Coronavirus disease 2019 is an infectious disease caused by Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease was first identified in 2019 in Wuhan , China, and has since spread globally, resulting in the 2019-20 coronavirus pandemic.
Signs and symptoms:
Although those infected with the virus may be asymptomatic, many develop flu-like symptoms including fever, cough, and shortness of breath. Less commonly, upper respiratory symptoms such as sneezing, runny nose, or sore throat may be seen. Gastorintestinal symptoms such as nausea, vomiting, and diarrhoea are seen in a minority of cases.In some, the disease may progress to pneumonia, multi-organ failure, and death.
As is common with infections, there is a delay from when a person is infected with the virus to when they develop symptoms, know as the incubation period.
The incubation period for COVID-19 is typically five to six days but may range from two to 14 days.
Mild cases typically recover within two weeks, while those with severe or critical disease may take three to six weeks to recover. Among those who have died, the time from symptom onset to death has ranged from two to eight weeks.
Course and complications:
The severity of COVID-19 varies. The disease may take a mild course with little or no symptoms, resembling other common upper respiratory diseases such as the common cold. However, in some COVID-19 may affect the lungs causing pneumonia. In those most severely affected, COVID-19 may rapidly progress to acute respiratory distress syndrome (ARDS) causing respiratory failure, septic shock, or multi-organ failure.Complications associated with COVID-19 include sepsis, abnormal clotting, and damage to the heart, kidneys, and liver. Clotting abnormalities, specifically an increase in the time required for the blood to clot (prothrombin time) have been described in 6% of those admitted to hospital with COVID-19, while abnormal kidney function is seen in 4% of this group.
Blood markers of damage to the heart (Troponin I) are increased in more than 50% of severe cases of COVID-19, and abnormal heart rhythms leading to cardiac arrest have been described. Liver injury as shown by blood markers of liver damage is frequently seen in severe cases, although liver failure has not been described as of March 2020.
Several factors predict the severity of COVID-19 infection. Children are likely to have milder symptoms and a much lower chance of severe disease than adults. Older age and a high SOFA score (a clinical scoring scale assessing function of various metabolic systems and organs, e.g. lungs, heart, liver, kidneys, etc.) are associated with a worse prognosis.
Those with pre-existing heart conditions are at greater risk of cardiac complications. Blood tests associated with more severe disease include d-dimer greater than 1 μg/mL on admission; elevated levels of blood interleukin-6, high-sensitivity cardiac troponin I, lactate dehydrogenase; and abnormally low levels of lymphocytes (a type of white blood cell).
Cause:
The disease is caused by the virus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), previously referred to as the 2019 novel coronavirus (2019-nCoV).
It is primarily spread between people via respiratory droplets from coughs and sneezes.(The virus has been found in the feces of infected persons, but whether transmission through feces is possible is unknown.)
The lungs are the organs most affected by COVID-19 because the virus accesses host cells via the enzyme ACE2, which is most abundant in the type II alveolar cells of the lungs.
The virus uses a special surface glycoprotein, called "spike", to connect to ACE2 and enter the host cell. The density of ACE2 in each tissue correlates with the severity of the disease in that tissue and some have suggested that decreasing ACE2 activity might be protective, though another view is that increasing ACE2 using Angiotensin II receptor blocker medications could be protective and that these hypotheses need to be tested. As the alveolar disease progresses, respiratory failure might develop and death may follow.
ACE2 might also be the path for the virus to assault the heart causing acute cardiac injury. People with existing cardiovascular conditions have the worst prognosis.
The virus is thought to have an animal origin, through spill over infection. It was first transmitted to humans in Wuhan, China, in November or December 2019, and the primary source of infection became human-to-human transmission by early January 2020.On 14 March 2020, South China Morning Post reported that a 55-year-old from Hubei province could have been the first person to have contracted the disease on 17 November 2019.As of 14 March 2020, 67,790 cases and 3,075 deaths due to the virus have been reported in Hubei province; a case fatality rate (CFR) of 4.54%. Diagnosis:
The WHO has published several testing protocols for the disease. The standard method of testing is real-time reverse transcription polymerase chain reaction (rRT-PCR).
The test can be done on respiratory samples obtained by various methods, including a nasopharyngeal swab or sputum sample. Results are generally available within a few hours to two days.
Blood tests can be used, but these require two blood samples taken two weeks apart and the results have little immediate value.
Chinese scientists were able to isolate a strain of the coronavirus and publish the genetic sequence so that laboratories across the world could independently develop polymerase chain reaction (PCR) tests to detect infection by the virus.
As of 26 February 2020, there were no antibody tests or point-of-care tests though efforts to develop them are on going.
Diagnostic guidelines released by Zhongnan Hospital of Wuhan University suggested methods for detecting infections based upon clinical features and epidemiological risk.
These involved identifying people who had at least two of the following symptoms in addition to a history of travel to Wuhan or contact with other infected people: fever, imaging features of pneumonia, normal or reduced white blood cell count, or reduced lymphocyte count. A study published by a team at the Tingyi Hospital in Wuhan on 26 February 2020 showed that a chest CT scan for COVID-19 has more sensitivity (98%) than the polymerase chain reaction (71%). False negative results may occur due to PCR kit failure, or due to either issues with the sample or issues performing the test. False positive results are likely to be rare.
One study in China found that CT scans showed ground-glass opacities in 56%, but 18% had no radiological findings.Bilateral and peripheral ground glass opacities are the most typical CT findings. Consolidation, linear opacities and reverse halo sign are other radiological findings. Initially, the lesions are confined to one lung, but as the disease progresses, indications manifest in both lungs in 88% of so-called "late patients" in the study group (the subset for whom time between onset of symptoms and chest CT was 6–12 days) Prevention:
Because a vaccine against SARS-CoV-2 is not expected to become available until 2021 at the earliest, a key part of managing the COVID-19 pandemic is trying to decrease the epidemic peak, known as flattening the epidemic curve through various measures seeking to reduce the rate of new infections.
Slowing the infection rate helps decrease the risk of health services being overwhelmed, allowing for better treatment of current cases, and provides more time for a vaccine and treatment to be developed.
Preventive measures to reduce the chances of infection in locations with an outbreak of the disease are similar to those published for other coronaviruses: stay home, avoid travel and public activities, wash hands with soap and hot water often, practice good respiratory hygiene and avoid touching the eyes, nose, or mouth with unwashed hands. Social distancing strategies aim to reduce contact of infected persons with large groups by closing schools and workplaces, restricting travel, and cancelling mass gatherings.
According to the WHO, the use of masks is only recommended if a person is coughing or sneezing or when one is taking care of someone with a suspected infection.
To prevent transmission of the virus, the Centers for Disease Control and Prevention (CDC) in the United States recommends that infected individuals stay home except to get medical care, call ahead before visiting a healthcare provider, wear a face mask when exposed to an individual or location of a suspected infection, cover coughs and sneezes with a tissue, regularly wash hands with soap and water and avoid sharing personal household items.
CDC also recommends that individuals wash hands often with soap and water for at least 20 seconds, especially after going to the toilet or when hands are visibly dirty, before eating and after blowing one's nose, coughing, or sneezing. It further recommended using an alcohol-based hand sanitizer with at least 60% alcohol, but only when soap and water are not readily available.
The WHO advises individuals to avoid touching the eyes, nose, or mouth with unwashed hands. Spitting in public places also should be avoided.
Management:
There are no specific antiviral medications. People are managed with supportive care such as fluid and oxygen support, while at the same time, there is monitoring and supporting other affected vital organs. The WHO and Chinese National Health Commission have published treatment recommendations for taking care of people who are hospitalised with COVID-19.
Steroids such as methylprednisolone are not recommended unless the disease is complicated by acute respiratory distress syndrome.Intensivists and pulmonologists in the US have compiled treatment recommendations from various agencies into a free resource, the IBCC.
CDC recommends that those who suspect they carry the virus wear a simple face-mask.
The use of extracorporeal membrane oxygenation (ECMO) has been utilized to address the issue of respiratory failure, but its benefits are still under consideration
Personal protective equipment
Management of people infected by the virus includes taking precautions while applying therapeutic manoeuvres, especially when performing procedures like intubation or hand ventilation that can generate aerosols.CDC outlines the specific personal protective equipment and the order in which healthcare providers should put it on when dealing with someone who may have COVID-19:
1) gown,
2) mask or respirator,
3) goggles or a face shield, 4) gloves.
Mechanical ventilation
Most cases of COVID-19 are not severe enough to require mechanical ventilation (artificial assistance to support breathing), but a percentage of cases do. This is most common in older adults (those older than 60 years and especially those older than 80 years).This component of treatment is the biggest rate-limiter of health system capacity that drives the need to flatten the curve (to keep the speed at which new cases occur and thus the number of people sick at one point in time lower).
One study in China found 5% were admitted to intensive care units, 2.3% needed mechanical support of ventilation, and 1.4% died.
Experimental treatment
Antiviral medication may be tried in people with severe disease.The WHO recommended volunteers take part in trials of the effectiveness and safety of potential treatments.
There is tentative evidence for remdesivir as of March 2020. Lopinavir/ritonavir is also being studied in China.Nitazoxanide has been recommended for further in vivo study after demonstrating low concentration inhibition of SARS-CoV-2.
Chloroquine, normally used to treat malaria, was being trialled in China in February 2020, with preliminary results that seem positive.
Chloroquine phosphate has a wide range of antiviral effects and had been proposed as a treatment for SARS-CoV-2. In vitro tests have shown that it can inhibit the virus and the Guangdong Provincial Department of Science and Technology and the Guangdong Provincial Health and Health Commission issued a report stating that chloroquine phosphate "improves the success rate of treatment and shortens the length of patient’s hospital stay" and recommended it for people diagnosed with mild, moderate and severe cases of novel coronavirus pneumonia.
Tocilizumab has been included in treatment guidelines by China's National Health Commission after a completed small study by the University of Science and Technology of China.
The medication is undergoing testing in five hospitals in Italy after showing positive results in people with severe disease.Combined with a serum ferritin blood test to identify cytokine storms, it is meant to counter such developments, which are thought to be the cause of death in some affected people.
The interleukin-6 receptor antagonist was approved by the FDA for treatment against cytokine release syndrome induced by a different cause, CAR T cell therapy, in 2017.
Information technology
In February 2020, China launched a mobile app to deal with the disease outbreak.Users are asked to enter their name and ID number. The app is able to detect 'close contact' using surveillance data and therefore a potential risk of infection. Every user can also check the status of three other users. If a potential risk is detected, the app not only recommends self-quarantine, it also alerts local health officials.Psychological support
Infected individuals may experience distress from quarantine, travel restrictions, side effects of treatment, or fear of the infection itself. To address these concerns, the National Health Commission of China published a national guideline for psychological crisis intervention on 27 January 2020.Prognosis:
Many of those who die of COVID-19 have pre-existing conditions, including hypertension, diabetes mellitus, and cardiovascular disease. In a study of early cases, the median time from exhibiting initial symptoms to death was 14 days, with a full range of 6 to 41 days.In a study by the National Health Commission (NHC) of China, men had a death rate of 2.8% while women had a death rate of 1.7%. In those younger than 50 years, the risk of death is less than 0.5%, while in those older than 70 it is more than 8%. No deaths had occurred in people younger than 10 as of 26 February 2020[update].
Availability of medical resources and the socioeconomics of a region may also affect mortality.
Histopathological examinations of post-mortem lung samples showed diffuse alveolar damage with cellular fibromyxoid exudates in both lungs. Viral cytopathic changes were observed in the pneumocytes. The lung picture resembled acute respiratory distress syndrome (ARDS).
It is unknown if past infection provides effective and long-term immunity in people who recover from the disease. Immunity is likely, based on the behaviour of other coronaviruses,but cases in which recovery from COVID-19 have been followed by positive tests for coronavirus at a later date have been reported. It is unclear if these cases are the result of reinfection, relapse, or testing error.
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