A 'perfect storm' of pandemic fatigue, crowded housing, and a new variant turned LA into a coronavirus epicenter

• Los Angeles has seen more coronavirus cases and deaths than any other county in the US.
• The majority of LA infections were recorded during a deadly winter surge over the last two months.
• Epidemiologists say a few factors turned LA into a coronavirus epicenter: the emergence of a local variant, escalating pandemic fatigue, and a high share of overcrowded multi-generational homes.

Scientists repeatedly warned that the winter holidays would usher in disastrous spikes in coronavirus cases across the US. But few places suffered as gravely as Los Angeles, now the epicenter of the nation's outbreak.

LA County has recorded nearly 1.1 million cases and 16,000 deaths to date - more than any other county in the US.

Things turned particular dire in early December, when LA moved into California's "extremely high risk" tier - an indication that the virus was spreading widely in the community. That meant most schools would have to suspend in-person learning. The following day, Gov. Gavin Newsom instituted a regional stay-at-home order that put a stop to outdoor dining and forced businesses like hair and nail salons to close.

LA's average daily coronavirus deaths quadrupled from December to January, while hospitalizations rose from around 2,500 per day to 7,500 per day.

By mid-December, Southern California ICUs were at full capacity. New daily cases in LA County hit an all-time high of more than 22,500 on January 4. Two days later, the county recorded more than 8,000 hospitalizations and 227 deaths - its highest counts ever.

Epidemiologists say there's no simple answer for why the crisis escalated so quickly.

"Nothing happens in a vacuum and there were probably a number of different factors that are at play here, including a more contagious variant," Dr. Anne Rimoin, an epidemiology professor at UCLA Fielding School of Public Health, told Insider.

"Los Angeles is a complex city," she added. "We have a large geography, a dense population, but more importantly, overcrowding plays a major role here."

Like many people across the country, Rimoin said, LA residents may also suffer from pandemic fatigue, which makes them less likely to abide by public-health recommendations.

"All of this together creates the perfect storm," she said.

That storm isn't necessarily over, though daily cases in LA have declined in the last week.

"Just because we're seeing this particular surge from the holidays start to go down," Rimoin said, "it doesn't mean that we're out of the woods."

An LA variant was spreading rampantly by December

The majority of LA's coronavirus infections have been recorded in the last two months. This deluge of cases coincided with the emergence of a local variant called CAL.20C.

In a study that's still awaiting peer review, researchers at LA's Cedars-Sinai Medical Center suggested that "the CAL.20C strain may be partially responsible for the magnitude of the surge in COVID-19 on the West Coast of the US."

By December, 36% of virus samples from Cedars-Sinai COVID-19 patients were identified as CAL2.0C. The variant also represented nearly one-quarter of all samples from Southern California.

Researchers still aren't sure whether CAL.20C spreads more easily than the original strain, but it does have a hallmark of more infectious variants: mutations that alter the spike protein, which the coronavirus uses to invade cells.

Still, scientists caution against pitting the blame for LA's outbreak on a single variant, since it's impossible to know how many variants are circulating at the moment.

"We've had zero situational awareness for so long because we haven't had enough sequencing, and the funding for sequencing has been nonexistent," Rimoin said. "We were lucky that Cedars-Sinai was able to do some of this on their own."

Other more infectious variants, like the B117 variant first discovered in the UK, might also have been spreading far either than scientists realized.

LA reported its first case of B117 on January 16, but Mayor Eric Garcetti told the Los Angeles Times that he suspected B117 was a factor in doubling LA's case count in December.

"Everybody I talked to said this acceleration was beyond any model and any expectation, so then people say, 'What broke down?' and I've got to think it's partly the strain that was out there," Garcetti said.

Even with vaccinations underway, Rimoin added, new variants could further exacerbate LA's outbreak.

"We now know that there are more contagious variants that are circulating and we may very well see this trend continue," she said. "We could see another surge as the UK variant or Brazil or South African variants become more dominant."

Overcrowded multi-generational homes have likely fueled transmission

With more than 10 million residents, LA County is the most populous county in the nation. Unsurprisingly, most of its cases have been concentrated in high-density urban areas where lots of people live and work. The nature of these living environments may have played a key role in facilitating the virus' spread.

On average, each household in LA County contains about three people - higher than the national average of 2.5 people per home.

A 2016 analysis from the real estate website Trulia found that 7% of households in the city of LA contained at least two generations. Only five other cities in the US had a higher share of multi-generational homes at the time. Yawar Charlie, director of the estate division at Aaron Kirman Group in LA, recently told Forbes that the demand for multi-generational homes in LA has only increased since the start of the pandemic.

In many cases, these homes are overcrowded - meaning they have more than one person per room, excluding bathrooms. Data from the US Census Bureau suggests that 11% of homes in LA County are overcrowded - the highest share of any major metropolitan area in the US.

Studies have suggested that overcrowding is a key contributor to coronavirus transmission. A June analysis found that California neighborhoods with the worst coronavirus outbreaks had three times the rate of crowding in households compared to neighborhoods that were largely spared.

But households still need to interact with other members of the public for community transmission to occur. Rimoin said it's possible that LA's essential workers are getting exposed at work, then bringing the virus home. More than half of LA County workers are employed in the service industry, in fields like food service, hospitality, residential construction, or personal services.

"We have a lot of essential workers, so they go home to multi-generational, overcrowded households, and have nowhere to quarantine appropriately," Rimoin said. "So of course the virus is going to spread rampantly."

Pandemic fatigue continues to drive cases

As the pandemic dragged on in October, public-health experts began to worry that people were becoming more lax about personal safety measures. A WHO report that month found that a growing share of European residents weren't sufficiently following lockdown restrictions or were decreasing their efforts to keep informed about the pandemic. Researchers detected similar patterns in the US as well.

"It appears that people are wearing masks and socially distancing more frequently as infections increase, then after a while as infections drop, people let their guard down and stop taking these measures to protect themselves and others - which, of course, leads to more infections," Dr. Christopher Murray, director of the University of Washington's Institute for Health Metrics and Evaluation, said in October.

Pandemic fatigue only seems to have worsened since then, with some LA residents actively challenging local mask recommendations.

In early January, anti-mask protesters stormed LA's Century City mall with megaphones, demanding that customers and employees remove their face coverings. The incident, along with several others, prompted the LA City Council to call for an ordinance that would fine those who refused to wear masks in an indoor public place.

"Widespread non-compliance is driving this unimaginable spread and there is no sign of slowing anytime soon," Paul Koretz, an LA City Council member, said at a January 13 meeting. "People who are alive and well right now, today, have a disastrously high risk of becoming infected - or dying - by Valentine's Day."

Rimoin also cautioned that pandemic fatigue was a prevailing danger in LA.

"When you have more contagious variants circulating and people now feeling free to do things that they weren't able to do for a while, we do risk having another surge happen in the near future," she said.

That outbreak, she added, wouldn't be relegated to LA alone.

"If anything, this pandemic has really laid clear that an infection anywhere is an infection everywhere," Rimoin said. "It would be foolish to think that what's happening in LA County is staying in LA County."