1.3 The Global Spread of Coronavirus

• 1.3 The Global Spread of Coronavirus

  
  

  By Harriet Jones

  PhD Student. Faculty of Public Health & Policy, LSHTM

  
  

  In this article we will get to understand what a pandemic is, look briefly at some historical pandemics and then how COVID-19 became a pandemic.

  1. What is a pandemic?

  Before understanding what a pandemic is we need to understand a few other terms about to the spread of a disease.

  • An outbreak refers to a sudden increase in the number of cases of a disease in a localised geographical area.

  • An epidemic is an increase in the number of cases of a disease, above what is expected in a given population, during a specific time period. They tend having a much broader geographic range than an outbreak and usually affect more people.

  • A pandemic is a world-wide epidemic. An epidemic that has spread to several countries or continents, usually affecting a large number of people. 

  
  

  It is important to know that slightly different definitions are used by different organisations and not everybody interprets these definitions in exactly the same way. People may use the terms epidemic and outbreak interchangeably and it is not always agreed on when an epidemic becomes a pandemic [1].

  
  

  Figure 1. Definitions of outbreaks, epidemics, pandemics. Image credit: ARCTEC.

  2. Pandemics of the past 

  The world has had pandemics before. In the 14th century pandemic plague, known as the Black Death, caused over 50 million deaths in Europe. The plague is an infectious disease caused by a bacterium called Yersinia pestis which is transmitted by fleas [2]. There were three influenza (flu) pandemics in the 20th century, the largest was called the Spanish Flu which occurred between 1918- 1919. 

  The Spanish flu was caused by a virus called H1N1 and resulted in between 20-50 million deaths worldwide. More recently, in the 21st century, there was another pandemic flu (‘Swine Flu’) between 2009-2010. Fewer people died in this pandemic, which was thought to have caused between 100,000–400,000 deaths.

  
  

  Figure 2. Respiratory virus pandemics of the 20^th and 21^st century. Image credit: ARCTEC

  
  

  3. How did COVID-19 become a pandemic?

  
  

  3.1 First cases identified in China

  In December 2019 there was a cluster of pneumonia cases in Wuhan City, Hubei Province, China. A cluster here means a group of cases in the same place over a short time period. Pneumonia is an infection of the lungs, which can be caused by pathogens such as viruses, bacteria, or fungi [4].
  
  This rise in the number of cases of the disease, above what was expected, was investigated. On the 7th January scientists identified that the pneumonia cases were caused by a new type of coronavirus (later named SARS-CoV-2). The first cases were thought to have originated from a wet market (live market) in Wuhan, called the Huanan Seafood Wholesale Market, where live animals and sea food are traded.
  
  

  3.2 COVID-19 spreads outside China

  On the 13th January 2020 a case of COVID-19 was identified in Thailand. This was the first case seen outside China. There were then cases reported in Japan and the Republic of Korea. On the 20th January cases were reported in the USA and on the 24th January in France. The first case was identified in the UK at the end of January 2020. On the 28th February the first case of COVID-19 in sub-Saharan Africa was reported in Nigeria. 

  
  

  3.3 COVID-19 is declared a pandemic

  By the 11th March 2020 the Director General of the World Health Organisation (WHO) announced that there were more than 118,000 reported cases of COVID-19 spread across 114 countries, and that 4,291 people had died. Because the disease was spreading so quickly, it was severe and not all countries were taking action, the WHO declared that COVID-19 was a pandemic. This is first time in history that there has been a coronavirus pandemic [5].

  
  

  4. The continued spread of COVID-19

  Since the WHO declared COVID-19 a pandemic, the virus has spread to many more countries and many more people have become infected. Italy and Iran were among the first countries to suffer a high number of cases, and a large numbers of deaths were reported from these countries in late February/ early March. By mid-March, the disease had spread to several European countries, and case numbers in the USA had begun to increase. Figure 3 shows how the disease spread to different parts of the world.

   

  Figure 3. Daily COVID-19 case numbers Source: our world in data

  
  

  • You can look at this web-page to see the latest numbers of cases worldwide:  https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports
  • And here to see the latest information on cases in the UK: https://coronavirus.data.gov.uk/?_ga=2.53330216.1442726734.1587568521-55967898.1587568521

  You can see that some countries have had a lot more cases than others. We will explain more about this in section 3.6 "Comparing responses in the UK and other countries".

  
  

  Glossary 

  Bacterium: a single-celled microorganism, which may cause disease in humans. Plural is  bacteria. 

  Epidemic: an increase in disease cases, when a disease spreads to a large number of people in a short period of time.  

  Immune response: the reaction of the immune system to a pathogen.  Generally involves the activation of white blood cells. 

  Outbreak: an above average spike of disease cases within a localised area. 

  Pandemic: an epidemic that has spread worldwide affecting many countries. 

  Pneumonia: A lung infection, which can be caused by bacteria, viruses, or fungi. 

  Virus: an ultramicroscopic infectious non-cellular organism that can replicate inside the cells of living hosts, often with negative consequences.  

  
  

  Further Reading 

  A selection of scientific articles discussing pandemics past and present: 

  1. Wilder-Smith, A. and Freedman, D., 2020. Isolation, quarantine, social distancing and community containment: pivotal role for old-style public health measures in the novel coronavirus (2019-nCoV) outbreak. Journal of Travel Medicine, [online] 27(2).  https://academic.oup.com/jtm/article/27/2/taaa020/5735321 

  2. Fong, M. W., Gao, H., Wong, J. Y., Xiao, J., Shiu, E., Ryu, S....Cowling, B. J. (2020). Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Social Distancing Measures. Emerging Infectious Diseases, 26(5), 976-984. https://dx.doi.org/10.3201/eid2605.190995.  https://wwwnc.cdc.gov/eid/article/26/5/19-0995_article?fbclid=IwAR3BBqcfLSBI79CbItkkeRuwD5oeDmZvs7muoiMn6kAx8ojjIe6XAEbOKvE 

  3. Bedford J, Enria D, Giesecke J, Heymann D, Ihekweazu C, Kobinger G et al. COVID-19: towards controlling of a pandemic. The Lancet [Internet]. 2020; 395(10229):1015-1018. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30673-5/fulltext  

  4.  Lau L, Samari G, Moresky R, Casey S, Kachur S, Roberts L et al. COVID-19 in humanitarian settings and lessons learned from past epidemics. Nature Medicine. 2020;. Available from: https://www.nature.com/articles/s41591-020-0851-2

  5. Rhodes T, Lancaster K, Rosengarten M. A model society: maths, models and expertise in viral outbreaks. Critical Public Health [Internet]. 2020 :1-4. Available from: https://www.tandfonline.com/doi/full/10.1080/09581596.2020.1748310  

  And a further learning course from the CDC on Epidemiology

  6. Centres for Disease Control and Prevention: https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section11.html

  References

  1.  Kelly. H. ‘The Classical definition of a pandemic is not elusive’.  Bulletin of the World Health Organisation. 2011; 89:540-541. Doi: 10. 2471/BLT.11.088815 [Internet] 2020 [Cited 13 May 2020].Available from: https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---11-march-2020 

  2. World Health Organisation. ‘Plague’ [Internet] 2020 [Cited 13 May 2020].Available from: https://www.who.int/health-topics/plague#tab=tab_1 

  3.  Seale. A and Ibeto. M. London school of Hygiene and Tropical medicine ‘Covid-19 Tackling the Novel Coronavirus‘. [Online Course content] 2020 [cited 13 May 2020]. Available from: https://www.futurelearn.com/courses/covid19-novel-coronavirus  

  4. NHS ‘Overview-Pnemonia’ [Internet] 2020 [Cited 12 May 2020]. Available from: https://www.nhs.uk/conditions/pneumonia/ 

  5. World Health Organisation ‘WHO Director-General's opening remarks at the media briefing on COVID-19’. [Internet] 11 March 2020 [Cited 13 May 2020] Available from: https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19---11-march-2020

  6. World Health Organisation" The World Health Organisation explains the timeline of their response to the pandemic,  2020 [Video] accessed on 20 May 2020 via:  https://youtu.be/qHksVwOrpbE

   
  Image Acknowledgements

  Figures 1 & 2, Image credit: ARCTEC.

  Figure 3. ‘Numbers of confirmed Covid-19 cases’, Our World in data. 2020 [Website] accessed 20-May-2020, updated with all current data. Available via: https://ourworldindata.org/covid-cases?country=GBR+CHN+KOR+TWN+ITA+ESP+FRA+SWE+NZL+ZAF