US health officials are growing concerned about this year’s flu season – and are already seeing signs the virus is spreading.
As the 2022-23 flu season begins, a high school in California is facing a “high rate of absenteeism” among its students due to possible cases of the flu. Influenza activity in the United States often begins to increase in October and typically peaks between December and February.
“We can confirm that there is a high rate of absenteeism at Henry High School due to probable influenza,” Samer Naji, a spokesman for the San Diego Unified School District, said in an email to CNN on Thursday. About 1,000 of 2,600 students were missing on Wednesday.
“So far, COVID tests have been negative, but several students have tested positive for the flu,” Naji said. “Typical signs and symptoms include cough, sore throat, runny nose, fever and other symptoms of upper respiratory infection. We are in close contact with San Diego County Public Health.”
San Diego County Public Health confirmed to CNN that it was investigating the major outbreak of respiratory and flu-like symptoms among students at Patrick Henry High School — and Del Norte High School in Poway, California.
“Del Norte High School (in the Poway Unified School District) was absent from nearly 400 students with cold and flu-like symptoms yesterday and Tuesday,” Poway Unified School District spokeswoman Christine Paik told CNN on Wednesday. “Health officials have informed us that cold/flu season is definitely here and is hitting schools harder now that COVID restrictions are no longer in place.”
San Diego County Public Health announced Wednesday that “it’s too early” to determine the cause of the outbreaks and that the county is conducting an assessment.
“We are coordinating with local school districts and checking with other campuses to find out why so many students are being affected so suddenly,” said Dr. Cameron Kaiser, the county’s assistant health officer, in an announcement on Wednesday.
“Unfortunately, we expected this to be a tough flu season, and other respiratory viruses besides COVID-19 are making a quick comeback,” Kaiser said. “If you haven’t already, now is the time to get vaccinated against flu and COVID-19 for the extra protection that vaccines offer.”
An early increase in seasonal flu activity has been reported in most parts of the United States, with the southeastern and south-central areas of the country reporting the highest flu levels, according to the US Centers for Disease Control and Prevention. More than a thousand patients were hospitalized with the flu this week, the agency said.
“Nationally, the percentage of samples testing positive for influenza in clinical laboratories is increasing; However, activity varies by region,” CDC researchers wrote in the agency’s latest weekly flu report, released Friday.
While current influenza activity overall is still low, the CDC report notes that activity is increasing in most parts of the country, with three jurisdictions showing moderate activity and six jurisdictions showing high or very high activity.
This week, 3.3% of respiratory samples sent to clinical laboratories tested positive for influenza, according to the new report. That’s a jump from the 0.1% of samples that tested positive this time last year and the 0.2% of samples that tested positive this time in 2020.
However, the new data suggests the nation may be returning to pre-Covid flu levels, as around this time in 2019 it was reported that 3.1% of samples had tested positive for flu.
The new CDC report also says that 1,322 patients with influenza were hospitalized this week and that there were three childhood influenza-related deaths this week.
Overall, the most commonly reported influenza virus this week was influenza A (H3N2), and 2.6% of outpatient visits to healthcare providers were for respiratory illnesses, which included symptoms such as fever and a cough or sore throat. This is above the national baseline of 2.5%.
“An annual flu shot is the best way to protect yourself from the flu. Vaccination helps prevent infection and can also prevent serious outcomes in people who get vaccinated but still get the flu,” the report said.
“CDC recommends everyone 6 months and older get a flu vaccine, ideally by the end of October. There are also prescription antiviral flu medications that can be used to treat influenza; these must be started as early as possible.”
It can be difficult to predict what influenza activity might be like in any given year, but doctors are bracing for a “very substantial” flu season, Dr. William Schaffner, professor in the Department of Infectious Diseases at Vanderbilt University Medical Center and medical director of the National Infectious Disease Foundation.
“I’m concerned that we’re going to have a very large influenza season this year, very different from our previous two seasons,” he said.
Signs of increased flu activity were first seen in the southern hemisphere this summer, and as more people in the northern hemisphere ease Covid-19 restrictions and socialize again without masks and in large crowds, flu cases are being reported. The nationwide number of cases so early in the flu season is unusual.
“Here we have mid-October — not mid-November — we’re already seeing scattered influenza cases, even influenza hospitals across the country,” says Schaffner, whose medical center at Vanderbilt University is part of a surveillance network that tracks hospitalized flu cases.
“So we know that this virus is already spreading in the community now. It’s already picking up speed. It seems to me that it’s about a month early,” Schaffner said.
When people began isolating, social distancing and masking to slow the spread of Covid-19 in early 2020, the flu all but disappeared in the US. As a result, most people have not been exposed to influenza for a number of years, meaning immunity to influenza viruses may be low, underscoring the need for vaccination.
U.S. health officials are encouraging people to get the flu shot as soon as possible, said Adriane Casalotti, director of government and public affairs for the National Association of County and City Health Officials.
“There is definitely pressure now to put the flu shot at the top of people’s priority lists. After seeing what’s going on in the southern hemisphere, in Australia, we’re all concerned that frankly, this year’s flu season could be very, very tough,” Casalotti said.
Concern has grown as officials also brace for possible surges this winter of Covid-19 and other common respiratory viruses such as respiratory syncytial virus, or RSV, a leading cause of lower respiratory tract infections in infants and young children.
Casalotti said the spread of influenza can have a significant impact on communities, especially as it can be difficult to distinguish flu symptoms from those of Covid-19, colds or allergies.
“We’re already starting to see the flu circulating in some areas,” Casalotti said. “Overall, flu activity is low nationwide, but it’s starting to rise, particularly in the Southeast.”
In August, as concerns grew about the coming flu season, the US Centers for Disease Control and Prevention’s Advisory Committee on Vaccination Practices released a report updating its recommendations for seasonal flu vaccination for this year.
Typically, older adults receive a higher dose of influenza vaccine than younger adults, but in the latest update, ACIP recommended that adults age 65 and older “preferably” receive a higher dose or an adjuvanted influenza vaccine.
“There are three of the influenza vaccines that have been shown to work better in people 65 and older,” said Schaffner, who is a liaison representative at ACIP. “There’s the high-dose vaccine, another that contains an adjuvant — an immune stimulant — and the third is a recombinant vaccine.” Recombinant flu vaccines do not involve the flu virus or chicken eggs in the manufacturing process.
“If you look back at people aged 65 and over in previous seasons, 80% of them already received one of these three vaccines,” he said. “New this year, ACIP has issued a highly preferred recommendation. They actually said that when vaccinating people aged 65 and older, preferably use one of these three vaccines and only if one of them is unavailable, use the regular vaccine.”
Overall, the CDC recommends that everyone 6 months and older get an annual flu shot, especially people who might be pregnant — because the vaccine protects not only them but their baby as well, Schaffner said.
“There’s an added benefit,” he said. “The antibodies produced in response to the vaccine partially cross the placenta and enter the newborn. So the newborn gets some of that protection for the first four to six months of life, before we can actively vaccinate the baby.”