A recent disruption in mail service to Cape Elizabeth illustrates the impact of COVID-19 on the U.S. Postal Service, officials say.

Not only has use of the mail system surged because of the pandemic and the holidays, but some carriers have missed work because they either got the virus or been forced to quarantine after coming into contact with someone who tested positive, USPS regional spokesman Steve Doherty said.

However, a representative of the union that represents Maine mail carriers said management’s failure to address chronic staffing shortages, not the pandemic, are really to blame for the inability to keep up with the demand on the system.

Doherty suggested COVID-19 was behind some mail delays in Cape Elizabeth last week, when some residents reported not receiving mail or not having outgoing mail picked up on Monday. Calls to the post office about the delays were answered with a recording saying the post office was experiencing delivery problems related to COVID-19, but no further information was provided.

Doherty did not specifically say that a carrier whose route includes the town had contracted the virus or was quarantining, but he did say the system is “struggling with employee leave” due to the pandemic.

“This did result in some delays on Monday in Cape Elizabeth, but they are current at this point,” Doherty said Thursday.

Doherty also said heavy volume due to packages may have also played a role in the delays. It wasn’t clear how widespread the impact has been. Doherty couldn’t be reached for further information Friday.

But the head of the local carriers’ union said the Postal Service has had staffing problems for years due to low pay, long hours and physically demanding jobs.

“We just can’t keep anybody,” said Mark Seitz, president of the Portland local of the National Association of Letter Carriers.

Seitz said starting pay for letter carriers of $17.29 an hour isn’t much above minimum wage levels and the job is difficult, especially during December, when carriers have to deliver thousands of packages along with letters, bills and regular mail.

Seitz said he knows of only a handful of carriers or supervisors who have tested positive for COVID-19 or were quarantining in the last couple of months and he said postal officials who blame the pandemic for delivery problems are either mistaken or being misleading.

He said staffing shortages have been chronic for at least the last eight years or so. In addition to low pay, he said, carriers have little control over their schedules and can be forced to work long hours and stretches of weeks without a day off, leading many to quit the job.

Seasonal factors are also a problem, Seitz said. In addition to heavy volume associated with the holidays, sometimes carriers have to stop early due to winter darkness. For instance, if a mailbox is attached to a house and no outside light is on, it can be difficult to locate the box and dangerous to try to walk up a long drive in the darkness.

That means carriers have to pick up the route the next day where they left off and deliver two days’ worth of mail for the stretches they missed the day before, and that can lead to further delays, Seitz said.

Seitz also said some residents might be confused if they see a rental truck pull up to a house to deliver a package. Seitz said the USPS rents the trucks to handle large loads of packages that are a big part of December deliveries.

The pandemic is straining both the mail system and the private shipping companies, and the holiday season has added to that. People are buying more products online to avoid having to go to grocery or big box retail stores, a trend that is carrying over into holiday gift shopping.

On Thanksgiving weekend, online shopping grew by 44 percent over last year, totaling nearly 100 million shoppers. That generates millions of packages to be shipped to consumers.

Last week, private shipping company UPS briefly suspended pickups from some retailers, including L.L. Bean in Freeport, because of the high volume of packages in its system. The company said it has agreements with major retailers to suspend service briefly when overall volumes hit certain benchmarks and retailers reported that online sales were stronger than ever over the long Thanksgiving weekend.