The coronavirus pandemic that has crippled big-box retailers and mom-and-pop shops worldwide may be making a dent in illicit business, too.

Chicago

In Chicago, one of America's most violent cities, drug arrests have plummeted 42 percent in the weeks since the city shut down, compared with the same period last year.

Part of that decrease, some criminal lawyers say, is that drug dealers have no choice but to wait out the economic slump.

Dallas ISD police officers Mylon Taylor, left, and Gary Pierre push a car that ran out of gas while waiting in line for the weekly school meal pick up for students in Dallas, amid concerns of the spread of COVID-19. (AP)

"The feedback I'm getting is that they aren't able to move, to sell anything anywhere," Joseph Lopez, a criminal lawyer in Chicago who represents reputed drug dealers, said.

Overall, Chicago's crime declined 10 percent after the pandemic struck , a trend playing out globally as cities report stunning crime drops in the weeks since measures were put into place to slow the spread of the virus.

Even among regions that have the highest levels of violence outside a warzone, fewer people are being killed and fewer robberies are taking place.

Still, law enforcement officials worry about a surge of unreported domestic violence, and what happens when restrictions lift – or go on too long.

It's rare for a city to see a double-digit drop in crime, even over a much longer period. During New York City's 1990s crime decline, one of the biggest turnarounds in American history, crime dropped about 40 percent over three years.

That makes the drop-offs occurring now – in a period of just a couple of weeks – even more seismic.

Detroit Police Capt. Jevon Johnson, right, talks with Lt. Pride Henry outside the TCF Center, in Detroit (AP)

Latin America

Across Latin America, crime is down to levels unseen in decades.

"Killings are down, and the gangsters aren't harassing so much,'' Eduardo Perdomo, a 47-year-old construction worker, said while getting off a bus in San Salvador.

"I think they're afraid of catching the virus, and they aren't going out.''

El Salvador reported an average of two killings a day last month, down from a peak of 600 a day a few years ago.

Much of the decrease has taken place because of tougher security policies and gang truces.

But the imposition of near-total limits on movement is likely driving it down further, according to analysts and national statistics.

In Peru, where crime levels fell 84 percent last month, Lima mortician Raúl González usually has as many as 15 bodies a day – many are homicide victims. This week he napped on a bench after six hours without a client.

"There are almost no killings or car accidents these days,'' Mr González said.

Epifanio Gizaldo waits for clients inside the Candelaria Funeral Home, during a nationwide lockdown imposed by the government due to the COVID-19 pandemic in Lima, Peru. (AP)

South Africa

In South Africa, police reported a stunning decline during their first week of lockdown measures.

Police Minister Bheki Cele said reported rapes were down from 700 to 101 over the same period last year.

Serious assault cases plummeted from 2673 to 456, and murders fell from 326 to 94.

New York

The US virus epicentre in New York saw major crimes – murder, rape, robbery, burglary, assault, grand larceny and car theft – decrease by 12 percent from February to March.

In Los Angeles, 2020 key crimes statistics were consistent with last year's figures until the week of March 15, when they dropped by 30 percent.

"There's a lot fewer opportunities for criminals to take advantage of," Joe Giacalone, a former New York Police Department sergeant who now teaches at John Jay College of Criminal Justice, said.

"Most burglars, they wait for you to leave the house."

A Tesla police car sits in front of the City/County Building after red and white lights were illuminated to show support and gratitude for first responders and medical personnel during the outbreak of the new coronavirus in Denver. (AP)

Policing has also changed in the face of the pandemic. Officers are increasingly getting sick; the NYPD, the country's largest department with more than 36,000 officers, has more than 7,000 officers out and more than 2000 diagnosed with COVID-19.

And US authorities say they're issuing citations instead of making low-level arrests, policing social distancing and putting detectives into patrol cars – which could, in turn, bring down crime rates.

While departments are unlikely to announce they've backed off policing certain crimes, "that's going to be the case", Bowling Green State University criminologist Philip Stinson said.

"In many respects, over the next weeks, they're really in survival mode," he said.

But while narcotics arrests are down, drug sales continue, with dealers likely forced to change their strategies, said Rodney Phillips, a former gang member in Chicago who now works as a conflict mediator in the city.

"These guys already face poverty and death in these areas," he said.

"They might be selling more online now. But they aren't going to give up just because of the coronavirus."

A police officer stands guard as he enforces curfew due to the new coronavirus pandemic, in El Callao, on the outskirts of Lima, Peru. (AP)

Wider USA

A Maryland man accused of operating a Darknet store selling prescription opioids boasted on his vendor page: "Even with Corona Virus the shop is running at full speed".

He told an undercover FBI agent he was just waiting for a shipment because "this corona virus (sic) is (expletive) up inventory", according to court documents.

Other crimes, however, may be fuelled by shutdown orders.

Houston Police Chief Art Acevedo said the city's aggravated assaults were up 10 percent in the last three weeks, and half of those were domestic violence, a significantly higher proportion than normal.

Calls to Missouri's child abuse and neglect hotline dropped by half as the virus first struck the state. Advocates said the calls aren't made because the kids aren't in school.

Tops tips for minimising coronavirus transmission. (9News)

And Chicago did see a spike in gun violence this week, according to the Chicago Sun-Times, which reported 60 shootings – 19 fatal – between Sunday and Thursday.

San Jose, California, Police Chief Eddie Garcia hopes the downward trend will continue after the pandemic is over. But his officers are preparing for the worst.

"The longer we're in a lockdown," he said, "the more we're playing with fire".

For most people, the coronavirus causes mild or moderate symptoms, such as fever and cough. But for others, especially older adults and people with health problems, it can cause severe symptoms like pneumonia.

More than 1.5 million cases have been diagnosed worldwide.

Key information about the coronavirus pandemic. (9News)

Coronavirus: what you need to know

How is coronavirus transmitted?

The human coronavirus is only spread from someone infected with COVID-19 to another . This occurs through close contact with an infected person through contaminated droplets spread by coughing or sneezing, or by contact with contaminated hands or surfaces.

How can I protect myself and my family?

World Health Organisation and NSW Health both recommend basic hygiene practices as the best way to protect yourself from coronavirus.

Good hygiene includes:

Clean your hands thoroughly for at least 20 seconds with soap and water, or an alcohol-based hand sanitiser;

Cover your nose and mouth when coughing and sneezing with tissue or your elbow;

Avoid close contact with anyone with cold or flu-like symptoms;

Apply safe food practices; and

Stay home if you are sick.