The coronavirus pandemic that has crippled major retailers and small shops worldwide may be making a dent in illicit business, too.

In Chicago, one of the most violent places in the US, drug arrests in the weeks since the city shut down are down by 42% compared with the same period last year.

Some criminal lawyers say part of the reason for that decrease is that dealers have no choice but to wait out the economic slump.

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

Overall, Chicago’s crime declined by 10% after the pandemic struck, a trend that is playing out globally. 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 are lifted 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’s 1990s crime decline, one of the biggest turnarounds in US history, crime dropped by about 40% over three years.

Across Latin America, crime is down to levels unseen in decades. El Salvador, for example, reported an average of two killings a day last month, down from a peak of 600 a day a few years ago.

Eduardo Perdomo, a 47-year-old construction worker, said while getting off a bus in San Salvador, the capital of El Salvador. “I think they [gang members] are afraid of catching the virus, and they aren’t going out.”

Much of the decrease is down to tougher security policies and gang truces. But the imposition of near-total limits on movement is likely to be driving it down further, according to analysts and national statistics.

In Peru, crime levels fell 84% last month. Raúl González, a mortician in Lima, usually has as many as 15 bodies a day, many of which 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,” González said.

In South Africa, police reported a big decline during their first week of lockdown measures. The country’s police minister, Bheki Cele, said reported rapes fell to 101, from 700 over the same period last year. Serious assault cases fell from 2,673 to 456, and murders from 326 to 94.

In New York, which has the most cases of coronavirus in the US, major crimes such as murder, rape, robbery, burglary, assault, grand larceny and car theft decreased by 12% from February to March. In Los Angeles, statistics for key crimes were consistent with last year’s figures until the week of 15 March, when they dropped by 30%.

“There’s a lot fewer opportunities for criminals to take advantage of,” said Joe Giacalone, a former New York police department sergeant who now teaches at John Jay College of Criminal Justice. “Most burglars, they wait for you to leave the house.”

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 off work due to illness, and more than 2,000 diagnosed with Covid-19.

US authorities say they are issuing citations instead of making low-level arrests, policing physical 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,” said Philip Stinson, a criminologist at Bowling Green State University. “In many respects, over the next weeks they’re really in survival mode.”

Play Video 0:47 Drone footage shows San Francisco deserted under coronavirus lockdown – video

While narcotics arrests are down, drug sales continue, with dealers probably changing 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 Maryland man accused of operating a dark web 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 is [expletive] up inventory”, according to court documents.

Other crimes, however, may be fuelled by shutdown orders. Houston’s police chief, Art Acevedo, said aggravated assaults in the city were up 10% 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 hit the state. Advocates said the calls were not being made because children were not in school.

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

In San Jose, California, the 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.”