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COVID-19 – What Have We Learned So Far?

Authors: Katrina Mountfort, Senior Medical Writer, Touch Medical Media, UK Published Online: March 18th 2020

The COVID-19 outbreak is imposing unprecedented challenges for researchers and healthcare providers, with wide variations in mortality rate being reported. As the world prepares for potential further spread, recent publications can provide us with some useful epidemiological insights into the evolving pandemic, and highlight knowledge gaps.

A recent report in the New England Journal of Medicine described the first 425 cases reported in Wuhan, China, the epicentre of the outbreak. The median age of the patients was 59 years, with higher morbidity and mortality among the elderly and among those with coexisting conditions.1 Of interest, there were no cases in children younger than 15 years of age. One recent study has suggested that children are as likely to become infected as adults; presumably their symptoms are so mild that their infection is not readily detected.2 Currently reported fatality rates vary widely but, given that many asymptomatic or minimally symptomatic cases may not have been reported, is likely to be below 1%.3

What is noteworthy about COVID-19, however, is the efficiency of its transmission. Its basic reproduction number (R0) appears to be 2.2, meaning that, each infected person spreads the infection to an additional two people. Until this number falls below 1.0, it is likely that the outbreak will continue to spread.1 Transmission occurs largely among symptomatic individuals, though asymptomatic individuals have transmitted the disease to multiple family members.4 Of particular concern, the viral load is particularly high in the oropharynx early in the course of the infection, facilitating transmission from people with minimal symptoms.5 By contrast, transmission of severe acute respiratory syndrome coronavirus (SARS-CoV) did not readily occur during early stages, and most transmission occurred when infected individuals presented with severe illness, thus making it easier to contain the 2003 outbreak.6

While our understanding of COVID-19 is increasing every day, much remains unknown. While older age and comorbidities, particularly hypertension, diabetes mellitus, coronary heart diseases and cerebrovascular disease, have emerged as key risk factors for severe illness,7 other risk factors have not been elucidated. At present, there are no effective treatment strategies, and the safety of supportive care strategies such as oxygen by high-flow nasal cannula and non-invasive ventilation are not certain.8 There is also a need for research to understand the source of the outbreak by the study of animals and animal handlers in markets.

As the crisis escalates, the safety of healthcare providers is of increasing concern. At the time of writing, it is estimated that 3,000 health care workers in China have been infected and 22 have died.9 Specific training and encouragement of adherence to barrier precautions and hygiene recommendations are essential. In addition, many healthcare workers have comorbidities that increase their risk of severe infection or death if they become infected with COVID-19. Organisations may need to redeploy such workers, including physicians, from the highest risk sites. It is also important to emphasise the importance of self-care for healthcare workers. Providing food, rest breaks and time off will become increasingly important.9

Efforts to hasten the development of vaccine strategies and treatments are accelerating. A number of vaccine candidates are expected to enter phase I clinical trials in early spring.10 In terms of treatment, a number of approaches are being investigated, including the antiviral therapy lopinavir–ritonavir, interferon-1 beta, the RNA polymerase inhibitor remdesivir, and chloroquine.11 Potential therapies that are still in the preclinical phase of development will not be prioritised over more advanced candidates with available clinical safety and efficacy data, as it is essential to identify products that are ready for testing at the earliest opportunity.11 There is a mean interval of 9.1–12.5 days between the onset of illness and hospitalisation,11 which may provide a window of opportunity for intervention to avoid the progression to serious disease.

Telemedicine has a potentially useful role to play in the response to COVID-19, by the use of “forward triage” before patients arrive in the emergency department. Patients can be given a tablet and isolated in a room. Essential information be provided without exposing staff by using commercial systems or paired tablets, allowing communication with a clinician through a dedicated connection. Tablet computers can be cleaned between patients using recommended infection-control procedures. Telemedicine can also provide rapid access to specialists who are not available in person. Healthcare workers who are self-isolating can also cover telemedicine services, freeing up other physicians to perform in-person care. At present, such services are not widely available but this pandemic has highlighted their potential utility.12

While community mitigation efforts to control the spread of COVID-19 are being implemented across the world, we can learn much from the COVID-19 outbreak. At the very least, it serves as a reminder of the need for constant surveillance, prompt diagnosis and robust research to understand new pathogens and our susceptibilities to them.



  1.  Li Q, Guan X, Wu P, et al. Early transmission dynamics in Wuhan, China, of novel coronavirus-infected pneumonia. N Engl J Med. 2020;10.1056/NEJMoa2001316.
  2. Bi Q, Wu, Y, Mei, S, et al. Epidemiology and transmission of COVID-19 in Shenzhen China: Analysis of 391 cases and 1,286 of their close contacts. Preprint; https://doi.org/10.1101/2020.03.03.20028423 Available at www.medrxiv.org/content/10.1101/2020.03.03.20028423v1 (accessed 18 March 2020).
  3. Fauci AS, Lane HC, Redfield RR. Covid-19 – Navigating the uncharted. N Engl J Med. 2020;10.1056/NEJMe2002387.
  4. Bai Y, Yao L, Wei T, et al. Presumed asymptomatic carrier transmission of COVID-19, JAMA. 2020;10.1001/jama.2020.2565.
  5. Zou L, Ruan F, Huang M, et al. SARS-CoV-2 viral load in upper respiratory specimens of infected patients. N Engl J Med. 2020;10.1056/NEJMc2001737.
  6. Peiris JS, Yuen KY, Osterhaus AD, Stöhr K. The severe acute respiratory syndrome. N Engl J Med. 2003;349:2431–41.
  7. Fang L, Karakiulakis G, Roth M. Are patients with hypertension and diabetes mellitus at increased risk for COVID-19 infection? Lancet Respir Med. 2020;10.1016/s2213-2600(20)30116-8.
  8. Murthy S, Gomersall CD, Fowler RA. Care for critically ill patients with COVID-19. JAMA. 2020;10.1001/jama.2020.3633.
  9. Adams JG, Walls RM. Supporting the health care workforce during the COVID-19 global epidemic. JAMA. 2020;10.1001/jama.2020.3972.
  10. WHO. DRAFT landscape of COVID-19 candidate vaccines –18 February 2020. 2020. Available at: www.who.int/blueprint/priority-diseases/key-action/list-of-candidate-vaccines-developed-against-ncov.pdf (accessed 16 March 2020).
  11. WHO. WHO R&D Blueprint – Informal consultation on prioritization of candidate therapeutic agents for use in novel coronavirus 2019 infection. 2020. Available at: https://apps.who.int/iris/bitstream/handle/10665/330680/WHO-HEO-RDBlueprint%28nCoV%29-2020.1-eng.pdf (accessed 16 March 2020).
  12. Hollander JE, Carr BG. Virtually perfect? Telemedicine for Covid-19. N Engl J Med. 2020;10.1056/NEJMp2003539.
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