Martin Sanchez
Martin Sanchez

EXPERT REACTION: The first COVID-19 case was likely earlier than records show

Embargoed until: Publicly released:
Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Simulation/modelling: This type of study uses a computer simulation or mathematical model to predict an outcome. The original values put into the model may have come from real-world measurements (eg: past spread of a disease used to model its future spread).

November 17, 2019 is the most likely date of the world's first case of COVID-19, according to international modelling. Researchers adopted modelling previously used to map species heading towards extinction to estimate the earliest cases of COVID-19 in China and some of the first countries the virus spread to. The modelling showed the virus likely emerged in China in early October to mid-November 2019, with November 17 the most likely date. It then spread to Japan on January 3, 2020, before reaching Europe and North America in mid-January.

Journal/conference: PLOS Pathogens

Link to research (DOI): 10.1371/journal. ppat.1009620

Organisation/s: University of Kent, UK

Funder: I.J. was funded by The J.E. PurkynÄ› Fellowship of the Czech Academy of Sciences. DLR and JSR received no specific funding for this work. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Media release

From: PLOS

When did the first COVID-19 case arise?

Novel analysis suggests much earlier, more rapid spread than confirmed cases imply

Using methods from conservation science, a new analysis suggests that the first case of COVID-19 arose between early October and mid-November, 2019 in China, with the most likely date of origin being November 17. David Roberts of the University of Kent, U.K., and colleagues present these findings in the open-access journal PLOS Pathogens.

The origins of the ongoing COVID-19 pandemic remain unclear. The first officially identified case occurred in early December 2019. However, mounting evidence suggests that the original case may have emerged even earlier.

To help clarify the timing of the onset of the pandemic, Roberts and colleagues repurposed a mathematical model originally developed by conservation scientists to determine the date of extinction of a species, based on recorded sightings of the species. For this analysis, they reversed the method to determine the date when COVID-19 most likely originated, according to when some of the earliest known cases occurred in 203 countries.

The analysis suggests that the first case occurred in China between early October and mid-November of 2019. The first case most likely arose on November 17, and the disease spread globally by January 2020. These findings support growing evidence that the pandemic arose sooner and grew more rapidly than officially accepted.

The analysis also identified when COVID-19 is likely to have spread to the first five countries outside of China, as well as other continents. For instance, it estimates that the first case outside of China occurred in Japan on January 3, 2020, the first case in Europe occurred in Spain on January 12, 2020, and the first case in North America occurred in the United States on January 16, 2020.

The researchers note that their novel method could be applied to better understand the spread of other infectious diseases in the future. Meanwhile, better knowledge of the origins of COVID-19 could improve understanding of its continued spread.

Roberts adds, "The method we used was originally developed by me and a colleague to date extinctions, however, here we use it to date the origination and spread of COVID-19. This novel application within the field of epidemiology offers a new opportunity to understand the emergence and spread of diseases as it only requires a small amount of data."

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr Stuart Turville is an Associate Professor in the Immunovirology and Pathogenesis Program at UNSW Sydney's Kirby Institute

The first paper in Lancet from the team in China [listed as reference 1 in this paper] dates the transfer from an animal reservoir to early December. This study then models based on existing data, and states it was two weeks prior (November the 17th). 
 
What would be front-page news would be a study that had serum from people in that area that was reactive to SARS-CoV-2 and these samples were well before October. 

Unfortunately with the current pressure of the lab leak hypothesis and the sensitivities in doing this follow up research in China, it may be some time till we see reports like that. The WHO investigations moving forward may shed more light on the actual dates. What will be key is serum sampling and testing in and around that area and actual definitive results from those types of studies. 
 
Modelling like this is important but always relies on the last known tangible evidence.

Last updated: 24 Jun 2021 11:06am
Declared conflicts of interest:
None declared.
Dr Abrar Chughtai is a Senior Lecturer and the Director of the Master of Infectious Diseases Intelligence Program at the School of Population Health, University of New South Wales Australia

This is an interesting finding but not surprising, as some other indirect evidence also points towards an early origin of SARS-CoV-2. For example, the first case of COVID-19 was reported in the US on 19th January 2020, while the analyses of blood donation samples from American Red Cross showed that the virus was present in the US as early as December 2019. However, cross-reactivity with other human common coronavirus and false-positivity are some limitations of serological studies.
 
Similarly, modelling studies have limitations and results are highly dependent on selection of parameters and data quality. We need to conduct more epidemiological, environmental, genetic and modelling studies to confirm these findings. This may also help in finding the origin of SARS-CoV-2.

Last updated: 24 Jun 2021 11:05am
Declared conflicts of interest:
None declared.
Professor Peter Collignon is an Infectious Diseases Physician and Professor at the Australian National University.

I have already expressed the view with some evidence that it was around much early than others have postulated. I suspect it was in Wuhan even before Nov 2019. The virus has now spread widely around the world and did so within a few months of being first reported in China.

However, it was likely circulating in people in Wuhan for some time before then, as already in December 2019 there were over a dozen strains of the virus. While COVID-19 was not identified to be in high numbers of people in North America and in Europe until February/March 2020, it was likely present a couple of months earlier and during their winters, when spread occurs more readily.

In France, a man who was ill in late December 2019 was retrospectively identified to have had a severe COVID-19 illness. This implies, given the average incubation period for COVID-19 and additionally the time usually taken to develop severe symptoms leading to hospital admission, that the virus was present in Paris since at least mid-December 2019.4 In the USA, it was also likely already present in December 2019. 

Last updated: 24 Jun 2021 11:04am
Declared conflicts of interest:
None declared.

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