"My message today is that this is influenza, it is not super-influenza," Schwarz said at a news conference Friday. It does not seem to severely affect children, he said. "The only surprising thing is how early it happened this year."
It is that timing that many physicians and emergency department directors believe is responsible for what nearly all agree has been an unusually large number of patients seeking treatment for respiratory infections since early December.
Basically, the early flu arrived in the middle of the typical season for a range of other infections, from rhinovirus to RSV, that in most years have already peaked by the time influenza shows up. Those other viruses are worst in children, and pediatric emergency rooms have been at near-record levels for weeks.
"I think of the flu as being high fever, sick as a dog, coughing, not wanting to get out of bed, just really weak," said Charles A. Scott, a pediatrician with offices in Medford and Mansfield, Burlington County. "There's another virus out there that is causing all the above except for the high fever."
Plus, there's norovirus - a nasty but short-lived gastrointestinal bug that is often called stomach flu but is unrelated to influenza, said Russell Breish, a family physician at Chestnut Hill Hospital who also works in a nursing home. Norovirus is cyclical, typically coming every few years, often in late January.
It is so contagious, and the bouts of vomiting and diarrhea that can cause dehydration are so dangerous to the elderly, that a single case in a nursing home is cause for alarm, and a cluster may lead to a lockdown.
Norovirus arrived earlier and with more severity than last season, the city Department of Public Health said in an advisory Tuesday. There have been six outbreaks so far.
There also have been seven influenza outbreaks in long-term care facilities in the city, and 72 statewide. New Jersey reported 27 in such facilities.
Some pediatricians said they were seeing somewhat more serious disease than normal. And while many did not, the Centers for Disease Control and Prevention has been taking the flu very seriously for weeks, in part based on historical patterns.
The type of flu that has dominated the season here and in much of the country, known as H3N2, typically causes more severe illness than other types and is particularly dangerous for the elderly - quite different from the pandemic H1N1 three years ago, against which elderly people seemed to have the most immunity.
This season is sometimes compared with 2003-04, when the flu arrived even earlier. It was also dominated by H3N2 and ended up being a bad one. Indeed, the CDC's concerns, which led to a strong push for vaccination especially this year, may have contributed to spot shortages of vaccine despite the distribution of 128 million doses so far.
On Friday, the agency released data showing that this year's vaccine was roughly 62 percent effective. "If you get the flu vaccine, you are 62 percent less likely to have to go to your doctor to be treated for flu," CDC director Thomas Frieden told reporters during a teleconference. Vaccinated people who get the flu may also have a less-severe illness.
Although the flu has begun to decline in some parts of the country - it began, as usual, in the South, and may be waning there - Frieden emphasized the virus' notorious unpredictability in urging people to still be immunized.
The recent holiday season makes predictions harder, because the interruption in work and school can lead to a drop that is temporary.
In the Philadelphia region, emergency room overcrowding eased over Christmas but has picked up. There also has been significant variation locally.
Temple University Hospital has "not seen anything out of the ordinary, except for the fact that the number of cases we are seeing is more typical for later in January or February," a spokesman said.
In Darby Borough, less than 15 miles away, Mercy Fitzgerald Hospital "has been seeing its highest volume in a 10-day period ever," a spokeswoman said Friday.
While Schwarz sought to assuage fears of a super-influenza, he, too, emphasized the unpredictability and normal seriousness of the disease. Nevertheless, he predicted that flu in the region was near its peak and would continue for four or five weeks.
"One, get a flu shot. Two, get a flu shot." (City clinics have plenty of vaccine.) "Three, if you are sick, avoid close contact with other people. Four, wash your hands." And five, "good nose-mouth care" - in other words, don't touch your nose or mouth and then shake hands.
Contact Don Sapatkin at 215-854-2617 or firstname.lastname@example.org.