Wet Markets and the Risk of Transmitting Zoonotic Diseases

The term “wet market” was relatively unknown to many people before the COVID-19. Along with the pandemic came the search for answers, with many pointing towards a wet market in Wuhan, China as being the likely origin. It remains unclear whether the zoonotic disease — meaning a virus that originated in animals before jumping to a human host — first appeared in bats or pangolins at the Huanan Seafood Market, which like many wet markets brings live animals to be slaughtered on-site. Videos of wet markets began appearing everywhere in the media, revealing scenes many found disturbing. Bodies of animals were chopped up or hung from hooks while others looked on from cramped cages, blood spattering the floors and screams of anguish filling the air.

In the wake of the COVID-19 pandemic, China has faced international pressure to shut down wet markets permanently. But the issue, and an appropriate solution, are more complex than they may first appear. Wet markets can be found in many countries around the world, including the United States, and not all of them sell living animals. Wet markets should be distinguished from wildlife markets, from which the biggest zoonotic threats arise. Finally, deadly zoonotic disease pandemics can, and have, spawned from factory farms. The problem is far from being China’s alone.

What is doubtless is that zoonotic diseases can arise due to the rearing and killing of animals for human consumption. Placing the blame on China alone is sinophobic, since it is the global demand for animals and their products that renders the world susceptible to future pandemics – something that could be avoided with the widespread adoption of plant-based diets. 

What is a Wet Market?

Wet markets sell products that are perishable, such as animal products, fruits, and vegetables, as opposed to dry markets that sell non-perishable items including electronics and clothing. Some wet markets sell living animals who are slaughtered upon arrival or upon purchase from customers at the market. Though less uncommon, some wet markets sell wildlife and are connected to the wildlife trade, which is illegal in many countries and for certain endangered species.

These markets are called wet due to the state of the floors. They are generally located in the open air or in large vaulted buildings. Because of a lack of air conditioning, water is constantly sprayed over the produce to keep it cool and fresh. Meat, butcher blocks, and vendor stalls are also sprayed continually to keep areas as clean as possible and to wash away the blood from slaughtered animals. 

Wet markets also use a lot of ice. The bodies of recently slaughtered animals must be kept cool to stave off bacterial or pathogenic growth. If a customer only wants a certain portion of the animal, the vendor will likely continue to process the body and keep it on ice until the next customer comes. This melting ice, along with spillage from seafood tanks, and the blood and entrails spilled during the slaughter process contribute to the soaked floors of these markets. Pieces of bodies that aren’t purchased pile up, attracting insects and bacteria. This combination of melting ice, blood, and body parts creates the wet floors these markets are known for.

Wet Markets Around the World

Wet markets are common all over the world. Much like farmer’s markets, each wet market differs widely in terms of offerings, based on product availability, geographic location, and other factors like cultural and religious cuisines. Wet markets don’t exclusively sell animals and many only sell live animals such as fish. Some wet markets, including the Huanan Seafood Wholesale Market thought to be the site of the original transmission of the novel coronavirus, sell “exotic” or wild-caught animals. It is these so-called wildlife markets that pose the greatest risk of zoonotic transmission. 

Wet markets can be the main source of both food and income for countless people all over the world, and they serve as places of community where customers and vendors develop relationships that last years. If wet markets were shut down today, it would have a catastrophic impact not just on the vendors who would lose needed revenue streams, but on all of the people that rely on the markets to buy the food meant to sustain their families. Not only this, but such a broad-strokes approach may be ineffective against zoonotic disease spread since this threat is most significant at markets that sell wild or exotic animals.

People everywhere deserve to have access to healthy, safe food. Yet in some ways, food systems fail everyone – humans, animals, and the environment. Industrial agriculture, which supplies countries including the United States, is rife with such failings at nearly every level. Wet markets too present difficult questions that need addressing. Beyond the glaring welfare issues regarding animals forced to live in squalor and fear leading up to their imminent slaughter, the lack of sanitary enforcement and extremely messy (for lack of a better word) conditions make the possibility of future zoonotic diseases and global pandemics a very real threat. 

Wet Markets in the United States

Because of the media coverage about the coronavirus pandemic, wet markets have come to be associated primarily with China. But the fact that these markets exist in places like the United States can be a surprise to many, with around 80 reportedly existing in New York alone.

While the idea of watching animals die before one’s eyes may be unappealing to many Americans, there are commonalities between wet markets and the grocery stores common throughout North America. In most wet markets in China, the only live animals sold are fish and seafood. Anyone who’s wandered into the meat department of a grocery store like Safeway will be confronted with tanks filled with nervously schooling fish or lobsters with their claws clamped shut with rubber bands. Fish are butchered on order, whereas lobsters are often taken home while still alive. Conceptually, there is little difference between North American grocery stores and Chinese wet markets. 

In a large part, the difference comes down to perception. The lid goes over the lobster pot, making it unnecessary to witness the death of the lobster. And lobsters do go quietly. But deaths these still are, and lobsters – like all animals – more than likely experience pain and fear. Every single animal product consumed in the United States requires lifetimes of suffering and frequently botched deaths where animals are dismembered alive. The difference between an American slaughterhouse and a live animal wet market is that one is hidden carefully away, as the meat industry responsible for their operations knows too well that public knowledge of their practices would be detrimental to their revenue and profits. 

Wet Markets in Asia

Wet markets have long been a part of traditional life throughout Asia. In Singapore, the term “wet market” originated in order to distinguish more traditional markets selling fresh meat from more modern supermarkets that have air conditioning. Wet markets are common in daily life in Thailand, where meat, produce and cooked food can be found. 

In Hong Kong and China, wet markets can be viewed with nostalgia, harkening back to a time before many homes had refrigerators or air conditioning. To this day, many rural, lower-income residents do not have refrigerators in their homes, meaning they make trips to markets on a daily basis. This also means that food must be as fresh as possible since shelf-life cannot be extended through chilling. This is one of the reasons that freshly-killed meat, also called warm meat, is preferred by many people in China.

Warm meat can feature prominently at wet markets since these places sell meat from animals trucked into slaughterhouses only the day before, or else animals are killed right in front of the customer. Either way, wet markets are central to the perception of meat being as fresh as possible. However, trucking living animals long distances to slaughterhouses and markets, where they are often forced to endure days of pain, fear, and filthy conditions, inadvertently providing more opportunities for diseases to take hold. 

Hygiene Of Wet Markets 

There have long been concerns with hygiene in wet markets. Stressed and frightened animals who may be infected with diseases can urinate, defecate, and excrete other biofluids in essentially the same areas where they are killed and their meat is taken by customers. This is a major factor in disease contamination. Further, fragments of animal bodies, such as gills, fins, and other discarded pieces are sprayed onto floors, which can pile up around the feet of both vendors and customers, providing further opportunities for the transmission of diseases. 

The equipment used in wet markets can also be sub-optimal. The chopping blocks used to kill and process animals can be made out of wood. One study investigated wooden cutting boards in wet markets on Hong Kong Island, finding that most surfaces harbored micronisms associated with infections found in hospitals, as well as the presence of antibiotic-resistant genes. 

Zoonotic transmission in wet markets can also come from animals considered to be pests that thrive in these environments. One study looked at rat populations in the wet markets of Thailand, finding that rats are a potential reservoir of zoonotic transmission of pathogens including Salmonella since they live within intimate contact of humans and their food. 

The Risk of Transmitting Zoonotic Diseases

Wet markets that sell live animals have been linked to the emergence of past pandemics. In Hong Kong, a live poultry market transmitted 18 cases of bird-influenza, killing six people. In 2003, a wet market in Shenzen, China caused a SARS coronavirus outbreak due to selling Himalayan palm civets.

Zoonotic diseases are transmitted due to close contact between animals and human beings. The Center for Disease Control states that over half of all known infectious diseases are zoonotic in origin and that 3 out of every 4 new infectious diseases in people coming from animals. What makes wet markets an ideal breeding ground for zoonotic transmission is the diversity of species that can be brought into close contact with humans, especially wildlife. Under more controlled conditions, such as those on western-style factory farms, animals are fed antibiotics their entire lives, thereby limiting the spread of disease (although antibiotic use in factory farms causes other serious health problems in people, such as antibiotic resistance and diseases arising from environmental pollution).

Another key ingredient to zoonotic transmission is cortisol, which is produced in animals, including humans, who are experiencing fear or anxiety. Unfortunately, wet markets can be extremely stressful environments for animals. After enduring long and often painful journeys to the market, animals can be forced to witness the deaths of their companions. The stress this causes animals is likely quite significant.

Under normal circumstances, when an animal’s immune system is confronted with a pathogen, the body responds by generating inflammation to combat it. However, when cortisol is released into the body, the immune-inflammatory response can be repressed, allowing pathogens to proliferate. Human beings sharing close quarters with diseased animals, or eating their flesh recently after death, can create ideal conditions for zoonotic transmission.

Why Are Wet Markets Linked To The Coronavirus Outbreak?

The Huanan Seafood Wholesale Market, which was temporarily closed during the pandemic, is said to be one of the largest wet markets in Central China, with over 1,000 tenants and more than 50,000 square meters of space. According to a report in the South China Morning Post on January 29, 2020, the market had a section that sold some 120 different wildlife animals across 75 species. According to other reports, the wet market sold live animals including, but not limited to wolf cubs, camels, peacocks, bats, pangolins, pigs, crocodiles, and dogs. It is rather uncommon for wet markets to sell “rare” animals such as these, leading many to classify the Huanan Seafood Wholesale Market as a wildlife market rather than a wet market.

What makes wildlife even more threatening than domesticated animals in terms of zoonotic transmission is that wild animals can carry unknown, or novel, diseases that can make the leap to human beings. According to some theories, the coronavirus was passed onto humans by a bat, or via pangolins, who are the world’s most illegally trafficked animals. 

Wet Markets After Coronavirus Outbreak

Wet markets will continue to be widely patronized around the world after the coronavirus pandemic. However, in recent years, trends have been observed that point towards decreasing popularity of these places, in favor of other retailing options such as grocery stores, supermarkets, or online retailers. Younger generations tend to be driving these trends. 

Many experts agree that ending the wildlife trade is of paramount importance if future pandemics are to be avoided. The international wildlife trade is a multibillion-dollar industry, with one study estimating nearly 9,000 species will be at risk of extinction due to the international trade in animals for pets, food, and medicines.

In response to COVID-19, Beijing temporarily banned all trade in wild animals for food, and the Chinese government continues to explore laws that may stem the trade. The biggest problem, however, lies in the demand. As long as people continue to consume wild or “exotic” animals for food or medicine, the wildlife trade will continue, with some suggesting it may simply go underground if it is made illegal. 

Animal Welfare at Wet Markets

Animal welfare regulations vary country by country. In places where wet markets are most common, such as China, these are still developing. For example, there is no legal requirement to “humanely” slaughter animals by first stunning them and rendering them insensitive to pain. Currently, the welfare of animals in wet markets appears to be essentially nonexistent. Many people report seeing live-plucked birds being sold in markets or turtles being cut out from their shells while still squirming to escape. The impetus for increased welfare standards in China does exist, with one survey finding over 70% of respondents supporting the improvement of rearing conditions for farmed animals. Around 65% agreed to establish laws to improve animal welfare. 

It should be noted that welfare regulations do not necessarily equate to reduced cruelty or suffering for animals. Despite the existence of supposedly stronger legislation in the United States, such as the federal Animal Welfare Act, farmed animals are still largely excluded from protections. The Human Slaughter Act requires that animals be stunned before their throats are slit, however, due to production line speeds, many of these stunnings are botched, resulting in deaths every bit as horrific as any at wet markets. 

Conclusion

Wet markets can be places of profound animal suffering, out of which arise life-threatening diseases like the novel coronavirus. Yet not all wet markets are created equal, with the majority not selling trafficked wildlife, which is the biggest potential source of deadly diseases. 

The global demand for wildlife, including species such as pangolins and bats which could well have been the origin of COVID-19, as well as demand for meat and animal products in general, is what truly drives zoonotic transmission and what must be addressed should the world avoid the next great pandemic.