GLOBAL HEALTH WORKING GROUP
COVID-19: What in the world is Zoonosis? Jennyfer Ambe and Rahwa Osman Co-Chairs WCAPS Global Health Working Group Key Questions: What is zoonosis? What are the known causes of zoonosis? Keywords: Zoonosis, ground zero, wet-markets, chain of infection, pathogen, infectious agent, reservoirs, biothreat, bio risk, Avian Flu, Severe Acute Respiratory Syndrome (SARS-CoV), CoVID-19, Middle East Respiratory Syndrome (MERS-CoV), Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2) Zoonotic diseases or Zoonosis are diseases that cross between vertebrate animals to humans, according to the World Health Organization definition.1 COVID-19 has been suggested to be zoonotic and potentially spread from bats. The Huanan Seafood Wholesale Market in Wuhan, China may have been ground zero for the COVID-19 disease outbreak that has spread across the globe.2 This market sells meat alongside live animals, a common practice not only across China but also in many low- and middle-income countries where animal products are sold in what is known as, “wet-markets”. Wet markets are where live animals can be chosen and slaughtered for the consumer. An infected animal that may be up for sale in these markets can start what is known as a chain of infection. The chain of infection starts with a pathogen, an infectious agent, which may be in the original host or the reservoir. The original host could be infected and ill while reservoirs are animals that carry and shed the virus while not being ill themselves. Human interaction with reservoirs has been the source of outbreaks in the past. Culling of known reservoirs has been a common practice in other outbreaks such as the Avian Flu in China.3 Zoonotic pathogens need a reservoir in which
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World Health Organization. (2020). Health Topic. Zoonosis. Retrieved from https://www.who.int/topics/zoonoses/en/ 2 Woodward, A., (2020, February 10). Chinese Wet Markets. Business Insider. Retrieved on February 15 from https://www.businessinsider.com/wuhan-coronavirus-chinese-wet-market-photos-2020-1 3 Bloomberg News. (2020, February 2) Retrieved on February 19, 2020 from https://www.msn.com/en-sg/news/world/china-culls-18000-chickens-after-h5n1-bird-flu-cases-in-hunan/ar-BBZABqc
they circulate, replicate and spread to a new host. These markets have been connected to several zoonotic disease outbreaks in recent history. Severe Acute Respiratory Syndrome (SARS-CoV) Severe Acute Respiratory Syndrome, also known as SARS is caused by a coronavirus (SARS-CoV) which was identified in 2003.4 The SARS-CoV outbreak started in 2002, in Guangdong Province, China.5 Evidence suggests it started in a wet market. More than one third of the initial cases were people who either sell animals for food, handle or kill animals or those who prepare and serve food. These markets have live animals, seafood, and different cuts of raw meat. They can be crowded with stalls closely packed together; customers, vendors and animals in close proximity with inadequate sanitation and poor and improper drainage for wastewater. This, coupled with a lack of sterilization procedures after the slaughtering of animals, allows for cross-species spread of these viruses to occur. In the case of SARS-CoV, the probable source has been indicated to be bats.6 A recent report has shown that illegal wildlife trading7 at these wet markets may be the source of the unusual interaction between bats and people in China. Middle East Respiratory Syndrome (MERS-CoV) According to the Center for Disease Control (CDC), Middle East Respiratory Syndrome (MERS) is an illness first identified in a patient with severe, fatal pneumonia in Saudi Arabia during the month of September of 2012. MERS is caused by a coronavirus (MERS-CoV) with symptoms such as severe respiratory illness, shortness of breath and fever. The case fatality is about 3-4 people for every 10 patients.8 The origin of this outbreak virus has been suggested to be bats based on its similarity to bat coronavirus species. Furthermore, dromedary camels have been identified as possible reservoirs or intermediate hosts of MERS-Cov based on the neutralizing antibodies against MERS-CoV found in these camels in multiple countries including Somalia, Sudan and Egypt, all major exporters of camels.
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Severe Acute Respiratory Syndrome (SARS). (2003, May). Epidemiology Working Group and the participants at the Global Meeting on the Epidemiology of SARS, 16-17. 5 World Health Organization. (2003) Global Health Security. Consensus document on the Epidemiology of Severe Acute Respiratory Syndrome (SARS). 6 Wendong, et al (2005, October 28).Bats are natural reservoirs of corona like viruses. Science. Retrieved from https://science.sciencemag.org/content/310/5748/676 7 BBC. (January 30,2020).China coronavirus: Misinformation spreads online about origin and scale. Retrieved from https://www.bbc.com/news/blogs-trending-51271037 8 Center for Disease Control and Prevention, Middle East Respiratory Syndrome. Retrieved on February 19, 2020 from https://www.cdc.gov/coronavirus/mers/index.html
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Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2) The name of the coronavirus disease at the center of the current outbreak in Wuhan evolved from the initial name, 2019-nCov to COVID-19 over a period of six weeks. The pathogen is now named Severe Acute Respiratory Syndrome-related Coronavirus 2 (SARS-CoV-2) due to its similarity to SARS-CoV. After six weeks of waiting for a new name, there was some confusion as the new name for the virus was provided. Due to the similarity in name to SARS-CoV, the new virus name could be confusing to some and therefore, for the most part, it is commonly being referred to by the disease it causes, COVID-19. This new virus emerged in Wuhan province of China in January 2020 and has been shown to be related to bat coronaviruses indicating bats as a possible reservoir. Update on the novel Corona Virus Disease (COVID-19) Data reported by the World Health Organization situation report shows a global figure of 75,204 laboratory confirmed cases with a total of 2,006 deaths in China and 3 deaths outside of China . Please see figure 1 below.9 Zoonosis and Outbreaks Most emerging infectious diseases are caused by zoonotic viruses.10 These zoonotic viruses are transferred between vertebrates and humans. Environmental degradation, de-forestation, communities living in close proximity with animals such as bats (also reservoirs for filoviruses) have triggered outbreaks. It is estimated that viruses from twenty -five viral families cause approximately two hundred and sixty-three viral infections in human beings.11 Filoviruses are mainly found in central, eastern and western Africa and are dangerous pathogens that cause hemorrhagic fevers with high fatality rates. Wet markets may perpetuate situations that involve potential and known biohazards which can lead to bio incidents that can cause chain effects where viruses that are usually in animals have infected people. Coordinated disease surveillance in animals and humans can provide some clues as to the possible sites of zoonotic transfer.
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World Health Organization. Corona Virus Disease 2019 (COVID-19). Situation report -30. Retrieved on 2020, February 20 from https://www.who.int/docs/default-source/coronaviruse/situation-reports/20200219-sitrep-30-covid-19.pdf?sfvrsn=6e 50645_6 10 Ndow, G., Ambe, J., Tomori, O., (2019). Emerging infectious diseases: A historical and scientific review. (2019). Socio-cultural dimensions of emerging infectious diseases in Africa: An indigenous response to deadly epidemics. Tangwa, G., Abayomi, A., Ujewe, S., & Munung, N., ch3, Springer International. ISBN 978-3-030-17473-6 11 Carroll, D., Watson, B., Togami, E., Daszak, P., Mazet, J. A., Chrisman, C. J., . . . Tomori, O. (2018). Building a global atlas of zoonotic viruses. Bulletin of the World Health Organization, 96(4), 292-294. doi:10.2471/BLT.17.205005
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