The pesky flu virus has arrived in Northern California and while it's too early to know for sure, this could be a nastier than normal season.
The predominant circulating flu strain -- influenza A H3N2 -- has filled East Coast emergency rooms with achy, feverish people and has in other years brought more serious illnesses and hospitalizations.
Forty-one states now report widespread flu activity and 18 children nationwide have died. At least two people have died in California so far this season from flu-related complications.
"My clinic day is getting busier and busier," said Dr. Randy Bergen, a pediatric infectious disease expert at Kaiser Permanente Medical Center: Walnut Creek. "Our call centers are hopping."
The flu is arriving in California when many people are dealing with common colds, and another seasonal illness, respiratory syncytial virus or RSV, appears to be peaking.
That makes for a lot of runny noses and misery.
After a long day of treating sniffling, coughing children in his Oakland office last week, pediatrician Ricky Choi tweeted, "Is it just me or is this one of (the) worst cold and flu seasons in recent years?"
Most of the children Choi saw over the holidays had colds or RSV, a common cause of respiratory tract infections. But Choi is encouraging people to prepare for the flu.
"I have only seen one kid with flu-like illness in clinic so far, but it is coming and I feel a real urgency to get children and families vaccinated based on what we are seeing in other states," he said.
California now has regional flu activity, meaning that it has outbreaks in at least two regions, including the Bay Area, and it is expected to reach widespread status soon.
Kaiser keeps tabs on the virus with respiratory tests on patients and tracking hospitalizations and calls from its members.
"There's no question that the numbers are going up steeply, which is a concern," said Bergen, the clinical lead for Kaiser's flu vaccine program in Northern California.
About 13 percent of the people calling Kaiser's Northern California call centers are complaining about coughs, colds and the flu. That is 2 to 3 percent higher than previous years at this time.
Hospitalizations for pneumonia and flu-like illnesses are also rising. At the end of December, 6.2 percent of Kaiser's hospitalizations were for flu-related illnesses, up from 4.7 percent the week before.
And about 14 percent of Kaiser's respiratory tests are now coming back positive for influenza A, and 2 percent for influenza B. Kaiser considers the flu season to have arrived when positive tests exceed 10 percent.
Other organizations, however, have yet to see a significant number of flu-related illnesses.
"We are seeing some cases, but I would say less than two dozen since we started tracking back in October," said Dr. Yvonne Maldonado, chief of pediatric infectious disease at Lucile Packard Children's Hospital at Stanford.
It is a different story with RSV, however. Stanford treated 11 people for RSV from December 31 to Jan. 6, and a total of 63 people since Sept. 24.
"RSV is something that we have seen a lot of, but it looks like the cases are at a plateau right now," Maldonado said.
This year, the nation's flu season began in the Southeast in its earliest start in nearly a decade.
The good news is that the vaccine is a good match for this year's flu strains, particularly the H3N2 virus.
Vaccine is still available and experts say it is not too late to be immunized, but they encourage people to act quickly because it takes about two weeks to develop immunity.
Campbell resident Linda Walton, who did not get a flu shot because she is allergic to eggs, started feeling ill Sunday night with what she suspects was the flu.
"It's a funky kind of flu virus," she said. "I had the sniffles and was feeling achy, tired."
But she was on the mend by Tuesday. "I haven't had the flu in a long time," she said. "This seems milder than I've had in the past."
California has had relatively mild flu seasons for the past three years, and despite signs that this year could be rough, many experts are avoiding predicting what the fickle virus will do.
"I will never hazard any kind of a guess as to what will happen," Maldonado said, "because you have a pretty good chance of being wrong."
Sandy Kleffman covers health. Contact her at 510-293-2478. Follow her at Twitter.com/skleffman.
Contact your health care provider.
Many pharmacies offer shots for about $25.
Kaiser members can call 800-573-5811 or go to www.kp.org/flu.
Your local health department may offer free or low-cost shots.
Find nearby locations by going to http://flushot.healthmap.org.
The flu virus is spread by inhaling droplets coughed or sneezed into the air by an infected person or by coming into contact with their nasal secretions.
The illness often starts with chills, followed by a fever, headache, sore throat, cough, runny nose and muscle aches.
To get well, experts recommend resting, drinking plenty of fluids and avoiding exertion. Decongestants and antiviral drugs may also help.