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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Prophylaxis against covid-19: living systematic review and network meta-analysis

Authors: Jessica J Bartoszko, methodologist,1 ,*Reed A C Siemieniuk, methodologist, internist,1 ,*Elena Kum, methodologist,1 ,*Anila Qasim, methodologist,1 ,*Dena Zeraatkar, methodologist,1 ,*Long Ge, methodologist,2 ,*Mi Ah Han, methodologist,3Behnam Sadeghirad, assistant professor,1,4Arnav Agarwal, methodologist, internist,1,5Thomas Agoritsas, methodologist, internist,1,6Derek K Chu, methodologist, immunologist,1,7Rachel Couban, librarian,4Andrea J Darzi, methodologist,1Tahira Devji, methodologist,1Maryam Ghadimi, methodologist,1Kimia Honarmand, methodologist, critical care physician,8Ariel Izcovich, methodologist, internist,9Assem Khamis, data analyst,10Francois Lamontagne, methodologist, critical care physician,11Mark Loeb, methodologist, infectious disease physician,1,7Maura Marcucci, methodologist, internist,1,7Shelley L McLeod, methodologist, assistant professor,12,13Sharhzad Motaghi, methodologist,1Srinivas Murthy, clinical associate professor, paediatric critical care, infectious diseases physician,14Reem A Mustafa, methodologist, nephrologist,15John D Neary, methodologist, internist,7Hector Pardo-Hernandez, methodologist,16,17Gabriel Rada, methodologist,18,19Bram Rochwerg, methodologist, critical care physician,1,7Charlotte Switzer, methodologist,1Britta Tendal, methodologist,20Lehana Thabane, professor,1Per O Vandvik, methodologist, internist,21Robin W M Vernooij, methodologist,22,23Andrés Viteri-García, methodologist,18,24Ying Wang, methodologist, pharmacist,1Liang Yao, methodologist,1Zhikang Ye, methodologist, pharmacist,1Gordon H Guyatt, methodologist, internist,1,7 and Romina Brignardello-Petersen, methodologist1

BMJ. 2021; 373: n949.Published online 2021 Apr 26. doi: 10.1136/bmj.n949



To determine and compare the effects of drug prophylaxis on SARS-CoV-2 infection and covid-19.


Living systematic review and network meta-analysis.

Data sources

World Health Organization covid-19 database, a comprehensive multilingual source of global covid-19 literature to 25 March 2021, and six additional Chinese databases to 20 February 2021.

Study selection

Randomized trials of people at risk of covid-19 who were assigned to receive prophylaxis or no prophylaxis (standard care or placebo). Pairs of reviewers independently screened potentially eligible articles.


Random effects Bayesian network meta-analysis was performed after duplicate data abstraction. Included studies were assessed for risk of bias using a modification of the Cochrane risk of bias 2.0 tool, and certainty of evidence was assessed using the grading of recommendations assessment, development, and evaluation (GRADE) approach.


The first iteration of this living network meta-analysis includes nine randomised trials—six of hydroxychloroquine (n=6059 participants), one of ivermectin combined with iota-carrageenan (n=234), and two of ivermectin alone (n=540), all compared with standard care or placebo. Two trials (one of ramipril and one of bromhexine hydrochloride) did not meet the sample size requirements for network meta-analysis. Hydroxychloroquine has trivial to no effect on admission to hospital (risk difference 1 fewer per 1000 participants, 95% credible interval 3 fewer to 4 more; high certainty evidence) or mortality (1 fewer per 1000, 2 fewer to 3 more; high certainty). Hydroxychloroquine probably does not reduce the risk of laboratory confirmed SARS-CoV-2 infection (2 more per 1000, 18 fewer to 28 more; moderate certainty), probably increases adverse effects leading to drug discontinuation (19 more per 1000, 1 fewer to 70 more; moderate certainty), and may have trivial to no effect on suspected, probable, or laboratory confirmed SARS-CoV-2 infection (15 fewer per 1000, 64 fewer to 41 more; low certainty). Owing to serious risk of bias and very serious imprecision, and thus very low certainty of evidence, the effects of ivermectin combined with iota-carrageenan on laboratory confirmed covid-19 (52 fewer per 1000, 58 fewer to 37 fewer), ivermectin alone on laboratory confirmed infection (50 fewer per 1000, 59 fewer to 16 fewer) and suspected, probable, or laboratory confirmed infection (159 fewer per 1000, 165 fewer to 144 fewer) remain very uncertain.


Hydroxychloroquine prophylaxis has trivial to no effect on hospital admission and mortality, probably increases adverse effects, and probably does not reduce the risk of SARS-CoV-2 infection. Because of serious risk of bias and very serious imprecision, it is highly uncertain whether ivermectin combined with iota-carrageenan and ivermectin alone reduce the risk of SARS-CoV-2 infection.

For More Information:

Critics Fault Henry Ford Hydroxychloroquine Study Methodology, Conclusion

Authors: by Alex McLenon | July 15, 2020

One critic says the study, which found the drug led to fewer COVID-19 deaths, did not used a randomized trial and patients not administered the drug were more likely to die anyway.

A recent Henry Ford Health System study finding COVID-19 patients treated with hydroxycloroquine were less likely to die from the virus is drawing skepticism from some medical professionals. 

Critics say the research is an “observational study” that did not make use of random control groups. Steven Nissen, chief academic officer of the Heart & Vascular Institute at the Cleveland Clinic, says the study’s methodology preordained its conclusion. 

“I can tell you it doesn’t prove anything.” — Steven Nissen, Cleveland Clinic

In a randomized study, “you assign people to get one therapy or another and then find out how they do,” Nissen said. This study, however, “was what’s known as an observational study, where you look at people who got the drug compared to people who didn’t.”

Nissen says the Henry Ford patients not given hydroxychloroquine based on risk of side effects were already more likely to die from the virus. The Henry Ford researchers counter that they used different dosing methods than other studies. 

While Henry Ford says its study is peer reviewed, Nissen says that does not mean the findings are credible. 

“What a peer review person might have said is ‘look, it’s worth publishing but it doesn’t prove anything’ and I can tell you it doesn’t prove anything,” Nissen said. ”And there is nobody who’s working in this area who has any knowledge of this that says it’s a reliable study.” 

Nissen says the US Food and Drug Administration has verified hydroxychloroquine does not help treat COVID-19 through studies using random control groups. The FDA recently withdrew permission for the treatment based on more reliable studies that contradict the health system’s findings.

For More Information:

An Update: Is hydroxychloroquine effective for COVID-19?

Authors: Medically reviewed by Last updated on Feb 2, 2021.

Multiple studies provide data that hydroxychloroquine (brand name: Plaquenil) does not provide a medical benefit for hospitalized patients with COVID-19. Hydroxychloroquine, an FDA-approved prescription drug used for malaria, rheumatoid arthritis and lupus erythematosus, has been suggested as a possible treatment or preventive for COVID-19 based on demonstrated antiviral or immune system activity.

In June 2020, the FDA revoked the emergency use authorization (EUA) of oral hydroxychloroquine and chloroquine phosphate for the treatment of COVID-19. An EUA can allow quicker access to critical medical products when there are no approved alternative options.

  • Based on an evaluation of the scientific data to date, the FDA concluded that chloroquine and hydroxychloroquine are not likely to be effective in the treatment of COVID-19 for the authorized uses in the EUA.
  • In addition, the risk for serious side effects with hydroxychloroquine and chloroquine phosphate are a concern. This includes the possibility of adverse cardiovascular (heart) events such as an abnormal heart rhythm which could be fatal.
  • Additional worldwide studies are still ongoing to assess the use of these agents for the treatment or prevention or COVID-19, including early-stage outpatient and use with supplements such as zinc or vitamin D or with azithromycin. However, the FDA states hydroxychloroquine should not be used outside of clinical trials in the U.S.

The World Health Organization (WHO) and the U.S. National Institutes of Health (NIH) have also stopped studies evaluating hydroxychloroquine for the treatment of COVID-19 due to a lack of benefit. Current NIH and US treatment guidelines do not recommend use of hydroxychloroquine and chloroquine phosphate for COVID-19 treatment outside of clinical studies.

Although earlier studies suggested that hydroxychloroquine could inhibit the SARs-CoV-2 virus and was more potent than chloroquine, recent studies do not support the use of hydroxychloroquine or chloroquine phosphate. The FDA stated on June 15, 2020 that the suggested dosing regimens for chloroquine and hydroxychloroquine are unlikely to kill or inhibit the virus that causes COVID-19.

Do studies show hydroxychloroquine is not effective for COVID-19?

Yes, multiple studies provide data that hydroxychloroquine is ineffective in the treatment of SARS-CoV-2, the virus that causes COVID-19 disease.

The RECOVERY Trial from the University of Oxford is a large, randomized, controlled, open-label study evaluating a number of potential treatments for patients hospitalized with COVID-19. The study is being conducted by researchers at the University of Oxford in the UK (the hydroxychloroquine arm is now halted).

  • In the RECOVERY Trial, investigators reported that there was no beneficial effect or reduction of death in hospitalized patients with COVID-19 receiving hydroxychloroquine.
  • In this study, 1561 patients received hydroxychloroquine and were compared to 3155 patients receiving standard care only. No difference was found in the primary endpoint, which was the incidence of death at 28 days (26.8% hydroxychloroquine vs. 25% usual care, 95% CI 0.96-1.23; p=0.18).
  • In addition, hydroxychloroquine treatment was associated with an increased length of stay in the hospital and increased need for invasive mechanical ventilation.
  • Based on this data, investigators stopped enrollment in the RECOVERY hydroxychloroquine arm on June 5th, 2020.

For More Information:

Treatment with Hydroxychloroquine Cut Death Rate Significantly in COVID-19 Patients, Henry Ford Health System Study Shows

Authors: COVID-19 Media Briefing with Dr. Adnan Munkarah

DETROIT – Treatment with hydroxychloroquine cut the death rate significantly in sick patients hospitalized with COVID-19 – and without heart-related side-effects, according to a new study published by Henry Ford Health System.

In a large-scale retrospective analysis of 2,541 patients hospitalized between March 10 and May 2, 2020 across the system’s six hospitals, the study found 13% of those treated with hydroxychloroquine alone died compared to 26.4% not treated with hydroxychloroquine. None of the patients had documented serious heart abnormalities; however, patients were monitored for a heart condition routinely pointed to as a reason to avoid the drug as a treatment for COVID-19.

The study was published today in the International Journal of Infectious Diseases, the peer-reviewed, open-access online publication of the International Society of Infectious Diseases (

Patients treated with hydroxychloroquine at Henry Ford met specific protocol criteria as outlined by the hospital system’s Division of Infectious Diseases. The vast majority received the drug soon after admission; 82% within 24 hours and 91% within 48 hours of admission. All patients in the study were 18 or over with a median age of 64 years; 51% were men and 56% African American.

“The findings have been highly analyzed and peer-reviewed,” said Dr. Marcus Zervos, division head of Infectious Disease for Henry Ford Health System, who co-authored the study with Henry Ford epidemiologist Samia Arshad. “We attribute our findings that differ from other studies to early treatment, and part of a combination of interventions that were done in supportive care of patients, including careful cardiac monitoring. Our dosing also differed from other studies not showing a benefit of the drug. And other studies are either not peer reviewed, have limited numbers of patients, different patient populations or other differences from our patients.”

Zervos said the potential for a surge in the fall or sooner, and infections continuing worldwide, show an urgency to identifying inexpensive and effective therapies and preventions.

“We’re glad to add to the scientific knowledge base on the role and how best to use therapies as we work around the world to provide insight,” he said. “Considered in the context of current studies on the use of hydroxychloroquine for COVID-19, our results suggest that the drug may have an important role to play in reducing COVID-19 mortality.”

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Peer-Reviewed Publications about COVID-19 (Coronavirus) by Yale Authors

Sharing knowledge about COVID-19 (coronavirus) is vital to our efforts as we fight the pandemic. Yale researchers are publishing their discoveries about COVID-19 (coronavirus) in peer-reviewed publications. Check back frequently to access the latest findings.

Peer-Reviewed COVID-19 Publications from Yale

  • A new positive SARS-CoV-2 test months after severe COVID-19 illness: reinfection or intermittent viral shedding?Tuan J, Spichler-Moffarah A, Ogbuagu OA new positive SARS-CoV-2 test months after severe COVID-19 illness: reinfection or intermittent viral shedding? BMJ Case Reports CP 2021;14:e240531.
  • Hydroxychloroquine treatment does not reduce COVID-19 mortality; underdosing to the wrong patients? – Authors’ replyRentsch CT, DeVito NJ, MacKenna B, Morton CE, Bhaskaran K, Brown JP, Schultze A, Hulme WJ, Croker R, Walker AJ, Williamson EJ, Bates C, Bacon S, Mehrkar A, Curtis HJ, Evans D, Wing K, Inglesby P, Mathur R, Drysdale H, Wong AYS, McDonald HI, Cockburn J, Forbes H, Parry J, Hester F, Harper S, Smeeth L, Douglas IJ, Dixon WG, Evans SJW, Tomlinson L, Goldacre B. Hydroxychloroquine treatment does not reduce COVID-19 mortality; underdosing to the wrong patients? – Authors’ reply. Lancet Rheumatology 2021; epub ahead of print. DOI: 10.1016/S2665-9913(21)00030-8
  • Early initiation of prophylactic anticoagulation for prevention of COVID-19 mortality: a nationwide cohort study of hospitalized patients in the United StatesRentsch CT, Beckman JA, Tomlinson L, Gellad WF, Alcorn C, Kidwai-Khan F, Skanderson M, Brittain E, King JT, Ho Y-L, Eden S, Kundu S, Lann MF, Greevy RA, Ho PM, Heidenreich PA, Jacobson DA, Douglas IJ, Tate JP, Evans SJ, Atkins D, Justice AC, Freiberg MS. Early initiation of prophylactic anticoagulation for prevention of COVID-19 mortality: a nationwide cohort study of hospitalized patients in the United States. BMJ 2021; (in press)
  • Factors associated with COVID-19-related death using OpenSAFELY.Williamson EJ, Walker AJ, Bhaskaran K, Bacon S, Bates C, Morton CE, Curtis HJ, Mehrkar A, Evans D, Inglesby P, Cockburn J, McDonald HI, MacKenna B, Tomlinson L, Douglas IJ, Rentsch CT, Mathur R, Wong AYS, Grieve R, Harrison D, Forbes H, Schultze A, Croker R, Parry J, Hester F, Harper S, Perera R, Evans SJW, Smeeth L, Goldacre B. Factors associated with COVID-19-related death using OpenSAFELY. Nature 2020, 584:430-436.
  • Risk of COVID-19-related death among patients with chronic obstructive pulmonary disease or asthma prescribed inhaled corticosteroids: an observational cohort study using the OpenSAFELY platform.Schultze A, Walker AJ, MacKenna B, Morton CE, Bhaskaran K, Brown JP, Rentsch CT, Williamson E, Drysdale H, Croker R, Bacon S, Hulme W, Bates C, Curtis HJ, Mehrkar A, Evans D, Inglesby P, Cockburn J, McDonald HI, Tomlinson L, Mathur R, Wing K, Wong AYS, Forbes H, Parry J, Hester F, Harper S, Evans SJW, Quint J, Smeeth L, Douglas IJ, Goldacre B, OpenSAFELY Collaborative.. Risk of COVID-19-related death among patients with chronic obstructive pulmonary disease or asthma prescribed inhaled corticosteroids: an observational cohort study using the OpenSAFELY platform. Lancet Respir Med 2020, 8:1106-1120.
  • Effect of pre-exposure use of hydroxychloroquine on COVID-19 mortality: a population-based cohort study in patients with rheumatoid arthritis or systemic lupus erythematosus using the OpenSAFELY platform.Rentsch CT, DeVito NJ, MacKenna B, Morton CE, Bhaskaran K, Brown JP, Schultze A, Hulme WJ, Croker R, Walker AJ, Williamson EJ, Bates C, Bacon S, Mehrkar A, Curtis HJ, Evans D, Wing K, Inglesby P, Mathur R, Drysdale H, Wong AYS, McDonald HI, Cockburn J, Forbes H, Parry J, Hester F, Harper S, Smeeth L, Douglas IJ, Dixon WG, Evans SJW, Tomlinson L, Goldacre B. Effect of pre-exposure use of hydroxychloroquine on COVID-19 mortality: a population-based cohort study in patients with rheumatoid arthritis or systemic lupus erythematosus using the Open SAFELY platform. Lancet Rheumatol 2021, 3:e19-e27.

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Hydroxychloroquine for the Prevention of Covid-19 — Searching for Evidence

Authors: Myron S. Cohen, M.D.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (Covid-19), has generated a worldwide pandemic. The interruption of its spread depends on a combination of pharmacologic and nonpharmacologic interventions. Initial SARS-CoV-2 prevention includes social distancing, the use of face masks, environmental hygiene, and hand washing.1 Although the most important pharmacologic interventions to prevent SARS-CoV-2 infection are likely to be vaccines, the repurposing of established drugs for short-term prophylaxis is another, more immediate option.

Some researchers have promoted chloroquine and hydroxychloroquine for the treatment and prevention of illness from a variety of microorganisms, including SARS-CoV.2 Hydroxychloroquine can inhibit replication of SARS-CoV-2 in vitro.3 Some observational studies have suggested benefits of hydroxychloroquine for the treatment of Covid-19, whereas other treatment reports have described mixed results.4

Boulware et al. now report in the Journal the results of a randomized trial testing hydroxychloroquine as postexposure prophylaxis for Covid-19.5 This is described by the investigators as a “pragmatic” trial in which participants were recruited through social media and almost all data were reported by the participants. Adults who described a high-risk or moderate-risk exposure to someone with Covid-19 in their household or an occupational setting were provided hydroxychloroquine or placebo (by mail) within 4 days after the reported exposure, and before symptoms would be expected to develop. The authors enrolled 821 participants; an illness that was considered to be consistent with Covid-19 developed in 107 participants (13.0%) but was confirmed by polymerase-chain-reaction assay in less than 3% of the participants. The incidence of a new illness compatible with Covid-19 did not differ significantly between participants receiving hydroxychloroquine (49 of 414 [11.8%]) and those receiving placebo (58 of 407 [14.3%]). Although participant-reported side effects were significantly more common in those receiving hydroxychloroquine (40.1%) than in those receiving placebo (16.8%), no serious adverse reactions were reported.

This trial has many limitations, acknowledged by the investigators. The trial methods did not allow consistent proof of exposure to SARS-CoV-2 or consistent laboratory confirmation that the symptom complex that was reported represented a SARS-CoV-2 infection. Indeed, the specificity of participant-reported Covid-19 symptoms is low,6 so it is hard to be certain how many participants in the trial actually had Covid-19. Adherence to the interventions could not be monitored, and participants reported less-than-perfect adherence, more notably in the group receiving hydroxychloroquine. In addition, those enrolled in the trial were younger (median age, 40 years) and had fewer coexisting conditions than persons in whom severe Covid-19 is most likely to develop,7 so enrollment of higher-risk participants might have yielded a different result.

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Hydroxychloroquine and azithromycin as a treatment of COVID-19: results of an open-label non-randomized clinical trial

Authors: Philippe Gautret 1Jean-Christophe Lagier 2Philippe Parola 1Van Thuan Hoang 3Line Meddeb 4Morgane Mailhe 4Barbara Doudier 4Johan Courjon 5Valérie Giordanengo 6Vera Esteves Vieira 4Hervé Tissot Dupont 2Stéphane Honoré 7Philippe Colson 2Eric Chabrière 2Bernard La Scola 2Jean-Marc Rolain 2Philippe Brouqui 2Didier Raoult 8


Background: Chloroquine and hydroxychloroquine have been found to be efficient on SARS-CoV-2, and reported to be efficient in Chinese COV-19 patients. We evaluate the effect of hydroxychloroquine on respiratory viral loads.

Patients and methods: French Confirmed COVID-19 patients were included in a single arm protocol from early March to March 16th, to receive 600mg of hydroxychloroquine daily and their viral load in nasopharyngeal swabs was tested daily in a hospital setting. Depending on their clinical presentation, azithromycin was added to the treatment. Untreated patients from another center and cases refusing the protocol were included as negative controls. Presence and absence of virus at Day6-post inclusion was considered the end point.

Results: Six patients were asymptomatic, 22 had upper respiratory tract infection symptoms and eight had lower respiratory tract infection symptoms. Twenty cases were treated in this study and showed a significant reduction of the viral carriage at D6-post inclusion compared to controls, and much lower average carrying duration than reported in the litterature for untreated patients. Azithromycin added to hydroxychloroquine was significantly more efficient for virus elimination.

Conclusion: Despite its small sample size, our survey shows that hydroxychloroquine treatment is significantly associated with viral load reduction/disappearance in COVID-19 patients and its effect is reinforced by azithromycin.

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