
A seasonal flu virus that can lead to paralysis has been detected in California wastewater.
Influenza B has been shown at a “high” level over the last six weeks, according to recent data from Stanford University’s WastewaterScan.
The highly contagious respiratory virus triggers seasonal illness every fall and winter can also result in more severe and life-threatening conditions.
For example, it can trigger the rare Guillain-Barré Syndrome: a condition that causes muscle weakness and even paralysis. While the autoimmune disorder’s cause is not fully understood, the syndrome often follows infection with a virus.
Infection may also generate other neurological complications, including encephalitis. Encephalitis, which is swelling of the brain, can also lead to paralysis, seizures, and other issues.
While the less common influenza B — which only affects humans and mutates less easily — is not as likely to cause pandemics as is Influenza A, it can still result in outbreaks, according to the National Council on Aging. Furthermore, influenza B tends to circulate later in the flu season, often peaking in the spring.
Detection of the influence B virus comes on the heels of one of the Golden State’s deadliest flu seasons, with state officials tallying more than 900 deaths by February.
“There’s no doubt there’s a lot of respiratory viruses,” Dr. Monica Gandhi, a professor of medicine at UC San Francisco, told SFGATE.
And, influenza B isn’t the only respiratory virus Californians need to be concerned about.
While Covid cases have plummeted, cases of respiratory syncytial virus, human metapneumovirus, and Enterovirus D68 are also at levels deemed “high.”

EV-D68, which has no known cure, can cause polio-like paralysis in children. Levels of EV-D68 were rising in the Bay Area and Southern California last fall. RSV kills more than 100,000 infants worldwide each year and HMPV can result in bronchitis and pneumonia.
Plus, it’s possible to get a double infection. That’s even the case for both influenza strains.
However, data from the state’s Department of Public Health shows only a small percentage of eligible Californians have received the appropriate respiratory virus vaccines.
At the beginning of the month, the department reported that influenza activity was low.
“While the numbers are low, there’s still a lot of virus circulating and people getting sick,” John Swartzberg, a clinical professor emeritus at UC Berkeley’s School of Public Health, told SFGATE.