Dr. Gary Green has been an infectious disease specialist for 25 years. In this quarter century, he has never seen the flu increase at this time of year – until now.
But it’s not just the strange, unseasonal rise in the flu that has Green, a doctor with Sutter Health, worried. The particular strain causing this spike is found to be highly resistant to the 2021-22 flu vaccine. This is happening during a time of high COVID transmission. And there is no clear picture on when either virus will peak.
Green was sufficiently alarmed that he sent an alert this week to other Sutter doctors, advising them to be on their guard.
“I want to warn our doctors, in case they want to do some advanced planning,” he told The Press Democrat. “It’s like in the ocean, when there are sleeping waves. If two waves hit at the same time, it is not good. I’m afraid it’s a dormant wave.
The California Department of Public Health issued a similar health advisory on Tuesday.
The bizarre timing of this outbreak of the H3N2 virus – one of two forms of influenza A, the other being H1N1 – continues a pattern that emerged during the coronavirus pandemic. It has become more difficult to predict outbreaks of communicable diseases.
A similar change happened in 2021 with respiratory syncytial virus, according to Dr. John Swartzberg, professor emeritus of infectious diseases and vaccinology at the University of California, Berkeley School of Public Health.
“It’s mostly a childhood condition, but older people can get it too, and it can be very serious when they get it,” Swartzberg said. “RSV is usually an autumn virus, but last year it appeared in late spring, early summer. One of the phenomena that we have seen with this pandemic is that it has changed the epidemiology of other diseases. It changes the seasonality.
Within the Sutter Health System, Green said, it’s considered “flu season” anytime more than 10% of all nasal and oral swabs test positive for the flu. This season usually arrives in November, peaks in late January or early February, and exits its “epidemic” phase in late March.
“It’s just kind of a rampant disease in the summer or early fall,” Green added.
Except 2022 breaks the mould. Instead of the sporadic cases of influenza A that Sutter would typically see at this time of year — “like maybe 0.1% of our swabs,” Green said — the supplier is finding positive rates approaching 15% in the Bay Area. The numbers would be higher than those in the San Joaquin Valley, a fact CDPH alluded to in its advisory.
The current flu rate in Sonoma County is undetermined. Unlike the coronavirus, the flu is not a reportable disease unless a person is hospitalized and under the age of 65, according to Lucinda Gardner, an epidemiologist with the County Health Services Department.
No one has proven direct causal links for the current influenza A spike, but experts seem to agree that it is linked to behavior change during the COVID pandemic.
The winter of 2020-21 saw “remarkably low incidence” of influenza, Swartzberg said, because “things that prevent COVID also prevent influenza.”
In other words, more people got the flu shot that year because they were panicked by the new respiratory disease that had swept the planet. Many were hiding and social distancing. Schools and churches stopped meeting in person.
A year later, Swartzberg said, health workers feared the 2021-22 season could explode with flu cases, especially if people let their guard down. Because so few had caught the flu the previous winter, immunity would be on the decline. Then the omicron COVID variant exploded and most people tightened their safety protocols again.
“But as the omicron dwindled and the government got rid of many mask mandates, our population started behaving like there was no more pandemic,” Swartzberg said. “Not only did omicron come back with a different variant, but we’re seeing the flu that we would have seen earlier this year.”
Worse still is the resistance that the H3N2 virus is showing to the current flu vaccine.
Each year, Green said, doctors from the World Health Organization, the US Centers for Disease Control and other major health organizations formulate a specific flu vaccine based on the latest research. It’s supposed to be effective against both types of influenza A and both types of influenza B, but it doesn’t always work that way.
“It’s really random,” Green said. “Probably every one to four years one of the strains doesn’t match the vaccine. And sometimes it’s not the predominant strain, so you hardly notice it. This year is kind of a perfect storm, where the dominant strain is the one that isn’t affected much by the vaccine.