While transmission of respiratory syncytial virus has begun to plateau in Santa Clara County, the county's top health official said Tuesday, Dec. 6, that COVID-19 and flu transmission continue to rise.

COVID-19 virus concentration in each of the county's sewersheds in San Jose, Palo Alto, Gilroy and Sunnyvale is at its highest level in months, according to county Health Officer and Public Health Director Dr. Sara Cody.

Those concentration rates are roughly on par with previous surges for now, but the COVID-19 levels in the Palo Alto sewershed — which includes the cities of Los Altos, Palo Alto and Mountain View — are higher than at any point in the pandemic, including the record highs during last winter's omicron variant surge.

COVID-19 levels in the San Jose sewershed, which captures water from roughly 75% of the county, are currently at roughly 84% of the county's omicron peak, but continue to increase rapidly.

Cody also noted that the current number of people with influenza-like illness is "unprecedented" for early December, and RSV, which causes infections in the respiratory tract, continues to affect a significant number of children across the county, even as transmission of the virus slows slightly.

"We not only have COVID, as we've had the last two winters, but we have flu and RSV and other viruses circulating as well," Cody said during a news briefing Tuesday morning. "So it's like a winter of viral soup."

Among county residents with the flu or other flu-like respiratory viruses, between 7% and 10% of children are currently being admitted to emergency rooms with flu symptoms, compared to less than 2% for adults.

Cody acknowledged a certain amount of fatigue toward COVID-19 and said she doesn't anticipate reinstating a countywide mask mandate or other public health measures, but did urge residents to take precautions during the holidays, particularly when indoors.

"Indoors is not really a safe place anymore, especially if it's crowded and there's a lot of people without masks," she said. "That's a really good time to choose to wear a mask."

Residents who have yet to get a flu shot or COVID-19 vaccine with an additional booster dose should also do so as soon as they can, Cody said.

To date, roughly 25% of eligible county residents have gotten the updated booster vaccine, which targets both the original COVID-19 strain and two subvariants of the omicron variant.

That vaccination rate increases among older age groups, according to Cody, but remains under 50% even among people ages 65 and up, who are most likely to become seriously ill or hospitalized with COVID-19.

She noted that while the vaccine does not completely eliminate a person's capacity to contract the virus, it does highly reduce a person's chance of becoming seriously ill with COVID-19 or dying because of it.

"That's just not going to get us where we need to be," Cody said of the relatively low uptake for the omicron booster. "That's not going to protect us, that's not going to protect our families and that's not going to protect our health care system."

County residents can contact their primary health care provider, retail pharmacies or visit the county's website at publichealth.sccgov.org/health-information/immunizations for information about getting a flu or COVID-19 vaccine.

Watch Tuesday's full news briefing: