Wet Market Crackdown

Monday, May 11, 2020

Wet markets have been in the headlines since the start of the COVID-19 outbreak. Many initial cases were traced back to a wet market in Wuhan, China, and there have been bipartisan appeals by US senators asking China to shut down all wet markets.

But on May 8, the World Health Organization argued that further investigation is needed into the role of Wuhan wet markets in the COVID-19 pandemic, and recommended that wet markets not be strictly outlawed. In the meantime, they supported enforcement of stricter hygiene and safety standards.

So would shutting down wet markets really address the problem?

Many slaughterhouses in the U.S. are also sources of problematic hygiene and animal conditions that have contributed to the spread of pandemic disease. In the big picture, wet markets may not be the biggest risk for transmission, but simply the easiest to blame.

There has been tremendous pressure to shut down the wet markets, and even Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, has said that wet markets should be shut down as soon as possible.

Jan Vertefeuille of the World Wildlife Fund described wet markets as the “perfect recipe for an epidemic.”

But in the past weeks, there have been doubts over whether the Wuhan wet market and its live animal trade were in fact the place where transmission occurred from animals to humans in the case of COVID-19.

These reports suggest that this initial human infection may have occurred earlier, and that Wuhan market was simply another crowded place where infected people interacted and passed on the disease.

So what is a wet market, and why should we be moving to shut them down?

The term seems to cause a lot of confusion in Western societies. When people talk about wet markets in the American media, they are typically focusing on a subset with overpacked animal conditions, insufficient sanitary precautions, and wildlife trafficking or slaughter.

In fact, the “wet” in wet market is simply meant to contrast with a “dry” market where shoppers might find dry goods. Wet market is a term used for various kinds of meat and produce markets around the world, including Singapore, Japan, and the US itself.

As a columnist in Malaysia describes them, wet markets are places for fresh produce, and are commonplace all over Asia — he attributes the word “wet” to the fact that ice is often used to keep the food fresh while melting onto the floors.

Wet markets can sell fresh fruit and vegetables as well as meat.

The famous Tsukiji fish market, relocated and renamed in 2019 to prepare for the Olympics, has been one of the largest and acclaimed wet markets in the world.

Clearly, wet markets vary in their regulation by local government and corresponding levels of sanitation. Many wet markets do not sell live animals. Most do not sell exotic mammals or wildlife.

That being said, the American notion of wet markets does exist, and it is a source of grave concern. Besides the concerns about poaching and smuggling of endangered species, these wildlife

markets do indeed pose increased risks for public health due to gaps in sanitation and overcrowding of live animals.

Feng Gao, MD, professor at Duke University, studies the genomes of viruses like SARS-CoV-2 and HIV to determine the animal origins of infectious disease.

He said that “contact with wild animals may be more dangerous for contracting new infectious diseases since people don’t know what kind of infectious microbes they carry, like chimpanzees for HIV-1, mangabeys for HIV-2, ferrets for SARS and now bats/pangolins.”

But even zeroing in on wildlife markets ignores the size of the problem.

”Domesticated animals are not safe either,” said Dr. Gao, pointing to poultry and swine in the transmission of influenza.

Some slaughterhouses pack animals together tightly in far greater numbers than wet markets, creating seriousrisk factors for generation and transmission of new diseases from this huge reservoir of hosts.

And how many more slaughterhouses and deforestation zones are there in the world than wet markets? There are over 800 livestock slaughterhouses in the United States, with an additional 2900 poultry slaughterhouses, which in 2017 butchered 121 million hogs, 32 million cattle, and 9 billion chickens.

And as for forests, the world lost over 500,000 square miles of forest from 1990 to 2015, about twice the size of Texas.

The cry to end wet markets likely plays into the hope that there is an easy scapegoat, and that it is “foreign,” or at least on the margins of Western society.

Historian Xaq Frohlich of Auburn University said in an interview that “there is a long history of people seeking to blame pandemics on others.” He added that “People who externalize the threat and perceive an epidemic as being caused by some outside force are less likely to take measures to reduce their present risk or risk in the future.”

While the world is certainly looking to reduce risk, opponents of wet markets may be missing the point. The last two decades gives us examples of where pandemics originate.

Some pandemics originated in animals then began to spread quickly among humans. The 2003 outbreak of SARS was linked to a virus in civet cats and early cases were linked to traders and cooks in restaurants who may have handled civets for meat.

In 2009, “swine flu” was an outbreak of H1N1 influenza that combined flu from pigs, birds, and humans and may have resulted from the fact that pigs can simultaneously become infected with human, pig, and bird flu. In 2012, MERS was linked to domesticated camels and is believed to have crossed from them into humans. Ebola may have originated in bats.

On the other hand, Zika virus is primarily transmitted first from mosquitoes to humans (and then between pregnant mothers and their children).

George Rutherford, MD, Professor of Epidemiology of Biostatistics at UCSF, said that dangerous crossover events from animals to humans are “part random chance.”

He added that an important factor for pandemic potential is whether a disease is transmitted only from animals to humans or within humans.

“If you look at the case of influenza H5N1, which is just deadly for poultry, it’s not that hard to transmit to a human but very hard to transmit from human to human. If a disease can be transferred from human to human, that’s a problem,” he said.

According to the Centers for Disease Control, 3 of every 4 new infectious diseases for humans are zoonotic diseases, or diseases that pass between species. Understanding what activities increase risk for pandemic zoonotic illness is important for global health because we are not yet able to predict outbreaks precisely.

Practices associated with higher risk of zoonotic spread include deforestation, live animal markets, wildlife trade, as well as agricultural practices such as feeding beef to cows.

While SARS and perhaps COVID-19 were associated with wet markets in their origin, we cannot forget that industrial meat production helped give us swine flu and bird flu.

Because these practices are so entrenched, efforts have been redirected not to change them but to simply catch a pandemic earlier in its spread.

The Global Virome Project has been sampling viruses in animals worldwide and analyzing their genomes since 2018, aiming to stall pandemics by identifying high-risk viruses and tracking their growth among animal populations.

Still, it is clear that models have not yet been able to predict the appearance of diseases like H1N1 influenza or the current pandemic.

In China, officials have banned many wildlife for consumption, and wet markets in New York and California are under pressure to close. Unfortunately, public dialogue seems rooted in an oversimplified buzzword when we should be talking about the wildlife trade, and other risk factors as well.

“Minimizing direct contacts with live animals can significantly reduce the chance for zoonotic diseases,” saidDr. Gao.

The greatest dangers seem to exist in places where wild or domestic animals come into extended contact with humans. These include slaughterhouses as well as areas with rapid development into animal habitats.

While some high-risk wet markets pose a real threat to public health, this threat may be small compared to those of the wildlife trade at large and intensive livestock farming for meat.