The Epidemiology, Transmission, and Diagnosis of COVID-19

Authors: By: Neesha C. Siriwardane & Rodney Shackelford, DO, Ph.D. April 15, 2020

Introduction to COVID-19

Coronaviruses are enveloped single-stranded RNA viruses of the Coronaviridae family and order Nidovirales (1). The viruses are named for their “crown” of club-shaped S glycoprotein spikes, which surround the viruses and mediate viral attachment to host cell membranes (1-3). Coronaviruses are found in domestic and wild animals, and four coronaviruses commonly infect the human population, causing upper respiratory tract infections with mild common cold symptoms (1,4). Generally, animal coronaviruses do not spread within human populations, however rarely zoonotic coronaviruses evolve into strains that infect humans, often causing severe or fatal illnesses (4). Recently, three coronaviruses with zoonotic origins have entered the human population; severe acute respiratory syndrome coronavirus-2 (SARS) in 2003, Middle Eastern respiratory syndrome (MERS) in 2012, and most recently, coronavirus disease 2019 (COVID-19), also termed SARS-CoV-2, which the World Health Organization declared a Public Health Emergency of International Concern on January 31st, 2020 (4,5). 

COVID19 Biology, Spread, and Origin

COVID-19 replicates within epithelial cells, where the COVID-19 S glycoprotein attaches to the ACE2 receptor on type 2 pneumocytes and ciliated bronchial epithelial cells of the lungs. Following this, the virus enters the cells and rapidly uses host cell biochemical pathways to replicate viral proteins and RNA, which assemble into viruses that in turn infect other cells (3,5,6). Following these cycles of replication and re-infection, the infected cells show cytopathic changes, followed by various degrees of pulmonary inflammation, changes in cytokine expression, and disease symptoms (5-7). The ACE2 receptor also occurs throughout most of the gastrointestinal tract and a recent analysis of stool samples from COVID-19 patients revealed that up to 50% of those infected with the virus have a COVID-19 enteric infection (8).

COVID-19 was first identified on December 31st, 2020 in Wuhan China, when twenty-seven patients presented with pneumonia of unknown cause. Some of the patients worked in the Hunan seafood market, which sold both live and recently slaughtered wild animals (4,9).  Clusters of cases found in individuals in contact with the patients (family members and healthcare workers) indicated a human-to-human transmission pattern (9,10). Initial efforts to limit the spread of the virus were insufficient and the virus soon spread throughout China. Presently COVID-19 occurs in 175 countries, with 1,309,439 cases worldwide, with 72,638 deaths as of April 6th, 2020 (4). Presently, the most affected countries are the United States, Italy, Spain, and China, with the United States showing a rapid increase in cases, and as of April 6th, 2020 there are 351,890 COVID-19 infected, 10,377 dead, and 18,940 recovered (4).  In the US the first case presented on January 19th, 2020, when an otherwise healthy 35-year-old man presented to an urgent care clinic in Washington State with a four-day history of a persistent dry cough and a two-day history of nausea and vomiting.  The patient had a recent travel history to Wuhan, China. On January 20th, 2020 the patient tested positive for COVID-19.  The patient developed pneumonia and pulmonary infiltrates, and was treated with supplemental oxygen, vancomycin, and remdesivir. By day eight of hospitalization, the patient showed significant improvement (11). 

Sequence analyses of the COVID-19 genome revealed that it has a 96.2% similarity to a bat coronavirus collected in Yunnan province, China. These analyses furthermore showed no evidence that the virus is a laboratory construct (12-14). A recent sequence analysis also found that COVID-19 shows significant variations in its functional sites, and has evolved into two major types (termed L and S). The L type is more prevalent, is likely derived from the S type, and may be more aggressive and spread more easily (14,15). 


While sequence analyses strongly suggest an initial animal-to-human transmission, COVID-19 is now a human-to-human contact spread worldwide pandemic (4,9-11). Three main transmission routes are identified; 1) transmission by respiratory droplets, 2) contract transmission, and 3) aerosol transmission (16). Transmission by droplets occurs when respiratory droplets are expelled by an infected individual by coughing and are inhaled or ingested by individuals in relatively close proximity.  Contact transmission occurs when respiratory droplets or secretions are deposited on a surface and another individual picks up the virus by touching the surface and transfers it to their face (nose, mouth, or eyes), propagating the infection. The exact time that COVID-19 remains infective on contaminated surfaces is unknown, although it may be up to several days (4,16). Aerosol transmission occurs when respiratory droplets from an infected individual mix with air and initiate an infection when inhaled (16). Transmission by respiratory droplets appears to be the most common mechanism for new infections and even normal breathing and speech can transmit the virus (4,16,17). The observation that COVID-19 can cause enteric infections also suggests that it may be spread by oral-fecal transmission; however, this has not been verified (8). A recent study has also demonstrated that about 30% of COIVID-19 patients present with diarrhea, with 20% having diarrhea as their first symptom. These patients are more likely to have COVID-19 positive stool upon testing and a longer, but less severe disease course (18).  Recently possible COVID-19 transmission from mother to newborns (vertical transmission) has been documented. The significance of this in terms of newborn health and possible birth defects is currently unknown (19). 

The basic reproductive number or R0, measures the expected number of cases generated by one infection case within a population where all the individuals can become infected. Any number over 1.0 means that the infection can propagate throughout a susceptible population (4). For COVID-19, this value appears to be between 2.2 and 4.6 (4,20,21). Unpublished studies have stated that the COVID10 R0 value may be as high as 6.6, however, these studies are still in peer review. 

COVID-19 Prevention

There is no vaccine available to prevent COVID-19 infection, and thus prevention presently centers on limiting COVID-19 exposures as much as possible within the general population (22). Recommendations to reduce transmission within community include; 1) hand hygiene with simultaneous avoidance of touching the face, 2) respiratory hygiene, 3) utilizing personal protective equipment (PPE) such as facemasks, 4) disinfecting surfaces and objects that are frequently touched, and 5) limiting social contacts, especially with infected individuals  (4,9,17,22). Hand hygiene includes frequent hand-washing with soap and water for twenty seconds, especially after contact with respiratory secretions produced by activities such as coughing or sneezing. When soap and water are unavailable, hand sanitizer that contains at least 60% alcohol is recommended (4,17,22). PPE such as N95 respirators are routinely used by healthcare workers during droplet precaution protocols when caring for patients with respiratory illnesses. One retrospective study done in Hunan, China demonstrated N95 masks were extremely efficient at preventing COVID-19 transfer from infected patients to healthcare workers (4,22-24). It is also likely that wearing some form of mask protection is useful to prevent COVID19 spread and is now recommended by the CDC (25). 

Although transmission of COVID-19 is primarily through respiratory droplets, well-studied human coronaviruses such as HCoV, SARS, and MERS coronaviruses have been determined to remain infectious on inanimate surfaces at room temperature for up to nine days. They are less likely to persist for this amount of time at a temperature of 30°C or more (26). Therefore, contaminated surfaces can remain a potential source of transmission. The Environmental Protection Agency has produced a database of appropriate agents for COVID-19 disinfection (27). Limiting social contact usually has three levels; 1) isolating infected individuals from the non-infected, 2) isolating individuals who are likely to have been exposed to the disease from those not exposed, and 3) social distancing. The later includes community containment, were all individuals limit their social interactions by avoiding group gatherings, school closures, social distancing, workplace distancing, and staying at home (28,29). In an adapted influenza epidemic simulation model, comparing scenarios with no intervention to social distancing and estimated a reduction of the number of infections by 99.3% (28). In a similar study, social distancing was estimated to be able to reduce COVID-19 infections by 92% (29). Presently, these measured are being applied in many countries throughout the world and have been shown to be at least partially effective if given sufficient time (4,17,30). Such measures proved effective during the 2003 SARS outbreak in Singapore (30). 

Symptoms, Clinical Findings, and Mortality 

On average COVID-19 symptoms appear 5.2 days following exposure and death fourteen days later, with these time periods being shorter in individuals 70-years-old or older (31,32). People of any age can be infected with COVID-19, although infections are uncommon in children and most common between the ages of 30-65 years, with men more affected than women (32,33). The symptoms vary from asymptomatic/paucisymptomatic to respiratory failure requiring mechanical ventilation, septic shock, multiple organ dysfunction, and death (4,9,32,33). The most common symptoms include a dry cough which can become productive as the illness progresses (76%), fever (98%), myalgia/fatigue (44%), dyspnea (55%), and pneumoniae (81%), with less common symptoms being headache, diarrhea (26%), and lymphopenia (44%) (4,32,33). Rare events such as COVID-19 acute hemorrhagic necrotizing encephalopathy have been documented and one paper describes conjunctivitis, including conjunctival hyperemia, chemosis, epiphora, or increased secretions in 30% of COVID-19 patients (34,35). Interestingly, about 30-60% of those infected with COVID-19 also experience a loss of their ability to taste and smell (36). 

The clinical features of COVID-19 include bilateral lung involvement showing patchy shadows or ground-glass opacities identified by chest X-ray or CT scanning (34). Patients can develop atypical pneumoniae with acute lung injury and acute respiratory distress syndrome (33). Additionally, elevations of aspartate aminotransferase and/or alanine aminotransferase (41%), C-reactive protein (86%), serum ferritin (63%), and increased pro-inflammatory cytokines, whose levels correlate positively with the severity of the symptoms (4,31-33,37-39).

About 81% of COVID-19 infections are mild and the patients make complete recoveries (38). Older patients and those with comorbidities such as diabetes, cardiovascular disease, hypertension, and chronic obstructive pulmonary disease have a more difficult clinical course (31-33,37-39). In one study, 72% of patients requiring ICU treatment had some of these concurrent comorbidities (40). According to the WHO 14% of COVID-19 cases are severe and require hospitalization, 5% are very severe and will require ICU care and likely ventilation, and 4% will die (41). Severity will be increased by older age and comorbidities (4,40,41). If effective treatments and vaccines are not found, the pandemic may cause slightly less than one-half billion deaths, or 6% of the world’s population (41). Since many individuals infected with COVID-19 appear to show no symptoms, the actual mortality rate of COIVD-19 is likely much less than 4% (42). An accurate understanding of the typical clinical course and mortality rate of COVID-19 will require time and large scale testing.         

COVID-19 Diagnosis

COVID-19 symptoms are nonspecific and a definitive diagnosis requires laboratory testing, combined with a thorough patient history.  Two common molecular diagnostic methods for COVID-19 are real-time reverse polymerase chain reaction (RT-PCR) and high-throughput whole-genome sequencing.  RT-PCR is used more often as it is cost more effective, less complex, and has a short turnaround time. Blood and respiratory secretions are analyzed, with bronchoalveolar lavage fluid giving the best test results (43). Although the technique has worked on stool samples, as yet stool is less often tested (8,43). RT-PCR involves the isolation and purification of the COVID-19 RNA, followed by using an enzyme called “reverse transcriptase” to copy the viral RNA into DNA. The DNA is amplified through multiple rounds of PCR using viral nucleic acid-specific DNA primer sequences. Allowing in a short time the COVID-19 genome ti be amplified millions of times and then easily analyzed (43). RT-PCR COVID-19 testing is FDA approved and the testing volume in the US is rapidly increasing (44,45). The FDA has also recently approved a COVID-19 diagnostic test that detects anti-COVID-19 IgM and IgG antibodies in patient serum, plasma, or venipuncture whole blood (43). As anti-COVID-19 antibody formation takes time, so a negative result does not completely preclude a COVID-19 infection, especially early infections. Last, as COVID-19 often causes bilateral pulmonary infiltrates, correlating diagnostic testing results with lung chest CT or X-ray results can be helpful (4,31-33,37-39).  

Testing for COVID-19 is based on a high clinical suspicion and current recommendations suggest testing patients with a fever and/or acute respiratory illness. These recommendations are categorized into priority levels, with high priority individuals being hospitalized patients and symptomatic healthcare facility workers. Low priority individuals include those with mild disease, asymptomatic healthcare workers, and symptomatic essential infrastructure workers. The latter group will receive testing as resources become available (41,46,47). 

COVID-19 Possible Treatments

Presently research on possible COVIS-19 infection treatments and vaccines are underway (48). At the writing of this article many different drugs are being examined, however any data supporting the use of any specific drug treating COVID-19 is thin as best. A few drugs that might have promise are:  


Hydroxychloroquine has been used to treat malarial infections for seventy years and in cell cultures it has anti-viral effects against COVID-19 (49). In one small non-randomized clinical trial in France, twenty individuals infected with COVID-19 who received hydroxychloroquine showed a reduced COVID-19 viral load, as measured on nasopharyngeal viral carriage, compared to untreated controls (50). Six individuals who also received azithromycin with hydroxychloroquine had their viral load lessened further (50). In one small study in China, a similar drug (chloroquine) was superior in reducing COVID-19 viral levels in treated individuals compared to untreated control individuals (51).  These results are preliminary, but promising. 


Remdesivir is a drug that showed value in treating patients infected with SARS (52). COVID-19 and SARS show about 80% sequence similarity and since Remdesivir has been used to treat SARS, it might have value in treating COVID-19 (52). These trials are underway (48). Remdesivir was also used to treat the first case of COIVD-19 identified within the US (11). There are many other drugs being examined to treat COVID-19 infections, however, the data on all of them is presently slight to none, and research has only begun. There is an enormous research effort underway, and progress should be rapid (48). 


Our understanding of COVID-19 is changing extremely rapidly and new findings come out daily. Combating COVID-19 effectively will require multiple steps; including slowing the spread of the virus through socially isolating and measures such as hand washing. The development of effective drug treatments and vaccines is already a priority and rapid progress is being made (48). Additionally, many areas of the world, such as South American and sub-Saharan Africa, will be affected by the COVID-19 pandemic and are likely to have their economies and healthcare systems put under extreme stress. Dealing with the healthcare crisis in these countries will be very difficult. Lastly, several recent viral pandemics (SARS, MERS, and COVID-19) have come from areas where wildlife is regularly traded, butchered, and eaten in conditions that favor the spread of dangerous viruses between species, and eventually into human populations. The prevention of new viral pandemics will require improved handling of wild species, better separation of wild animals from domestic animals, and better regulated and lowered trade in wild animals, such as bats, which are known to be a risk for carrying potentially deadly viruses to human populations (53). 


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Contributors BC, CW, and YeW had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. CW and BC decided to publish the paper. BC, CW, YeW, PWH, TJ, and FGH provided input on the trial design. BC, CW, YeW, FGH, and PWH were responsible for acquisition, analysis, and interpretation of data. YeW, FGH, PWH, and GF drafted the manuscript. BC, CW, PWH, FGH, GF, TJ, and XG critically revised the manuscript. YeW contributed to statistical analysis. GF gave valuable suggestions for data analysis. All authors contributed to conducting the trial.



No specific antiviral drug has been proven effective for treatment of patients with severe coronavirus disease 2019 (COVID-19). Remdesivir (GS-5734), a nucleoside analogue prodrug, has inhibitory effects on pathogenic animal and human coronaviruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vitro, and inhibits Middle East respiratory syndrome coronavirus, SARS-CoV-1, and SARS-CoV-2 replication in animal models.


We did a randomised, double-blind, placebo-controlled, multicentre trial at ten hospitals in Hubei, China. Eligible patients were adults (aged ≥18 years) admitted to hospital with laboratory-confirmed SARS-CoV-2 infection, with an interval from symptom onset to enrolment of 12 days or less, oxygen saturation of 94% or less on room air or a ratio of arterial oxygen partial pressure to fractional inspired oxygen of 300 mm Hg or less, and radiologically confirmed pneumonia. Patients were randomly assigned in a 2:1 ratio to intravenous remdesivir (200 mg on day 1 followed by 100 mg on days 2–10 in single daily infusions) or the same volume of placebo infusions for 10 days. Patients were permitted concomitant use of lopinavir–ritonavir, interferons, and corticosteroids. The primary endpoint was time to clinical improvement up to day 28, defined as the time (in days) from randomisation to the point of a decline of two levels on a six-point ordinal scale of clinical status (from 1=discharged to 6=death) or discharged alive from hospital, whichever came first. Primary analysis was done in the intention-to-treat (ITT) population and safety analysis was done in all patients who started their assigned treatment. This trial is registered with ClinicalTrials.govNCT04257656.


Between Feb 6, 2020, and March 12, 2020, 237 patients were enrolled and randomly assigned to a treatment group (158 to remdesivir and 79 to placebo); one patient in the placebo group who withdrew after randomisation was not included in the ITT population. Remdesivir use was not associated with a difference in time to clinical improvement (hazard ratio 1·23 [95% CI 0·87–1·75]). Although not statistically significant, patients receiving remdesivir had a numerically faster time to clinical improvement than those receiving placebo among patients with symptom duration of 10 days or less (hazard ratio 1·52 [0·95–2·43]). Adverse events were reported in 102 (66%) of 155 remdesivir recipients versus 50 (64%) of 78 placebo recipients. Remdesivir was stopped early because of adverse events in 18 (12%) patients versus four (5%) patients who stopped placebo early.


In this study of adult patients admitted to hospital for severe COVID-19, remdesivir was not associated with statistically significant clinical benefits. However, the numerical reduction in time to clinical improvement in those treated earlier requires confirmation in larger studies.

For More Information:

Study: Remdesivir Does Not Reduce COVID Mortality

Authors: By Ralph Ellis

October 19, 2020 — A large study sponsored by the World Health Organization found that remdesivir doesn’t help hospitalized patients with COVID-19 survive and doesn’t even shorten the recovery time of those who do survive.

These findings contradict smaller studies which found remdesivir, an antiviral drug, helped hospitalized coronavirus patients recover faster than patients who received a placebo. Those earlier studies led the FDA to grant emergency use authorization for the drug, which has been given to thousands of COVID patients in the United States, including President Donald Trump.

The WHO-sponsored study was conducted from March 22 to Oct. 4 and involved 11,330 patients from 405 hospitals in 30 countries. Patients were given remdesivir and three other drugs singly or in combination.

“These remdesivir, hydroxychloroquine, lopinavir and interferon regimens appeared to have little or no effect on hospitalized COVID-19, as indicated by overall mortality, initiation of ventilation and duration of hospital stay,” the study concluded.

The data was posted online in the preprint server medRxiv and has not been peer-reviewed or published in a scientific journal.

For More Information:

NIH Clinical Trial Shows Remdesivir Accelerates Recovery from Advanced COVID-19

Authors: NIAID Office of Communications

Hospitalized patients with advanced COVID-19 and lung involvement who received remdesivir recovered faster than similar patients who received placebo, according to a preliminary data analysis from a randomized, controlled trial involving 1063 patients, which began on February 21. The trial (known as the Adaptive COVID-19 Treatment Trial, or ACTT), sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, is the first clinical trial launched in the United States to evaluate an experimental treatment for COVID-19. 

An independent data and safety monitoring board (DSMB) overseeing the trial met on April 27 to review data and shared their interim analysis with the study team. Based upon their review of the data, they noted that remdesivir was better than placebo from the perspective of the primary endpoint, time to recovery, a metric often used in influenza trials. Recovery in this study was defined as being well enough for hospital discharge or returning to normal activity level.   

Preliminary results indicate that patients who received remdesivir had a 31% faster time to recovery than those who received placebo (p<0.001). Specifically, the median time to recovery was 11 days for patients treated with remdesivir compared with 15 days for those who received placebo. Results also suggested a survival benefit, with a mortality rate of 8.0% for the group receiving remdesivir versus 11.6% for the placebo group (p=0.059).

More detailed information about the trial results, including more comprehensive data, will be available in a forthcoming report. As part of the U.S. Food and Drug Administration’s commitment to expediting the development and availability of potential COVID-19 treatments, the agency has been engaged in sustained and ongoing discussions with Gilead Sciences regarding making remdesivir available to patients as quickly as possible, as appropriate. The trial closed to new enrollments on April 19. NIAID will also provide an update on the plans for the ACTT trial moving forward. This trial was an adaptive trial designed to incorporate additional investigative treatments.         

For More Information:

The ‘very, very bad look’ of remdesivir, the first FDA-approved COVID-19 drug

Authors: By Jon CohenKai KupferschmidtOct. 28, 2020 , 7:05 PM

October was a good month for Gilead Sciences, the giant manufacturer of antivirals headquartered in Foster City, California. On 8 October, the company inked an agreement to supply the European Union with its drug remdesivir as a treatment for COVID-19—a deal potentially worth more than $1 billion. Two weeks later, on 22 October, the U.S. Food and Drug Administration (FDA) approved remdesivir for use against the pandemic coronavirus SARS-CoV-2 in the United States—the first drug to receive that status. The EU and U.S. decisions pave the way for Gilead’s drug into two major markets, both with soaring COVID-19 cases.

But both decisions baffled scientists who have closely watched the clinical trials of remdesivir unfold over the past 6 months—and who have many questions about remdesivir’s worth. At best, one large, well-designed study found remdesivir modestly reduced the time to recover from COVID-19 in hospitalized patients with severe illness. A few smaller studies found no impact of treatment on the disease whatsoever. Then, on 15 October—in this month’s decidedly unfavorable news for Gilead—the fourth and largest controlled study delivered what some believed was a coup de grâce: The World Health Organization’s (WHO’s) Solidarity trial showed that remdesivir does not reduce mortality or the time COVID-19 patients take to recover.

Science has learned that both FDA’s decision and the EU deal came about under unusual circumstances that gave the company important advantages. FDA never consulted a group of outside experts that it has at the ready to weigh in on complicated antiviral drug issues. That group, the Antimicrobial Drugs Advisory Committee (AMDAC), mixes infectious disease clinicians with biostatisticians, pharmacists, and a consumer representative to review all available data on experimental treatments and make recommendations to FDA about drug approvals—yet it has not convened once during the pandemic.

For More Information:

Peer-reviewed data shows remdesivir for COVID-19 improves time to recovery

Authors:  Beigel, et al. Remdesivir for the Treatment of COVID-19 – A Preliminary Report. The New England Journal of Medicine. DOI: 10.1056/NEJMoa2007764 (2020).  


The investigational antiviral remdesivir is superior to the standard of care for the treatment of COVID-19, according to a report published today in the New England Journal of Medicine. The preliminary analysis is based on data from the Adaptive COVID-19 Treatment Trial (ACTT), sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. The randomized, controlled trial enrolled hospitalized adults with COVID-19 with evidence of lower respiratory tract involvement (generally moderate to severe disease). Investigators found that remdesivir was most beneficial for hospitalized patients with severe disease who required supplemental oxygen. Findings about benefits in other patient subgroups were less conclusive in this preliminary analysis.

The study began on Feb. 21, 2020 and enrolled 1,063 participants in 10 countries in 58 days. Patients provided informed consent to participate in the trial and were randomly assigned to receive local standard care and a 10-day course of the antiviral remdesivir intravenously, developed by Gilead Sciences, Inc., or local standard care and a placebo. The trial was double-blind, meaning neither investigators nor participants knew who was receiving remdesivir or placebo.

The trial closed to enrollment on April 19, 2020. On April 27, 2020 (while participant follow-up was still ongoing), an independent data and safety monitoring board overseeing the trial reviewed data and shared their preliminary analysis with NIAID. NIAID quickly made the primary results of the study public due to the implications for both patients currently in the study and for public health. The report published today in the New England Journal of Medicine describes the preliminary results of the trial.

For More Information:

Remdesivir for the Treatment of Covid-19 — Final Report

Authors: John H. Beigel, M.D., Kay M. Tomashek, M.D., M.P.H., Lori E. Dodd, Ph.D., Aneesh K. Mehta, M.D., Barry S. Zingman, M.D., Andre C. Kalil, M.D., M.P.H., Elizabeth Hohmann, M.D., Helen Y. Chu, M.D., M.P.H., Annie Luetkemeyer, M.D., Susan Kline, M.D., M.P.H., Diego Lopez de Castilla, M.D., M.P.H., Robert W. Finberg, M.D., et al., for the ACTT-1 Study Group Members*



Although several therapeutic agents have been evaluated for the treatment of coronavirus disease 2019 (Covid-19), no antiviral agents have yet been shown to be efficacious.


We conducted a double-blind, randomized, placebo-controlled trial of intravenous remdesivir in adults who were hospitalized with Covid-19 and had evidence of lower respiratory tract infection. Patients were randomly assigned to receive either remdesivir (200 mg loading dose on day 1, followed by 100 mg daily for up to 9 additional days) or placebo for up to 10 days. The primary outcome was the time to recovery, defined by either discharge from the hospital or hospitalization for infection-control purposes only.


A total of 1062 patients underwent randomization (with 541 assigned to remdesivir and 521 to placebo). Those who received remdesivir had a median recovery time of 10 days (95% confidence interval [CI], 9 to 11), as compared with 15 days (95% CI, 13 to 18) among those who received placebo (rate ratio for recovery, 1.29; 95% CI, 1.12 to 1.49; P<0.001, by a log-rank test). In an analysis that used a proportional-odds model with an eight-category ordinal scale, the patients who received remdesivir were found to be more likely than those who received placebo to have clinical improvement at day 15 (odds ratio, 1.5; 95% CI, 1.2 to 1.9, after adjustment for actual disease severity). The Kaplan–Meier estimates of mortality were 6.7% with remdesivir and 11.9% with placebo by day 15 and 11.4% with remdesivir and 15.2% with placebo by day 29 (hazard ratio, 0.73; 95% CI, 0.52 to 1.03). Serious adverse events were reported in 131 of the 532 patients who received remdesivir (24.6%) and in 163 of the 516 patients who received placebo (31.6%).


Our data show that remdesivir was superior to placebo in shortening the time to recovery in adults who were hospitalized with Covid-19 and had evidence of lower respiratory tract infection. (Funded by the National Institute of Allergy and Infectious Diseases and others; ACTT-1 number, NCT04280705. opens in new tab.)

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Severe covid-19 pneumonia: pathogenesis and clinical management

Authors: Amy H Attaway, assistant professor of medicine, associate director, COPD center1,  Rachel G Scheraga, assistant professor of medicine2,  Adarsh Bhimraj, head, section of neurological infections; staff, infectious diseases1,  Michelle Biehl, associate staff, pulmonary and critical care medicine; director, post ICU recovery clinic1,  Umur Hatipoğlu, associate professor of medicine; director, respiratory therapy; director, COPD center1


Severe covid-19 pneumonia has posed critical challenges for the research and medical communities. Older age, male sex, and comorbidities increase the risk for severe disease. For people hospitalized with covid-19, 15-30% will go on to develop covid-19 associated acute respiratory distress syndrome (CARDS). Autopsy studies of patients who died of severe SARS CoV-2 infection reveal presence of diffuse alveolar damage consistent with ARDS but with a higher thrombus burden in pulmonary capillaries. When used appropriately, high flow nasal cannula (HFNC) may allow CARDS patients to avoid intubation, and does not increase risk for disease transmission. During invasive mechanical ventilation, low tidal volume ventilation and positive end expiratory pressure (PEEP) titration to optimize oxygenation are recommended. Dexamethasone treatment improves mortality for the treatment of severe and critical covid-19, while remdesivir may have modest benefit in time to recovery in patients with severe disease but shows no statistically significant benefit in mortality or other clinical outcomes. Covid-19 survivors, especially patients with ARDS, are at high risk for long term physical and mental impairments, and an interdisciplinary approach is essential for critical illness recovery.


The ongoing outbreak of the coronavirus disease 2019 (covid-19) has posed immense challenges for the research and medical communities. This review focuses on the epidemiologic and clinical features of covid-19, the pathophysiologic mechanisms, inpatient respiratory support, and the evidence to date on drug treatments. It also covers the recovery and long term management of patients with covid-19 pneumonia. The review is aimed at clinicians and intensivists caring for patients with severe covid-19 pneumonia as defined by the National Institutes of Health,1 referring to individuals with SARS-CoV-2 infection confirmed by polymerase chain reaction (PCR) testing who have SpO2 <94% on room air at sea level, a ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) <300 mm Hg, respiratory frequency >30 breaths/min, or lung infiltrates >50%.

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