Here is the scene at the "wet markets" of China, where crowded, unsanitary conditions apparently helped launch the novel coronavirus pandemic that has upended life in the U.S. and led to "social distancing"

A wet market in China

How did the coronavirus pandemic get started? We do not have a definitive answer to that question, but scientists believe it can be traced to the "wet markets" of China. That raises this question: What is a wet market, why are they called that, and how did they prove to be an incubator for the worst public-health crisis of our lifetimes? Specifically, the Huanan Seafood Wholesale Market in Wuhan might have been the launching point for the novel coronavirus; it was shut down on January 1.

Jason Beaubien, global health and development correspondent for NPR, traveled to China in early January and got a firsthand look at wet markets. His report -- "Why They Are Called 'Wet Markets' and What Health Risks They Might Hold" --could be the definitive account, so far, of the environment that apparently launched a global pandemic.

How did it happen? First, it's important to note differences between "wet markets" and "wildlife markets." Wet markets generally sell fish, poultry, meat -- staples of the Chinese diet. In a "wildlife market," wild animals (bats, snakes, crocodiles, pangolins) are introduced to the environment -- in cramped conditions, in densely populated areas. That appears to be a recipe for zoonotic diseases, which jump from animals to humans. Reports Christopher St. Cavish The Los Angeles Times:

The issue, according to numerous op-ed articles, is when wildlife is introduced into this system. Rightly, critics note that bringing stressed animals of different species, who are all shedding different diseases, into close proximity and without any supervision, is, let’s say, not good for hygiene. At worst, it may provide the breeding ground for COVID-19, SARS and the avian flu.

Chinese culture certainly includes a taste for exotic meat, as St. Cavish reports, but it is not limited to China:

The attention-grabbing koala and wolf cub price list touted in Western media is likely exaggerated, but the general point remains true: China has a taste for exotic meat. In my 15 years in China, I’ve been offered camel hump at a major Chinese chain, muntjac at a secret wild game restaurant in Pudong and legal peacock in Yunnan, have watched a bamboo rat butchered and cooked by a popular online chef and seen a crocodile, mouth tied shut, hidden under a bench at a downtown Shanghai seafood market. Snake is more than a delicacy; by one count, Shanghai has more than 800 shops serving water snakes, king snakes and more.

Yet a taste for the exotic is not the problem. Where I’m from, in South Florida, people now patrol backyards in search of iguanas for the dinner table; restaurants serve BBQ alligator ribs; and it’s possible to order overnight delivery of muskrat, bobcat and rattlesnake on the internet.

Beyond meat that tastes good, at least to someone, an interest in exotic meats is rooted in homology beliefs extending back to “The Yellow Emperor’s Inner Classics,” which codified the medicinal philosophy more than 2,000 years ago; the idea that eating exotics confers wealth and status on the buyer; and the belief that certain wild animal parts have therapeutic effects (pangolin meat relieving rheumatism, for example). Weak legal controls push the sale of even the less exotic meats such as venison and pheasant into an unregulated and unsupervised gray area.

A more detailed account of the hygiene problems that can arise from wildlife markets can be found at "Bats Are Not To Blame for Coronavirus. Humans Are," at CNN. So, wildlife markets probably are the real problem, but they still get mixed up with wet markets, likely because both have open-air origins.  NPR's Beaubien describes what he saw in China, in an article posted February 8:

A "wet market" in Wuhan, China, is catching the blame as the probable source of the current coronavirus outbreak that's sweeping the globe.

Patients who came down with disease at the end of December all had connections to the Huanan Seafood Market in Wuhan China. The complex of stalls selling live fish, meat and wild animals is known in the region as a "wet market." Researchers believe the new virus probably mutated from a coronavirus common in animals and jumped over to humans in the Wuhan bazaar.

What is the scene like in a Chinese wet market? Beaubien describes it:

I visited the Tai Po wet market in Hong Kong, and it's quite obvious why the term "wet" is used. Live fish in open tubs splash water all over the floor. The countertops of the stalls are red with blood as fish are gutted and filleted right in front of the customers' eyes. Live turtles and crustaceans climb over each other in boxes. Melting ice adds to the slush on the floor. There's lots of water, blood, fish scales and chicken guts. Things are wet.

At the Tai Po market, a woman who runs a shellfish stall — she only wants to give her name as Mrs. Wong — says people blame wet markets for spreading disease. But she says that's not fair. Like just about everyone else in the market. Wong is wearing a surgical face mask because of the coronavirus outbreak. She's heard about the links between the wet market in Wuhan, China, and the coronavirus but doesn't think something like that would happen in Hong Kong.

"It's much cleaner in the Hong Kong markets. It's so different from what's happening in mainland China," she says. "When I go to mainland China and I'm trying to eat something, I'm concerned about what's in the food."

Wet markets and wildlife markets hardly are found only in China, reports Beaubien:

Meanwhile, this kind of market is not just an Asian phenomenon. There are similar markets all over the world — places where fish, poultry and other animals are slaughtered and butchered right on the premises.

But researchers of zoonotic diseases — diseases that jump from animals to humans – pinpoint the wet markets in mainland China as particularly problematic for several reasons. First, these markets often have many different kinds of animals – some wild, some domesticated but not necessarily native to that part of Asia. The stress of captivity in these chaotic markets weakens the animals' immune systems and creates an environment where viruses from different species can mingle, swap bits of their genetic code and spread from one species to another, according to biologist Kevin Olival, vice president for research at the EcoHealth Alliance. When that happens, occasionally a new strain of an animal virus gets a foothold in humans and an outbreak like this current coronavirus erupts.

As for the market in Hong Kong, its offerings are tame compared to those found in Mainland China:

The Tai Po market in Hong Kong does have some live animals besides the seafood but the selection is rather boring compared to the exotic assortment of snakes, mammals and birds on offer in some markets in mainland China. They're known to sell animals such as Himalayan palm civets, raccoon dogs, wild boars and cobras.

The only live birds in Tai Po are chickens, which are kept behind the butchered pork section of the market.

Chicken is becoming increasingly popular at the Hong Kong market:

Chan Shu Chung has been selling chicken here for more than 10 years. He says business is really good right now because the price of pork — his main competition — is through the roof. Pork is in short supply due to trade tensions between China and the U.S. and a recent bout of swine flu.

So people are buying more chicken. Customers can select a live bird from Chung's cages. Chung pulls them out by their feet, holds them upside down to show off their plump breasts. If the customer is happy with the bird, Chung puts a plastic tag with a number on the chicken's foot. He gives the customer a matching tag, sort of like a coat check. Fifteen minutes later the shopper can come back and pick up the chicken meat.

Chung says he and his colleagues do their best to keep the area clean. They wash down the stalls regularly and disinfect the countertops to stop germs from spreading.

Chung, however, is one of the few people in the market who is not wearing a face mask. Face masks have become so common in Hong Kong since the coronavirus outbreak started that pharmacies across the city are sold out of them.

Chung says he isn't afraid of this new coronavirus. He always gets his annual flu shot so he believes he's protected against this new disease, even though scientists say the flu shot will not protect people against this new coronavirus.

Chung adds confidently that he's even immune to SARS — for which there also is no commercially available vaccine.

But he does keep his chicken stalls incredibly clean, which public health officials say is one important step in stopping the spread of diseases. So maybe he's on to something.