARS). The virus is very sensitive to temperature and grows well at 33°C, but it is inhibited at 35°C. Due to this characteristic, winter and early spring are the epidemic seasons of the virus disease. Coronavirus is one of the main pathogens of the common cold in adults. The infection rate in children is relatively high, mainly due to upper respiratory tract infections, and generally rarely affects the lower respiratory tract. In addition, it can also cause acute gastroenteritis in infants and newborns. The main symptoms are watery stools, fever, and vomiting, which can be pulled more than 10 times a day. In severe cases, bloody stools may occur. In rare cases, it can also cause nervous system syndromes. .

    Coronavirus is also an important pathogen of acute exacerbation of chronic bronchitis in adults. Studies have shown that the coronavirus that caused atypical pneumonia in many countries and regions around the world is not the two known types. Just like outsiders’ speculation, it is a new type of virus that has never been exposed to humans. Previously, some experts believed that it was a "paramyxovirus group" or "interstitial pneumonia virus", but it was eventually overturned due to insufficient evidence.

    The virus grows in epithelial cells, and can also infect the liver, kidney, heart, and eyes. It can also grow in other cell types (such as macrophages). There is no suitable animal model of human coronavirus for research (animal model of human disease) refers to animals with simulated performance of human disease established in various medical scientific researches. Animal disease models are mainly used in the research of experimental physiology, experimental pathology and experimental therapeutics (including new drug screening), the nasal mucosal cells infected by coronavirus can only be isolated by organ culture. It is also very difficult to use the above-mentioned materials to propagate viruses.

    The serotype and antigenic variability of coronavirus are not yet clear. Coronavirus can be reinfected, indicating that there are multiple serotypes (at least 4 known) and antigenic mutations, and its immunity is difficult, and there are no specific preventive and therapeutic drugs.


    Clinical features

    Coronavirus is one of the main pathogens of the common cold in adults. It can cause upper respiratory tract infections in children and rarely spreads to the lower respiratory tract. The incubation period of coronavirus infection is generally 2 to 5 days, with an average of 3 days. A typical coronavirus infection presents cold symptoms such as runny nose and malaise. Different types of viruses have different virulence and cause different clinical manifestations. The symptoms caused by the OC43 strain are generally more serious than those caused by the 229E virus. Coronavirus infection can cause symptoms such as fever, chills, and vomiting. The course of the disease is generally about 1 week, the clinical course is mild, and there are no sequelae.

    Coronavirus can also cause acute gastroenteritis in infants and neonates. The main symptoms are watery stools, fever, and vomiting, more than 10 times a day. In severe cases, bloody stools can occur.

    The literature reports that coronavirus infection can produce the following clinical symptoms:

    (1) Respiratory system infection, including severe acute respiratory syndrome (SARS);

    (2) Intestinal infection (occurring occasionally in infants);

    (3) Nervous system symptoms (rarely).

    Coronavirus is excreted from the body through respiratory secretions and is transmitted through oral fluids, jets, and contact. Clinically, most coronaviruses cause mild and self-healing diseases, but a few may have neurological complications.

    Common human coronaviruses (including 229E, NL63, OC43, and HKU1) usually cause mild or moderate upper respiratory tract diseases, such as colds. Symptoms mainly include runny nose, headache, cough, sore throat, fever, etc. Sometimes it can cause lower respiratory tract diseases such as pneumonia or bronchitis. It is more common in patients with heart and lung diseases, people with weakened immune systems, infants and the elderly.

    MERS-CoV and SARS-CoV often cause more severe symptoms. MERS symptoms usually include fever, cough, and shortness of breath, and even develop into pneumonia. The case fatality rate is about 34.4%. SARS symptoms usually include fever, chills and body pain, and even develop into pneumonia, with a fatality rate of about 9.6%.


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