California is still experiencing its strongest summer surge in COVID-19 cases in years, and an unusual mid-summer mutation may be contributing to that.
Experts say there are several possible reasons for the worst summer surge in infections since 2022. Extreme heat and smoke from devastating wildfires have kept many Californians indoors, where the disease is more likely to spread, and it’s been a long time since most adults last had the coronavirus or their last vaccination, making them more vulnerable to infection.
However, changes in the virus have expanded the scope of its spread.
Of particular concern is the rise of a highly contagious subvariant called KP.3.1.1, which is highly contagious and is making even people who had avoided infection throughout the pandemic sick.
“COVID-19 is very common right now,” said Dr. Elizabeth Hudson, regional director of infectious diseases for Kaiser Permanente Southern California’s 16-hospital health system.
Hospitalizations due to COVID-19 are on the rise but remain lower than the summer peaks of the past two years, likely due to residual immunity and the widespread availability of anti-COVID-19 drugs such as paxlovir.
The World Health Organization has warned that coronavirus infections are rising around the world and expressed concern that more severe variants of the virus could emerge.
“In recent months, many countries have seen COVID-19 infection surges, regardless of the season, including during the Olympics,” said Dr Maria Van Kerkhove, WHO’s technical lead for COVID-19.
Among those caught up in the action was Noah Lyles, the 27-year-old American sprinter who narrowly missed out on a bronze medal in the 200-meter final on Thursday after winning gold in the men’s 100-meter final. Lyles collapsed after the race, suffering from shortness of breath and chest pains, and was later carried away in a wheelchair.
“It definitely affected my performance,” he said of the illness, estimating that he felt only “90 to 95 percent” recovered.
The percentage of positive COVID-19 tests has been trending upward for weeks, exceeding 10% globally and over 20% in Europe. In California, the COVID-19 positivity rate for the week ending August 5 was 14.3%, well above the peak of last summer and winter and up from 10% a month earlier.
There were already early signs of the usual midyear wave in the United States in May, as new COVID-19 variants, KP.2 and KP.1.1 (collectively known as FLiRT), began to rage, replacing the JN.1 strain that had been dominant during the winter.
But by July, there was a clear increase in the descendant strain, KP.3.1.1.
“KP.3.1.1 is extremely transmissible and somewhat immune evasive. It kind of emerged out of nowhere in the summer,” said Dr. Peter Chin-Hong, an infectious disease specialist at the University of California, San Francisco.
Kaiser Permanente Southern California Hospital is seeing an increase in cases, and “if we look at the CDC data, KP.3.1.1 is driving this surge,” Hudson said. “We’re definitely seeing more cases than we saw last summer.”
Anecdotally, some infected people report “actually feeling pretty ill and feeling really fatigued for the first two days,” Hudson said.
While people may want to think their symptoms are just allergies, “it’s probably COVID-19, which is why we really encourage people to continue to get tested,” she said.
But an initial negative test result is not necessarily a relief: authorities recommend repeat testing over a period of five days after symptoms appear to be sure.
It’s been four weeks since California reported “very high” levels of coronavirus in wastewater, following five weeks of “high” virus levels, according to data released Friday by the Centers for Disease Control and Prevention.
Last summer, California saw only eight weeks of “high” coronavirus concentrations in wastewater and never “very high.” In the summer of 2022, California saw 16 weeks of “high” or “very high” coronavirus concentrations in wastewater.
“Compared to this time last year, fewer people have been vaccinated this year,” Chin-Hong said, “which means people, especially the elderly, are less prepared to deal with this virus.”
According to the CDC, 44 states have “high” or “very high” levels of coronavirus in their wastewater. Five states and the District of Columbia have “moderate” levels, and there is no data available for North Dakota.
The CDC said coronavirus case numbers were “increasing” or “likely increasing” in 32 states, including California, “stable or uncertain” in seven states and the District of Columbia, “likely decreasing” in Connecticut, and “decreasing” in Hawaii and Nevada. Estimates were not available for eight states.
In Los Angeles County, wastewater coronavirus levels rose to 54% of last winter’s peak in the 10 days ended July 27, the most recent data available. A week earlier, wastewater coronavirus levels were 44% of last winter’s peak.
In the week ending August 4, Los Angeles County reported an average of 479 new coronavirus cases per day, double the number five weeks earlier. The number of cases is an undercount and reflects only tests administered in health care facilities, not self-tests administered at home.
In Santa Clara County, the San Francisco Bay Area’s most populous county, coronavirus levels were high in all sewer districts, including San Jose and Palo Alto.
Coronavirus-related hospitalizations and emergency room visits are also on the rise: In the week ending August 3, Los Angeles County hospitals were admitting an average of 403 coronavirus-positive patients per day. That’s double the number five weeks earlier, but only about 70% of last summer’s peak and only one-third of the peak in the summer of 2022.
In the week ending Aug. 4, 4% of emergency room visits in Los Angeles County were classified as coronavirus-related, more than double the figure seven weeks earlier, from a peak of 5.1% last summer.
“We’ve had some people who have become very ill with COVID-19, and they tend to be quite immunocompromised,” Hudson said.
The University of California, San Francisco, is also seeing an increase in the number of patients hospitalized with the coronavirus: Chin-Hong said there were 28 hospitalized patients as of Friday, up from fewer than 20 a week ago.
In the Bay Area, three counties are urging people to consider wearing masks in indoor public settings amid a surge in coronavirus cases. Contra Costa County Public Health said Tuesday it “recommends wearing masks in crowded indoor settings, especially for those at higher risk for severe illness if infected.” Health officials in San Francisco and Marin counties have made similar requests.
Compared to advice like washing your hands and staying away from sick people, suggesting that people wear masks may provoke strong opposition from some people.
“The moment people see this in their minds, it starts a chain reaction of all the negative things of the pandemic, like social shutdowns and social isolation,” said Dr. Abrar Karan, an infectious disease physician and researcher at Stanford University.
But masks do help reduce the risk of infection, and you don’t have to wear one all the time to reap the benefits. Curran says he socializes and dine indoors at restaurants, but he does wear a mask in other situations, including “when traveling” and, of course, at work.
Doctors say wearing a mask is one of many tools people can use to reduce their risk, and can be especially helpful when in crowded indoor spaces.
Curran said he has seen an increase in positive coronavirus cases during emergency care shifts and suggested more medical workers take the time to order tests, fearing patients coming in with relatively mild symptoms are being sent home without being tested.
But doing so could miss a potential COVID diagnosis and lead to patients receiving a prescription for an antiviral drug like Paxlobidi.
Without testing, “there’s a risk of taking shortcuts and not prescribing medications that technically should actually be administered,” Curran said.
Times reporter David Wharton contributed to this report from Saint-Denis, France.
