Review - (2021) Volume 9, Issue 10
Covid-19 (Pandemic): A Review Article
Alisha Ishrath1*, Mohammed Mazher Ahmed2, Namarata Pal3 and Siri Muppidi4
*Correspondence: Alisha Ishrath, Department of Pharmaceutical Biotechnology, Mesco College of Pharmacy, India, Email:
Coronaviruses are a group of enveloped viruses with nonsegmented, single-stranded, and positive-sense RNA genomes. Coronaviruses belong to the “Coronaviridae family”, which causes various diseases, from the common cold to SARS and MERS. In March 2020 the World Health Organization declared the SARS-Cov-2 virus a global pandemic. We performed a review to describe existing literature about Corona Virus Disease 2019 (COVID-19) history, Symptoms, Epidemiology, Clinical features, Clinical manifestations, Diagnosis, Treatment, Prevention.
COVID-19, Symptoms, Epidemiology, Clinical features, Clinical manifestations, Diagnosis, Treatment, Prevention
The human body is exposed to a variety of infectious microorganisms, such as viruses, bacteria, fungi, protozoa, and helminths, which cause tissue damage through different mechanisms. Viruses are unique among these five types of infectious organisms in that they can manipulate the host-cell machinery in a unique way and continuously evolve to survive and prosper in all species .
COVID-19 is the disease caused by a new coronavirus called SARS-CoV-2. WHO first learned of this new virus on 31 December 2019, following a report of a cluster of cases of ‘viral pneumonia’ in Wuhan, People’s Republic of China .
Since December 2019, a novel coronavirus disease had rapidly spread throughout China, leading to a global outbreak, and causing considerable public health concern. World Health Organisation (WHO) announced the outbreak of COVID-19 as a global public health emergency on 30 January 2020. In India, the first case of COVID-19 was reported on January 27, 2020, in Kerala district. Since then, there is a wide variation in the reporting of cases across the country. The case reporting is based on the SARS-CoV-2 antigen testing by Real-Time Reverse Transcription Polymerase Chain Reaction (RT-qPCR) or by Rapid Antigen Test (RAT) .
Coronavirus (CoV) is clustered under the viral family group that causes disease in mammals and birds. A pandemic novel coronavirus was named as ‘‘Corona Virus Disease 2019’’ (2019-nCoV) by World Health Organization (WHO) in Geneva, Switzerland. As its RNA pattern is closer to SARS, the 2019 Coronavirus is renamed as SARSCoV- 2 pandemic. It belongs to the subfamily Orthocoronavirinae inside the family Coronaviridae, order Nidovirales, and the realm Riboviria . A two-dimensional view of Corona beneath a transmission electron microscopy reveals a characteristic look of ‘‘paying homage to a crown’’ around the virions. This lead to naming the virus ‘‘Corona’’, meaning ‘‘crown’’ or ‘‘halo’’ in Latin
This is the deadly third-generation virus in Corona family preceded by severe acute respiratory syndrome (SARS) in 2003, killed almost 10% of total affected patients (8429) across 29 international locations and Middle East Respiratory Syndrome (MERS) in 2012, even more lethal with a mortality rate of 30% of the infected patients .
Coronaviruses are enveloped positive sense RNA viruses ranging from 60 nm to 140 nm in diameter with spike like projections on its surface giving it a crown like appearance under the electron microscope; hence the name coronavirus . Four corona viruses namely HKU1, NL63, 229E and OC43 have been in circulation in humans, and generally cause mild respiratory disease.
There have been two events in the past two decades wherein crossover of animal betacorona viruses to humans has resulted in severe disease. The first such instance was in 2002–2003 when a new coronavirus of the β genera and with origin in bats crossed over to humans via the intermediary host of palm civet cats in the Guangdong province of China. This virus, designated as severe acute respiratory syndrome coronavirus affected 8422 people mostly in China and Hong Kong and caused 916 deaths (mortality rate 11%) before being contained. Almost a decade later in 2012, the Middle East respiratory syndrome coronavirus (MERS-CoV), also of bat origin, emerged in Saudi Arabia with dromedary camels as the intermediate host and affected 2494 people and caused 858 deaths (fatality rate 34%) .
A wide range of symptoms are found in COVID-19 patients, ranging from mild/moderate to severe, rapidly progressive, and fulminant disease. Symptoms of COVID-19 are non-specific and disease presentation can range from asymptomatic to severe pneumonia. Incidence of asymptomatic cases ranges from 1.6% to 51.7% and these people do not present typical clinical symptoms or signs and do not present apparent abnormalities in lung computed tomography. The most common symptoms of COVID-19 are fever, cough, myalgia, or fatigue and atypical symptoms include sputum, headache, haemoptysis, vomiting, and diarrhoea. Some patients may present with sore throat, rhinorrhoea, headache, and confusion a few days before the onset of fever, indicating that fever is a critical symptom, but not the initial manifestation of infection. Furthermore, some patients experience loss of smell (hyposmia) or taste (hypogeusia), which are now being considered early warning signs and indications for self-isolation .
The most common symptoms of COVID-19 are
• Dry cough.
Other symptoms that are less common and may affect some patients include
• Loss of taste or smell.
• Nasal congestion.
• Conjunctivitis (also known as red eyes).
• Sore throat.
• Muscle or joint pain.
• Different types of skin rash.
• Nausea or vomiting.
• Chills or dizziness.
Symptoms of severe COVID-19 disease include:
• Shortness of breath.
• Loss of appetite.
• Persistent pain or pressure in the chest.
• High temperature (above 38 °C).
Other less common symptoms are
• Reduced consciousness (sometimes associated with seizures).
• Sleep disorders.
• More severe and rare neurological complications such as strokes, brain inflammation, delirium and nerve damage.
People of all ages who experience fever and/or cough associated with difficulty breathing or shortness of breath, chest pain or pressure, or loss of speech or movement should seek medical care immediately. If possible, call your health care provider, hotline or health facility first, so you can be directed to the right clinic .
All ages are at risk of getting the illness. This is because the ailment is transmitted through large droplets that result from coughing and sneezing by symptomatic individuals. In some instances, the infection can happen from asymptomatic individuals and before the beginning of symptoms. As of March 2020, the WHO announced that there are about 87,317 cases of COVID- 19 globally as well as confirmed cases of deaths is 2,977. This implies that the disease symptoms are mild as only 3.42 per cent of patients with it have died because of the virus. At the same time, the high number of incidences and deaths have been identified in China. It is that 92 per cent of the total number of occurrences have been reported in Asia, mainly China. Importantly, the confirmed incidences are clinically identified and laboratory-confirmed. Further, outside Asia, the number of cases and deaths differs due to the on-going nature of the disease, population density, degree of testing and reporting, and timing of reducing strategies. The features of COVID-19 are categorized into the host of the virus, transmission mode and incubation period. In the first place, the Chinese horseshoe bat is the natural hosts and the terminal hosts are humans. Also, the transmission is from individual to individual through aerosol droplets. Lastly, the incubation period varies from two to fourteen days. Therefore, COVID-19 cumulative incidence differs depending on the country and incidences have been confirmed in almost all continents .
Since the initial report from China, the disease spread rapidly, and the number of cases increased exponentially. On January 11, the first case was reported outside mainland China in Thailand,7 and within months, the disease spread to all the continents except Antarctica. India reported its first case of COVID-19 on January 30, 2020. This rose to three cases by February 3, 2020. No further cases were reported in February 2020. However, by mid-March, the number of infected cases started to increase, and many cases were reported from all over India. The first COVID-19 related death in India was reported on March 12, 2020. By the second week of April, the disease spread to all states in India except Sikkim. At the time of writing this manuscript, there have been 2,170,265 cases and 135,163 deaths globally and 15,712 cases and 507 deaths in India [8,9].
Zoonotic transmission initially appeared to be a plausible cause as majority of early cases had a history of exposure to wet markets . However, by the end of January 2020, the number of people who developed the disease without exposure to the market or another person with respiratory symptoms increased. The spread of the disease among persons who did not visit Wuhan and among healthcare workers suggested a person-to-person spread of the virus [11,12]. The exact mode of transmission of this virus is unknown. But, as with other respiratory viruses, droplet borne infection, either directly or indirectly, through fomites is probably the predominant mode of transmission. At present, there is no evidence for airborne transmission of the virus.12 13 Although virus particles have been detected in stool samples of both symptomatic and convalescing patients, the risk of feco-oral transmission is unclear .
Period of Infectivity
The duration for which a patient with COVID-19 remains infective is unclear. Viral load in the oropharyngeal secretions is highest during the early symptomatic stage of the disease [13,14]. The patient can continue to shed the virus even after symptom resolution . In a study from China, the median duration of virus shedding was 20 days (interquartile range [IQR] 17.0–24.0) amongst the survivors . A study of viral dynamics in mild and severe cases revealed that mild cases tend to clear the viruses early, while severe cases can have prolonged viral shedding . Data from studies using twin respiratory and fecal sampling have shown viral shedding can persist in stools for more than 4 weeks even when respiratory samples are negative . Xu et al identified male sex, delayed hospitalization after illness, and invasive mechanical ventilation as risk factors for prolonged viral shedding . Transmission during the asymptomatic phase has also been reported. In a study from Singapore, 6.4% of the 157 locally acquired cases of COVID-19 were attributed to transmission during the asymptomatic phase of the disease .
The clinical features of this ailment vary, extending from an asymptomatic state to acute respiratory distress syndrome to septic shock and multi-organ dysfunction. Ideally, this ailment is categorized depending on its severity and this include mild, moderate, severe, and critical. The shared symptoms of individuals with the disease include fever (98.6 per cent), tiredness (69.6 per cent), dry cough, and looseness of the bowels.
Asymptomatic infections have been well documented [19-27]. One review estimated that 33 percent of people with SARS-CoV-2 infection never develop symptoms . This estimate was based on four large population-based, cross-sectional surveys, among which the median proportion of individuals who had no symptoms at the time of a positive test was 46 percent (range 43 to 77 percent), and on 14 longitudinal studies, among which a median of 73 percent of initially asymptomatic individuals remained so on follow-up. However, there is still uncertainty around the proportion of asymptomatic infections, with a wide range reported across studies. Additionally, the definition of "asymptomatic" may vary across studies, depending on which specific symptoms were assessed. The range of findings in studies evaluating asymptomatic infections is reflected in the following examples:
• In a COVID-19 outbreak on a cruise ship where nearly all passengers and staff were screened for severe acute respiratory syndrome coronavirus 2 (SARSCoV- 2), approximately 19 percent of the population on board tested positive; 58 percent of the 712 confirmed COVID-19 cases were asymptomatic at the time of diagnosis [29,30]. In studies of subsets of those asymptomatic individuals, who were hospitalized and monitored, approximately 77 to 89 percent remained asymptomatic over time [30,31].
• In a smaller COVID-19 outbreak within a skilled nursing facility, 27 of the 48 residents (56 percent) who had a positive screening test were asymptomatic at the time of diagnosis, but 24 of them developed symptoms over the next seven days .
• Other studies, particularly those conducted among younger populations, have reported even higher proportions of infections that are asymptomatic [33-37]. As an example, in an outbreak on an aircraft carrier, a quarter of the crew, among whom the mean age was 27 years, tested positive for SARS-CoV-2 . Among the 1271 cases, only 22 percent were symptomatic at the time of testing and 43 percent remained asymptomatic throughout the observation period. High rates of asymptomatic infection have also been reported among pregnant women presenting for delivery [2,34].
Patients with asymptomatic infection may have objective clinical abnormalities [24,38]. As an example, in a study of 24 patients with asymptomatic infection who all underwent chest computed tomography (CT), 50 percent had typical ground-glass opacities or patchy shadowing, and another 20 percent had atypical imaging abnormalities . Five patients developed low-grade fever, with or without other typical symptoms, a few days after diagnosis. In another study of 55 patients with asymptomatic infection identified through contact tracing, 67 percent had CT evidence of pneumonia on admission; only two patients developed hypoxia, and all recovered .
As above, some individuals who are asymptomatic at the time of diagnosis go on to develop symptoms (ie, they were actually presymptomatic). In one study, symptom onset occurred a median of four days (range of three to seven) after the initial positive RT-PCR test .
Severity of Symptomatic Infection
Spectrum of infection severity
The spectrum of symptomatic infection ranges from mild to critical; most infections are not severe [19,39-44]. Specifically, in a report from the Chinese Centre for Disease Control and Prevention that included approximately 44,500 confirmed infections with an estimation of disease severity :
• Mild disease (no or mild pneumonia) was reported in 81 percent.
• Severe disease (eg, with dyspnea, hypoxia, or >50 percent lung involvement on imaging within 24 to 48 hours) was reported in 14 percent.
• Critical disease (eg, with respiratory failure, shock, or multiorgan dysfunction) was reported in 5 percent.
• The overall case fatality rate was 2.3 percent; no deaths were reported among noncritical cases.
Similarly, in a report of 1.3 million cases reported to the United States Centers for Disease Control and Prevention (CDC) through the end of May 2020, 14 percent were hospitalized, 2 percent were admitted to the intensive care unit (ICU), and 5 percent died . The risk of severe illness varied by age and underlying comorbidities.
Infection fatality rates
The case fatality rate only indicates the mortality rate among documented cases. Since many severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are asymptomatic and many mild infections do not get diagnosed, the infection fatality rate (i.e., the estimated mortality rate among all individuals with infection) is considerably lower and has been estimated in some analyses to be between 0.15 and 1 percent, with substantial heterogeneity by location and across risk groups [47-50].
Fatality rates among hospitalized patients
Among hospitalized patients, the risk of critical or fatal disease is high [51-57]. In a study from early in the pandemic that included 2741 patients who were hospitalized for COVID-19 in a New York City health care system, 665 patients (24 percent) died or were discharged to hospice . Of the 647 patients who received invasive mechanical ventilation, 60 percent died, 13 percent were still ventilated, and 16 percent were discharged by the end of the study. The in-hospital fatality rate associated with COVID-19 has been higher than that for influenza [58-60]. As an example, in an analysis of hospital data from the United States Veterans Health Administration, patients with COVID-19 were five times more likely to die during the hospitalization than patients with influenza (21 versus 3.8 percent) .
Over the course of the pandemic, declining in-hospital fatality rates have been reported [61-64]. As an example, in a retrospective study of a national surveillance database in England that included over 21,000 critical care patients with COVID-19, ICU survival improved from 58 percent in late March 2020 to 80 percent by June 2020 . The reasons for this observation are uncertain, but potential explanations include improvements in hospital care of COVID-19 and better allocation of resources when hospitals were not overburdened.
In resource-limited settings, in-hospital mortality rates may be higher than those reported elsewhere. As an example, in a study from 10 countries in Africa, where there was a median of two intensive care specialists in each hospital and a minority of facilities did not have pulse oximetry, the in-hospital 30-day mortality rate following critical care admission was 48 percent . Mortality was associated with underlying comorbidities as well as resource shortages.
Excess deaths during the pandemic
Neither the case fatality rate nor the infection fatality rate account for the full burden of the pandemic, which includes excess mortality from other conditions because of delayed care, overburdened health care systems, and social determinants of health [66-68].
Incubation period and serial interval
The mean or median incubation period of the disease ranges from 5 to 6 days [69,70]. Lauer et al estimated that 2.5% of the patients will develop symptoms within 2.2 days (95% CI, 1.8 to 2.9 days) and 97.5% of patients will develop symptoms within 11.5 days (95% CI, 8.2– 15.6 days).
Serial interval refers to the time interval between the onset of symptoms in the primary case and the secondary case. The mean serial interval is estimated to be approximately 4 to 5 days [71,72]. By analysing data from 468 infector–infectee pairs, Du et al noted that 59 secondary cases had symptoms earlier than their primary case. This suggested that there is a possibility that the transmission of the disease occurred during the asymptomatic phase of illness in this group of patients .
Period of Infectivity
The duration for which a patient with COVID-19 remains infective is unclear. Viral load in the oropharyngeal secretions is highest during the early symptomatic stage of the disease . The patient can continue to shed the virus even after symptom resolution. In a study from China, the median duration of virus shedding was 20 days (interquartile range [IQR] 17.0–24.0) amongst the survivors . A study of viral dynamics in mild and severe cases revealed that mild cases tend to clear the viruses early, while severe cases can have prolonged viral shedding . Data from studies using twin respiratory and fecal sampling have shown viral shedding can persist in stools for more than 4 weeks even when respiratory samples are negative . Transmission during the asymptomatic phase has also been reported. In a study from Singapore, 6.4% of the 157 locally acquired cases of COVID-19 were attributed to transmission during the asymptomatic phase of the disease .
When is a COVID 19 diagnostic test required?
Diagnostic testing for COVID-19 is conducted to find out whether a person is infected with the SARS-CoV-2 virus, responsible forCOVID-19 infection. Your healthcare practitioner may recommend you the same if:
• You are experiencing symptoms of COVID 19 such as high fever, cough, shortness of breath, excessive fatigue, etc.
• You have long-term health conditions such as asthma, heart diseases, etc. and experience a sudden worsening of symptoms.
• You have come in contact with someone tested positive for COVID 19 recently.
• You are a healthcare worker working in a hospital environment.
• You require hospitalization for treatment or surgery of existing medical conditions.
What are the different laboratory tests available to diagnosis COVID 19?
In general, there are two types of tests for diagnosing COVID-19 namely, Antigen or rapid testing and Molecular or PCR testing. The antigen test is often used as a pointof- care test, less expensive and yields quicker results within minutes. However, there is a higher chance of false-negative results as compared to molecular testing. Molecular testing yields more accurate results but are time-consuming .
Initially, early in the pandemic, the understanding of COVID-19 and its therapeutic management was limited, creating an urgency to mitigate this new viral illness with experimental therapies and drug repurposing. Since then, due to the intense efforts of clinical researchers globally, significant progress has been made which has led to a better understanding of not only COVID-19 and its management but also has resulted in the development of novel therapeutics and vaccine development at an unprecedented speed .
Preventive measures are the current strategy to limit the spread of cases. Early screening, diagnosis, isolation, and treatment are necessary to prevent further spread. Preventive strategies are focused on the isolation of patients and careful infection control, including appropriate measures to be adopted during the diagnosis and the provision of clinical care to an infected patient . Important COVID-19 prevention and control measures in community are summarized in Table 1.
|Voluntary quarantine (self-quarantine)||Avoiding crowding|
|Mandatory quarantine||Hand hygiene|
|Hospital||Personal protective equipment|
|Public institution||School measures/closures|
|Others (cruise ships, etc)||Social distancing|
Table 1: COVID-19 prevention and control measures in community.
As everyone across the globe is aware that there is no accurate medicine for Covid-19 till date, hence it is very important to prevent the spread in the society. Notably, COVID-19 is an RNA virus that poses a threat to public health. Currently, the disease has caused thousands of infections and deaths. The main points in preventing the spread in society are hand hygiene, social distancing and quarantine.
- Almutairi MA. The coronavirus disease 2019 (COVID-19) outbreak: Challenges for pediatric dentistry. J Res Med Dent Sci 2021, 9:116-121
- Nagargoje B, Palod A, Dixi J, et al. Seroprevalence of COVID-19 in a city in India: A community-based cross-sectional study. J Res Med Dent Sci 2021; 9:48-53
- Singh DK, Garg A, Bagri S, et al. COVID-19 presentation and effect of associated co-morbidities on severity of illness at a dedicated COVID hospital in North India. J Res Med Dent Sci 2021; 9:49-54.
- Tanu Singhal. A review of coronavirus disease-2019 (COVID-19). Indian J Pediatr 2020; 87:281–286.
- Dane S, Akyuz M. Symptom spectrum and the evaluation of severity and duration of symptoms in patients with COVID-19. J Res Med Dent Sci 2021; 9:262-266.
- Milibari AA. Current situation of coronavirus disease: (COVID-19) Review Article. Health Sci J 2020; 1-4.
- Li Q, Guan X, Wu P. Early transmission dynamics in Wuhan, China, of novel Coronavirus-infected pneumonia. N Engl J Med 2020; 382:1199–1207.
- Chan JF, Yuan S, Kok KH, et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: A study of a family cluster. The lancet 2020; 395:514-23.
- Faridi S, Niazi S, Sadeghi K. A field indoor air measurement of SARS-CoV-2 in the patient rooms of the largest hospital in Iran. Sci Total Environ 2020; 725:138401–138401.
- Chowdhury SD, Oommen AM. Epidemiology of COVID-19. J Dig Endosc 2020; 11:3–7.
- To KKW, Tsang OTY, Leung WS.Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: An observational cohort study. Lancet Infect Dis 2020; S1473-30992030196–1.
- Zhou F, Yu T, Du R. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: A retrospective cohort study Lancet 20203; 95:1054–1062.
- Liu Y, Yan LM, Wan L.Viral dynamics in mild and severe cases of COVID-19. Lancet Infect Dis 2020; S1473-30992030232–2.
- Wu Y, Guo C, Tang L. Prolonged presence of SARS-CoV-2 viral RNA in faecal samples. Lancet Gastroenterol Hepatol 2020; 5:434–435.
- Tong ZD, Tang A, Li KF, et al. Potential presymptomatic transmission of SARS-CoV-2, Zhejiang province, China, 2020. Emerging Infect Dis 2020; 26:1052.
- Chan JF, Yuan S, Kok KH, et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: A study of a family cluster. Lancet 2020; 395:514.
- Liu YC, Liao CH, Chang CF, et al. A locally transmitted case of SARS-CoV-2 Infection in Taiwan. N Engl J Med 2020; 382:1070.
- Chen D, Xu W, Lei Z et al. Recurrence of positive SARS-CoV-2 RNA in COVID-19: A case report. Int J Infect Dis 2020; 93:297-9.
- Mizumoto K, Kagaya K, Zarebski A, et al. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the diamond princess cruise ship, Yokohama, Japan. Euro Surveill 2020; 25.
- Kimball A, Hatfield KM, Arons M, et al. Asymptomatic and presymptomatic SARS-CoV-2 infections in residents of a long-term care skilled nursing facility-King County, Washington. Morb Mortal Wkly Rep 2020; 69:377.
- Wang Y, Liu Y, Liu L, et al. Clinical outcomes in 55 patients with severe acute respiratory syndrome coronavirus 2 who were asymptomatic at hospital admission in Shenzhen, China. J Infect Dis 2020; 221:1770.
- Sutton D, Fuchs K, D'Alton M et al. Universal screening for SARS-CoV-2 in women admitted for delivery. N Engl J Med 2020; 382:2163.
- Gudbjartsson DF, Helgason A, Jonsson H, et al. Spread of SARS-CoV-2 in the icelandic population. N Engl J Med 2020; 382:2302.
- Oran DP, Topol EJ. Prevalence of asymptomatic SARS-CoV-2 infection : A narrative review. Ann Intern Med 2020; 173:362.
- Oran DP, Topol EJ. The proportion of SARS-CoV-2 infections that are asymptomatic: A systematic review. Ann Intern Med 2021; 174:655.
- Sakurai A, Sasaki T, Kato S, et al. Natural history of asymptomatic SARS-CoV-2 infection. N Engl J Med 2020; 383:885.
- Tabata S, Imai K, Kawano S, et al. Clinical characteristics of COVID-19 in 104 people with SARS-CoV-2 infection on the Diamond Princess cruise ship: A retrospective analysis. Lancet Infect Dis 2020; 20:1043.
- Arons MM, Hatfield KM, Reddy SC, et al. Presymptomatic SARS-CoV-2 infections and transmission in a skilled nursing facility. N Engl J Med 2020; 382:2081.
- Baggett TP, Keyes H, Sporn N, et al. Prevalence of SARS-CoV-2 infection in residents of a large homeless shelter in Boston. JAMA 2020; 323:2191.
- Campbell KH, Tornatore JM, Lawrence KE, et al. Prevalence of SARS-CoV-2 among patients admitted for childbirth in southern connecticut. JAMA 2020; 323:2520.
- Louie JK, Scott HM, DuBois A, et al. Lessons from mass-testing for coronavirus disease 2019 in long-term care facilities for the elderly in San Francisco. Clin Infect Dis 2021; 72:2018.
- Kasper MR, Geibe JR, Sears CL, et al. An outbreak of covid-19 on an aircraft carrier. N Engl J Med 2020; 383:2417.
- Letizia AG, Ramos I, Obla A et al. SARS-CoV-2 Transmission among marine recruits during quarantine. N Engl J Med 2020; 383:2407.
- Hu Z, Song C, Xu C, et al. Clinical characteristics of 24 asymptomatic infections with COVID-19 screened among close contacts in Nanjing, China. Sci China Life Sci 2020; 63:706.
- Bajema KL, Oster AM, McGovern OL, et al. Persons evaluated for 2019 novel coronavirus United States, January. MMWR Morb Mortal Wkly Rep 2020; 69:166.
- Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020; 395:497.
- Chen N, Zhou M, Dong X, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: A descriptive study. Lancet 2020; 395:507.
- Wang D, Hu B, Hu C, et al. Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in Wuhan, China. JAMA 2020; 323:1061.
- Liu K, Fang YY, Deng Y, et al. Clinical characteristics of novel coronavirus cases in tertiary hospitals in Hubei province. Chin Med J 2020; 133:1025.
- Yang X, Yu Y, Xu J, et al. Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: A single-centered, retrospective, observational study. Lancet Respir Med 2020; 8:475.
- Wu Z, McGoogan JM. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72 314 cases from the chinese center for disease control and prevention. JAMA 2020; 323:1239.
- Stokes EK, Zambrano LD, Anderson KN, et al. Coronavirus disease 2019 case surveillance-United States. MMWR Morb Mortal Wkly Rep 2020; 69:759.
- Gandhi M, Beyrer C, Goosby E. Masks do more than protect others during COVID-19: Reducing the inoculum of SARS-CoV-2 to protect the wearer. J Gen Intern Med 2020; 35:3063-6.
- World Health Organization. Estimating mortality from COVID-19: Scientific brief. World Health Organization 2020.
- Meyerowitz-Katz G, Merone L. A systematic review and meta-analysis of published research data on COVID-19 infection fatality rates. Int J Infect Dis 2020; 101:138.
- Ioannidis JPA. Reconciling estimates of global spread and infection fatality rates of COVID-19: An overview of systematic evaluations. Eur J Clin Invest 2021; 51:e13554.
- Levin AT, Hanage WP, Owusu-Boaitey N, et al. Assessing the age specificity of infection fatality rates for COVID-19: Systematic review, meta-analysis, and public policy implications. Eur J Epidemiol 2020; 35:1123.
- Richardson S, Hirsch JS, Narasimhan M, et al. Presenting characteristics, comorbidities, and outcomes among 5700 patients hospitalized with COVID-19 in the New York City area. JAMA 2020; 323:2052-2059.
- Myers LC, Parodi SM, Escobar GJ, et al. Characteristics of hospitalized adults with COVID-19 in an integrated health care system in California. JAMA 2020; 32:2195-8.
- Cummings MJ, Baldwin MR, Abrams D, et al. Epidemiology, clinical course, and outcomes of critically ill adults with COVID-19 in New York City: A prospective cohort study. Lancet 2020; 395:1763.
- Petrilli CM, Jones SA, Yang J, et al. Factors associated with hospital admission and critical illness among 5279 people with coronavirus disease 2019 in New York City: Prospective cohort study. Br Med J 2020; 369.
- Lewnard JA, Liu VX, Jackson ML, et al. Incidence, clinical outcomes, and transmission dynamics of severe coronavirus disease 2019 in California and Washington: Prospective cohort study. Br Med J 2020; 369.
- Drake TM, Docherty AB, Harrison EM, et al. Outcome of hospitalization for COVID-19 in patients with interstitial lung disease. An international multicenter study. Am J Respiratory Critical Care Med 2020; 202:1656-65.
- Suleyman G, Fadel RA, Malette KM, et al. Clinical characteristics and morbidity associated with coronavirus disease 2019 in a series of patients in metropolitan Detroit. JAMA Network Open 2020; 3:e2012270.
- Cates J, Lucero-Obusan C, Dahl RM, et al. Risk for in-hospital complications associated with COVID-19 and Influenza-veterans health administration, United States. Morb Morta Week Rep 2020; 69:1528.
- Xie Y, Bowe B, Maddukuri G, et al. Comparative evaluation of clinical manifestations and risk of death in patients admitted to hospital with covid-19 and seasonal influenza: Cohort study. Br Med J 2020; 371.
- Verma AA, Hora T, Jung HY, et al. Characteristics and outcomes of hospital admissions for COVID-19 and influenza in the Toronto area. CMAJ 2021; 193:E410-8.
- Dennis JM, McGovern AP, Vollmer SJ, et al. Improving survival of critical care patients with coronavirus disease 2019 in England: A national cohort study. Crit Care Med 2021; 49:209.
- Horwitz LI, Jones SA, Cerfolio RJ, et al. Trends in COVID-19 risk-adjusted mortality rates. J Hosp Med 2021; 16:90.
- Anesi GL, Jablonski J, Harhay MO, et al. Characteristics, outcomes, and trends of patients with COVID-19 related critical illness at a learning health system in the United States. Ann Intern Med 2021; 174:613.
- Nguyen NT, Chinn J, Nahmias J, et al. Outcomes and mortality among adults hospitalized with COVID-19 at US medical centers. JAMA Network Open 2021; 4:e210417-.
- African COVID-19 critical care outcomes study (ACCCOS) investigators. Patient care and clinical outcomes for patients with COVID-19 infection admitted to African high-care or intensive care units (ACCCOS): A multicentre, prospective, observational cohort study. Lancet 2021; 397:1885.
- Woolf SH, Chapman DA, Sabo RT, et al. Excess deaths from COVID-19 and other causes in the US. JAMA 2021.
- Islam N, Shkolnikov VM, Acosta RJ, et al. Excess deaths associated with covid-19 pandemic in 2020: Age and sex disaggregated time series analysis in 29 high income countries. Br Med J 2021; 373.
- Linton N M, Kobayashi T, Yang Y. Incubation period and other epidemiological characteristics of 2019 novel coronavirus infections with right truncation: A statistical analysis of publicly available case data. J Clin Med 2020; 9:E538–E538.
- Jantien AB, Don K, Wallinga J. Incubation period of 2019 novel coronavirus (2019-nCoV) infections among travellers from Wuhan, China. Eurosurveillance 2020; 25:2000062.
- Nishiura H, Linton N M, Akhmetzhanov AR. Serial interval of novel coronavirus (COVID-19) infections. Int J Infect Dis 2020; 93:284–286.
- Zhang J, Litvinova M, Wang W. Evolving epidemiology and transmission dynamics of coronavirus disease 2019 outside Hubei province, China: A descriptive and modelling study Lancet Infect Dis 2020; S1473-30992030230–9.
- Du Z, Xu X, Wu Y, et al. Serial interval of COVID-19 among publicly reported confirmed cases. Emerg Infect Dis 2020; 26:1341.
- To KK, Tsang OT, Leung WS, et al. Temporal profiles of viral load in posterior oropharyngeal saliva samples and serum antibody responses during infection by SARS-CoV-2: An observational cohort study. Lanc Infect Dis 2020; 20:565-574.
- Zhou F, Yu T, Du R, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: A retrospective cohort study. The Lanc 2020; 395:1054-62.
- Liu Y, Yan LM, Wan L, et al. Viral dynamics in mild and severe cases of COVID-19. Lanc. Infec Dis 2020; 20:656-657.
- Wu Y, Guo C, Tang L. Prolonged presence of SARS-CoV-2 viral RNA in faecal samples. Lancet Gastroenterol Hepatol 2020; 5:434–435.
- Wei WE, Li Z, Chiew C J, et al. Presymptomatic transmission of SARS-CoV-2-Singapore. Morb Mortal Wkly Rep 2020; 69:411–415.
- Cascella M, Rajnik M, Aleem A, et al. Features, evaluation, and treatment of coronavirus (COVID-19). Stat Pearls 2021.
- Güner R, Hasanoğlu I, Aktaş F. COVID-19: Prevention and control measures in community. Turk J Med Sci 2020; 50: 571–577.
Alisha Ishrath1*, Mohammed Mazher Ahmed2, Namarata Pal3 and Siri Muppidi41Department of Pharmaceutical Biotechnology, Mesco College of Pharmacy, Hyderabad, India
2Department of Pharmaceutics, Luqman College of Pharmacy, Gulbarga, Karnataka, India
3Department of Microbiology, Shoolini University, Himachal Pradesh, India
4Department of Pharmacology, Gokuraju Gangaraju College of Pharmacy, Hyderabad, India
Citation: Alisha Ishrath, Mohammed Mazher Ahmed, Namarata Pal, Siri Muppidi, Covid-19 (Pandemic): A Review Article, J Res Med Dent Sci, 2021, 9(10): 281-288.
Received: 26-Sep-2021 Accepted: 12-Oct-2021