By Ruth Hadfield, PhD

Scientific advances in the understanding of COVID-19

Since coronavirus disease-2019 (COVID-19 or 2019-nCoV)/severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first identified in Wuhan, China, in December 2019 over 900 academic research articles have been published. For clinicians already working at the frontline it is a daunting task to keep track of the latest findings as the situation is changing at a rapid pace. This summary aims to condense the newly published research for busy clinicians and provide links to key publications.

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Summary of important newly published articles for 17 March 2020

Long shifts for healthcare workers an important risk factor for COVID-19 infection in Wuhan, China

Journal: Clin Infect Dis

Date published: 17 March 2020

Study population: Case series of 72 healthcare workers at a 3300-bed grade-A tertiary hospital.

Key findings: In total 28 (39%) healthcare workers were diagnosed with COVID-19.  Those working in a high risk setting were almost twice as likely to become infected with COVID-19 compared to those working in a general setting (crude RR =2.13, 95%CI: 1.45-3.95, P<0.05). Other risk factor were length of shifts in a high risk setting, with all workers completing 15 hour+ shifts becoming infected. Poor hand hygiene was also a risk factor.(1)

Link to full text article

Platelet to lymphocyte (PLR) ratio may offer clues to prognosis and length of hospitalisation in COVID-19 patients

Journal: Journal of Medical Virology

Date published: 17 March 2020

Study population: Case series of 30 hospitalised patients with COVID-19 at Huizhou Municipal Central Hospital

Key findings: Patients with elevated platelets were hospitalised for longer; platelet to lymphocyte ratio (PLR), which may be an indicator of cytokine storm, may be a useful new indicator for monitoring in patients with COVID-19.

In patients with severe disease mean PLR was 626, significantly higher than for non-severe patients, who had a mean PLR of 262.

“The advantage of PLR selection is that it reflects both aggregation and inflammatory pathways, and may be more valuable in predicting various inflammations than platelet or lymphocyte counts alone,” the authors commented.(2)

Link to full text article

Infographic of patient demographics and geographic distribution in Italy

Journal: JAMA

Date published: 17 March 2020

Key findings: In Italy data to date show that 40% of cases are female and 60% male, many patients have had mild disease (46%), few symptoms (10.6%) or no symptoms (6.7%). In total 5% of patients were in a critical condition and 25% had severe disease. The case fatality rate is significantly higher in older age groups with a rate of 3.5% in those 60-69 years, 12.5% in 70-79 year olds, 19.7% in 80-89 year olds and 22.7% in ≥90 year olds.(3)

Link to infographic here

Epidemiology & clinical characteristics of 91 hospitalised patients in China

Journal: QJM

Date published: 17 March 2020

Study population: Retrospective case series of 91 cases of confirmed COVID-19 admitted to five hospitals in Zhejiang province, China

Key findings: Symptoms were fever (71%), cough (60%) and fatigue (44%), median incubation period was 6 (IQR, 3-8) days 67% cases had bilateral pneumonia. It was confirmed that 12% of patients had caught the virus on a flight.(4)

Link to full text article

Characteristics of 55 asymptomatic COVID-19 positive hospitalised patients in China

Journal: J Infect Dis

Date published: 17 March 2020

Study population: Retrospective medical record review of 55 asymptomatic COVID-19 positive cases hospitalised in Shenzhen City, China

Key findings:  In this study all asymptomatic patients were tested and then hospitalised as they had a close relative with COVID-19.  Of the 55 asymptomatic individuals who tested positive all went on to develop some symptoms: 14 developed mild disease, 39 developed ‘typical’ COVID-19 and two developed severe COVID-19.(5)

Link to full text article

Impact of corticosteroid treatment in patients with coronavirus disease 2019

Journal: Medical Journal of Australia

Date published: 9 March 2020

Study population:  Observational study of 31 hospitalised patients with mild SARS-CoV-2 disease in Wuhu, Anhui province, China. Most patients studied did not have significant comorbidities.

Intervention: 11 of 31 patients received corticosteroids.

Key findings:

  • There was no statistically significant association between virus clearance time or duration of symptoms in patients who received corticosteroids compared to those who did not.
  • Two patients with Hepatitis B showed delayed viral clearance.


It is interesting to note from this case series of younger patients (mean age 39 years, range 32-54 years) with mild disease that the symptoms on hospitalisation (at an average of 4 days after onset) were:

  • Fever 81% (with average highest temperature of 38 ℃)
  • Cough 61%
  • Myalgia or fatigue 58%
  • Headache 13%
  • Diarrhea 16%
  • Dyspnea (breathlessness) 13%

Link to full text article

No evidence for maternal-fetal transmission in 38 patients

Journal: Arch Pathol Lab Med

Date published: 17 March 2020

Study population: 38 pregnant women with COVID-19 and their newborn infants

Key findings: No intrauterine transmission of SARS-CoV-2 was observed between mother and fetus. Neonatal specimens tested,  including placentas, were negative for the virus.

“At this point in the global pandemic of COVID-19 infection there is no evidence that SARS-CoV-2 undergoes intrauterine or transplacental transmission.”(6)

Link to full text article

No evidence for perinatal transmission from mother to newborn

Journal: Clin Infect Dis

Date published: 17 March 2020

Study population: Perinatal outcomes for two women with COVID-19 during pregnancy

Key findings: “Both mothers and newborns were with excellent outcomes. This will provide evidence of low risk of intrauterine infection by vertical transmission of SARS-CoV-2.”(7)

Link to full text article


1.            Ran L, Chen X, Wang Y, Wu W, Zhang L, Tan X. Risk Factors of Healthcare Workers with Corona Virus Disease 2019: A Retrospective Cohort Study in a Designated Hospital of Wuhan in China. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2020.

2.            Qu R, Ling Y, Zhang YH, Wei LY, Chen X, Li X, et al. Platelet-to-lymphocyte ratio is associated with prognosis in patients with Corona Virus Disease-19. Journal of medical virology. 2020.

3.            Livingston E, Bucher K. Coronavirus Disease 2019 (COVID-19) in Italy. Jama. 2020.

4.            Qian GQ, Yang NB, Ding F, Ma AHY, Wang ZY, Shen YF, et al. Epidemiologic and Clinical Characteristics of 91 Hospitalized Patients with COVID-19 in Zhejiang, China: A retrospective, multi-centre case series. QJM : monthly journal of the Association of Physicians. 2020.

5.            Wang Y, Liu Y, Liu L, Wang X, Luo N, Ling L. Clinical outcome of 55 asymptomatic cases at the time of hospital admission infected with SARS-Coronavirus-2 in Shenzhen, China. The Journal of infectious diseases. 2020.

6.            Schwartz DA. An Analysis of 38 Pregnant Women with COVID-19, Their Newborn Infants, and Maternal-Fetal Transmission of SARS-CoV-2: Maternal Coronavirus Infections and Pregnancy Outcomes. Archives of pathology & laboratory medicine. 2020.

7.            Fan C, Lei D, Fang C, Li C, Wang M, Liu Y, et al. Perinatal Transmission of COVID-19 Associated SARS-CoV-2: Should We Worry? Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2020.


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About the author

Ruth Hadfield is a medical writer with a PhD in clinical medicine and epidemiology from the University of Oxford, UK.