An ambulance took her to the hospital, where she was definitively diagnosed with the flu — and then with viral pneumonia. She also learned that her home thermometer was broken: It had read 99 degrees, but the doctors told her she was running a fever of 103.9 when she was brought in.
After five days in the hospital and two weeks out of work, Peterson is back in the office. But it hasn't been easy.
"It was horrible," she said. "All your energy is drained."
Peterson's story is an unusually dramatic one, and it also reflects something unusual about this season's flu: It started early. Influenza tends to begin hitting hard in February, but this year it came to town around the start of January in many states, according to the Centers for Disease Control and Prevention (CDC). Stories hit the media; readers got worried; and the demand for flu shots went up.
While the flu season seems to have peaked in other parts of the country, reported activity is still high in California. "It's definitely here," said pediatrician Ross DeHovitz of the Palo Alto Medical Foundation.
The exact number of flu cases in Santa Clara County is impossible to come by. Many people with the flu stay home and recover without ever seeing a doctor, and not every sick person gets tested for the flu. But several indicators are up. All the hospitals in the county have been reporting about 20 to 30 percent more people than usual coming into their emergency rooms, many with flu or flu-like symptoms, county health officer Marty Fenstersheib said.
"That's to be expected in the winter," he said, but added: "We know that this is a bit more than last year. ... We've had some reports of severe cases."
At press time, four cases of severe influenza and two flu-related deaths had been reported in Santa Clara County so far this season in people under 65. The county typically receives reports of severe cases in only the under-65 set but did also report the flu-related death of a 98-year-old woman a few weeks ago.
"It was our first death, so we chose to report it to bring more awareness," Fenstersheib said.
Statewide, 18 influenza-related deaths in people under 65 (including one pediatric death) have been reported this season as of Feb. 2, according to the most recent report from the California Department of Public Health Influenza Surveillance Program. The collaborative effort includes the CDC, Kaiser Permanente and various participating laboratories.
Nationwide, the CDC has reported 59 pediatric deaths related to flu this season. In the U.S. population as a whole (at least as reflected in the CDC's 122-city reporting system), 9 percent of deaths in the country for the week ending Feb. 2 were due to pneumonia and influenza. That's above the CDC's "epidemic" threshold but down from the previous week's 9.4 percent.
Officials say these numbers pale in comparison to the pandemic of 2009, when H1N1, a new strain of influenza, hit. The CDC estimated that H1N1 caused "between about 8,870 and 18,300" deaths from April 2009 through April 2010 across the country, with perhaps hundreds of thousands of hospitalizations.
That season, 282 flu-related deaths were reported in children in the U.S., according to the CDC. Last year's number was 34.
The current season appears to be somewhere in between a pandemic and the past two flu seasons, which were notably mild. CDC doctor Lyn Finelli settled on the word "severe" in a recent press release.
And it's been an especially severe season for seniors, she wrote. More than half of the people reportedly hospitalized for the flu this season have been ages 65 or older.
Regardless of how the numbers turn out, doctors still advise most people ages 6 months and up to get vaccinated against the flu if they haven't already.
"Because you can have a late flu season even into April or May, we don't think there's ever a time not to get (a vaccine) in the winter. You never know if there will be a peak later in the season," DeHovitz said. Officials say this year's vaccine has turned out to be well-matched to the flu strains that are circulating.
After her frightening experience, Peterson said she's become a believer in regular flu shots. She hasn't been getting them in recent years, in part because she hates needles.
"I'm going to have to get over it and just do it," she said. "Now I've changed my philosophy."
In her Stanford Medical Center office, Yvonne Maldonado was matter-of-fact as she pulled up CDC charts and maps on her computer, clicking through statistics on hospitalizations, positive influenza tests and general ILI (Influenza-Like Illness) activity across the country. She had been asked about the flu more than a few times already.
Maldonado, chief of pediatric infectious diseases, is also deeply immersed in monitoring ILI activity on the Stanford campus. She sees flu-test results from the main hospital, the children's hospital, the student health center on campus and satellite facilities.
"Over 50 to 60 percent of tests are negative for the flu," she said.
Maldonado said it's too early to give a definitive answer on how serious the current flu season will turn out but said it's unlikely to be a match for 2009. She pointed to a CDC chart marked "Laboratory-Confirmed Influenza Hospitalizations. The H1N1 year stands out as a big spike.
"That year we had the disease in late April. That (flu) season really didn't end," she said. By the time H1N1 started to taper off, a new flu season began. "When you have a new strain, that disrupts everything," she said. "It was an odd year."
Influenza comes in two major forms, A and B, with A being more serious and more common, Maldonado said. In turn, A is sorted into combinations of H and N types. Every year there are different strains and mutations, "which is why every year we need a new vaccine," she said.
The predominant strain this season is H3N2, a common one. When asked how it differs from other strains, Maldonado said that it may cause some more hospitalizations but adds that flu symptoms are pretty much the same across strains: "Flu is flu."
The important distinction to remember, she added, is the difference between the flu and a simple head cold. Influenza is not just a cough, and it's not just the sniffles. With the flu, most people have a fever, and headaches, sore throats, coughs and stuffy noses are also common. Kids sometimes have upset stomachs. Pretty much everyone gets that hit-by-a-truck feeling.
"I always tell people that flu is really overwhelming; it's not a cold. You get body aches, fever. You can't get out of bed," Maldonado said. "When you have the flu, it's a systemic illness."
It's a systemic illness that people would do well to avoid in the first place, Maldonado said. Every year, flu vaccines are ready by September, and she advises making a yearly autumn routine of getting the shot or the nasal-mist version. At Packard Children's Hospital, "we try to get all patients vaccinated before they go home," she said.
These days there are several options for getting vaccinated. There's the trusty flu shot in the arm, with lower doses for children and higher doses available for seniors. People who are leery of needles can choose a smaller microneedle.
The high-dose vaccine, which contains four times the amount of antigen, was approved at the end of 2009 by the U.S. Food and Drug Administration for people ages 65 and older.
"That's because adults over 65 tend to have a poorer response to the flu vaccine than younger adults," DeHovitz said. "When you give the higher-potency vaccine, you get their antibody levels up to a more normal level. There are a number of studies that are going on to see if this is a better vaccine. ... Right now, the CDC says either one is an option for seniors."
DeHovitz said the only side effect he's seen in the high-dose option is more arm soreness from the shot.
A nasal-mist flu vaccine has also been around for a decade, available for healthy people ages 2 to 49 who are not pregnant.
"We recommend both vaccines, but the downside of the flu mist is that because it's a live (attenuated) virus, it can cause some nasal congestion," DeHovitz said.
Overall, physicians recommend that nearly everyone ages 6 months and older get vaccinated against the flu, with a few caveats. People with fevers should wait until they get better, and those who have severe egg allergies or a history of Guillain-Barre Syndrome — or who have had a bad reaction to a flu vaccine in the past — should consult their doctors, according to the CDC.
Of course, not everyone chooses to get vaccinated, but the CDC says it's especially important for people who are at high risk for developing complications from the flu. That includes seniors, pregnant women, kids under 5 and people with medical conditions including asthma, heart disease and weakened immune systems. Since children under 6 months can't get vaccinated, it's also key for all the people around them to get a flu shot or the flu mist.
Officials emphasize that the vaccine cannot give people the flu. The unfortunate sorts who come down with the flu right after getting a shot either have a non-flu virus or have one of the strains not protected against in the vaccine — which is less likely but possible, the CDC reported. In addition, the vaccine takes two weeks to take effect, and it's possible to come down with the flu before the body has built up sufficient protection.
Because the flu has gotten press recently, DeHovitz said he's seen "definite interest" in vaccines from patients who didn't get vaccinated last fall. Some vaccine vendors in the U.S. have had shortages because of the late demand, but this doesn't seem to be endemic.
Santa Clara County seems to have experienced only occasional brief shortages, Fenstersheib said. For example, a drugstore might be out of vaccine one day and then get a new shipment the next. The Palo Alto Medical Foundation reported on Jan. 16 that it was not able to schedule new flu-vaccine appointments — but by the following week it had received more vaccine and was scheduling appointments again.
For people who choose not to get vaccinated (and indeed for everyone), Fenstersheib dispenses his typical annual advice: If you're sick, stay home from school or work and keep it to yourself. If you think you really have the flu, see your doctor. Anti-flu medications can reduce the severity of the illness if given within the first 48 hours.
And, of course, there's Public Health 101: Wash your hands frequently. Flu viruses like to pass from person to person through coughs and sneezes, and they are also fond of passing via touch. We shake hands; we pick things up; we grasp doorknobs; and we all touch our faces, even if we think we don't, Fenstersheib said.
"We could probably decrease a lot of this with a lot of hand-washing," he said. "It's just so easy and it doesn't hurt anything."
Info: Updates on the flu season from the national Centers for Disease Control and Prevention are available at www.cdc.gov/flu/weekly/fluviewinteractive.htm. Reports from the California Department of Public Health Influenza Surveillance Program are posted at www.cdph.ca.gov.