Brenna Swift, The Union Democrat

Influenza is on the rise in the Mother Lode, and public health officials say more people could get sick in coming days.

The U.S. Centers for Disease Control and Prevention declared an influenza epidemic nationally Friday and said California is one of only three states without "widespread flu activity."

Yet the sickness appears to be gaining a foothold in the Mother Lode and other parts of California, with more positive tests for influenza within the past week.

"California has still been sort of spared at this point, but we're prepared for some increasing flu activity if it goes along with what's happening in the rest of the country," said Calaveras County Public Health Officer Dr. Dean Kelaita.

Influenza is a contagious respiratory illness caused by Influenza A or Influenza B viruses. A third type, Influenza C, is not thought to cause epidemics. Influenza A is divided into two subtypes, H3N2 and the new version of H1N1 known as the "swine flu."

H3N2 is believed to be the predominant flu strain driving outbreaks in states such as New York, which has declared a public health emergency.

Instances of Influenza A H3N2 in Tuolumne County have increased. Five of eight tests conducted Jan. 13 were positive for Influenza A. The figure comes at a time when many Mother Lode residents say they or their co-workers are sick.

Mark Twain Elementary School had 51 of its 555 students absent Monday morning, double its normal number of absences. Several parents who called the school office said they thought their children had the flu.

Twenty-two students went home sick from Summerville Elementary School on Jan. 9 and 48 the next day, though Superintendent Leigh Shampain said many were suffering from a stomach illness rather than influenza. Its total enrollment is about 350.

The school has brought in extra custodians to clean classrooms and reduce the spread of illness, he said.

Brad Morrison, a registered nurse and director of emergency services at Sonora Regional Medical Center, said the hospital's emergency room has treated many patients with "influenza-like illness."

More influenza tests are being ordered because of media reports and heightened awareness of the flu, Stolp said. Symptoms include cough, sore throat, stuffy nose, headaches, muscle or body aches, and fever, although not everyone infected will get a fever.

The typical incubation period for influenza viruses is one to four days, according to the U.S. Centers for Disease Control and Prevention.

Young children, people 65 and older, and those with chronic health conditions are more prone to flu complications such as pneumonia and bronchitis. While most affected by the flu will recover in a few days to two weeks, it can prove fatal in some cases.

Public health officials are urging people to get influenza vaccines as soon as possible. The CDC recommends that everyone 6 months of age and older get a vaccine.

The vaccine takes about two weeks to provide full protection, and a CDC study pegged its effectiveness at about 62 percent. That's still enough to prevent disease on a community-wide level, Stolp said.

The Calaveras County Public Health Department has influenza vaccines on hand and is making sure local providers are well-stocked.

The Tuolumne County Public Health Department holds a flu shot clinic starting at 1 p.m. every Tuesday and is gearing up for what it expects to be an above-average turnout today.

Interest in flu shots has been "steadily going up week by week," said Dawn Foster, a licensed vocational nurse at the Tuolumne County Public Health Department.

Stolp said getting vaccinated is the No. 1 flu prevention step, followed by regular hand washing. If soap and water isn't available, hand sanitizer with at least 60 percent alcohol content is the next-best alternative.

Those who are sick should stay home from work or school to avoid passing the flu on to others.

Stolp recommends that people see a doctor if they experience shortness of breath, a worsening cough, or a fever that doesn't subside. Patients with preexisting conditions, such as heart problems, should be especially vigilant about going to the doctor.

The flu can be treated with antiviral medications, but they should generally be started within 48 hours of getting sick with influenza, Stolp said.