Big global push needed to regulate wet markets and curb wildlife trade

Animal-borne viruses that jump to humans are responsible for the most devastating pandemics in history

The Covid-19 pandemic exposed gaps in the ability of all countries to prevent, detect and respond to an infectious disease outbreak caused by a novel coronavirus. As the Global Health Security Index (2019) declared, no country was prepared to deal with an accidental or deliberate release of a diabolical pathogen.

The most glaring gap in the US was its inability to rapidly detect, trace and isolate cases. China has legitimate questions to answer about its outbreak prevention and risk communication systems.

Between these two great powers lie 193 other countries with their own gaps and challenges. As all countries have barriers to overcome in their health security systems, it is counterproductive to pick on individual countries in a fault-finding competition that will inevitably result in a race to the bottom. Co-operation rather than competition is required to successfully upscale our readiness to deal with risks that many countries share. One of the most compelling is that which prevents animal-borne viruses called zoonoses from jumping to humans.

The most devastating pandemics in history have been attributed to zoonotic illnesses, which arise from pathogens in an animal host being transmitted to humans. The bubonic plague is caused by the bacterium Yersinia pestis, carried by fleas able to infest a wide range of mammals from common rats to household pets such as dogs and cats. The 1918 influenza pandemic was caused by a variant of the H1N1 virus, believed to have originated in birds; and HIV is a relative of the simian immunodeficiency virus (SIV), most likely transmitted to humans through the butchering and consumption of monkey meat.

As Covid-19 continues to spread across the globe, determining the true origin of the virus that caused it is an unsolved puzzle. There is evidence that the novel coronavirus originated in bats and made the jump to humans through a second mammalian host. Many of the earliest identified Covid-19 cases were linked to an open-air seafood market in Wuhan, China.

However, recent analysis of the virus’s genome by geneticist Peter Forster of the University of Cambridge has shown that the location of the first human case of SARS-CoV-2 cannot be definitively attributed to Wuhan. Columbia University’s Ian Lipkin is one of many who are searching for its true origins.

Zoonotic viruses account for more than threequarters of emerging human disease. Of the 1,415 known pathogens of humans, 62% have an animal origin. Many recent epidemics and pandemics, such as the Ebola virus (2014-2016), Middle East respiratory syndrome (Mers, 2012), swine flu (2009), and severe acute respiratory syndrome (SARS, 2002-2004), were caused by the transfer of viruses between wildlife and humans. Over the past several decades there has been an average of almost one new emerging disease a year.

There has also been a notable increase in the frequency of reported zoonotic outbreaks since the beginning of the 21st century. This is due in part to increased surveillance. However, according to a 2005 article published in the journal Emerging Infectious Diseases by Nathan D Wolfe and colleagues at the Johns Hopkins Bloomberg School of Public Health, increased rates of deforestation and bushmeat hunting have also contributed significantly to the emergence of zoonotic diseases.

These are most likely to arise when humans and domesticated animals are exposed to wildlife. Limiting human and livestock exposure to wildlife will therefore be of the utmost importance to help prevent future pandemics. Often referred to as “wet markets”, live animal markets attract a mix of domesticated livestock, wild animals and human customers. This environment provides the optimal conditions for the spread of zoonoses. While these markets provide necessary produce and meats for many communities, the regulation of what is allowed to be sold at the markets has become increasingly important.

WILDLIFE TRADE

A 2007 paper by Bruno B Chomel and other authors published in Emerging Infectious Diseases explains that the wildlife, bushmeat and exotic pet trades play a crucial role in the spread of zoonoses. The wildlife trade has an estimated annual value of R112bn, resulting in the capture and translocation of millions of exotic animals and fish each year.

While the human population is becoming increasingly dependent on livestock, many communities still rely on hunting wild animals as a primary food source. Wildlife and exotic pets are often traded, legally or not, at wet markets. This again highlights the risk that unregulated liveanimal markets pose to global health security.

A 2017 article in Nature magazine analysed the factors and mechanisms that lead to the transfer of infectious diseases from animals to humans. The results were used to determine which regions of the world are most at risk for experiencing an emerging infectious disease event.

It was found that tropical regions are the most likely to generate a zoonotic disease, while densely populated urban environments are more likely to observe the effects of an outbreak.

Another factor that increases the risk of zoonotic infections is the conditions under which livestock are kept. A 2012 report commissioned by the UK’s department for international development concluded that regions with high rates of poverty and hunger, coupled with a density of poor livestock farmers, are at significant risk for experiencing zoonoses.

In “Vital Signs: Health Security in SA” (2020, Brenthurst Foundation), Lizeka Tandwa and Janusz Paweska review the risks SA faces regarding zoonoses of concern. They record a history that includes the importation of Marburg virus in 1975, the Ebola virus in 2008, Rift Valley fever outbreaks in 2008-2011, and an alarming increase in the number of human rabies cases in recent years. Exotic pathogens such as Dengue, Zika, yellow fever, Lassa fever, Ebola, Lujo, Nipah, Hendra, and coronaviruses such as SARS and Mers, pose risks. SARS-CoV-2 came to SA as an import, took hold and spread.

The Global Health Security Index (Nuclear Initiative, Johns Hopkins University and The Economist Intelligence Unit), released in October 2019, awarded SA a score of 58.3 out of 100 for its ability to identify, contain and manage zoonotic diseases. Compared with others in the Brics family of countries, Brazil scored 56.3, Russia 15.3, India 27.8 and China 26.7. Only 30 countries achieved a score of 50 or higher, and 165 countries failed to obtain a basic pass. Finland achieved the highest score of 82.

Metrics are useful as targets, but upscaling the management of zoonotic risks will take a new regulatory regime, strong leadership and budgets to drive changes. A co-operative approach under the global moral authority of the World Health Organisation is the only way to get the job done. Finger-pointing and mutual recrimination will not do the trick.

James, a visiting professor at Columbia University, is editor and a contributing author to “Vital Signs: Health Security in SA” (2020). RubinThompson is a pre-med student and research assistant at Columbia.