"Until the first or second week of December, we were not detecting any cases here," Pegues said. During the third week, however, about 10 patients tested positive, including one transferred from another hospital.
Nationwide, there has been an uptick of about 2 percent in visits to doctors, which likely indicates that the threshold has been crossed, he said.
State records show 38 cases in Philadelphia, 50 in Montgomery County, 47 in Delaware County, 18 in Chester County, and 14 in Bucks County. But since health statistics reflect only the number of cases that have been confirmed with lab tests identifying one of the flu strains, the actual figures are undoubtedly higher, said a representative for the Pennsylvania Department of Health. Many people simply tough it out without seeking professional help.
The flu has hit the northeast corner of New Jersey, but the disease has been rare so far in South Jersey, according to a state Department of Health website.
Unlike the common cold, which creeps up slowly on its victims, the flu strikes quickly and with a vengeance. The symptoms - achy joints, fever, sore throat, cough - can evolve into a much more serious illness, especially for the young, the elderly, the pregnant, asthmatics, and those with impaired immune systems.
Understanding the potential for the flu's grave complications, public health officials are again urging everyone over age 6 months to take advantage of one of a variety of flu vaccines.
"Since we are at the very beginning of the season, it is not at all too late to get vaccinated," Pegues said. The vaccine normally requires two weeks to produce optimal immunity, but in heavily populated areas like the Philadelphia region, the flu takes a full six to eight weeks to finish its dastardly run.
The most common vaccine, which protects against the H1N1 virus, two strains of influenza A, and one of influenza B, is widely available from primary-care physicians and most large drugstore chains.
Another, inhaled through the nose, is often offered to children at their pediatrician's office. Needle-averse adults up to age 50 may also take advantage of the nasal route, Pegues said.
An egg-free vaccine has also been produced for people with egg allergies. In most flu vaccines, eggs are used as the medium for growing the virus. (Later on in the manufacturing process, the virus is killed either completely or partially.) And finally, there is a new quadrivalent vaccine - which protects against an additional strain of influenza B.
Skeptics might want to read the recent report in the Journal of the American Medical Association that found that flu shots may lower the risk of serious heart problems. In a study of 3,231 patients, participants who received the vaccine were 55 percent less likely than the placebo group to suffer major heart events. (Romantic disasters not included.)
After the 2009 pandemic, which resulted in an estimated 12,470 deaths, according to the Centers for Disease Control, all subsequent vaccines have protected against the H1N1 virus.
"It looks like, so far, indicators are projecting for a pretty typical flu season," Pegues said. "There appears to be a good match between the influenza vaccine and the circulating viruses."
Six Options for the Flu Vaccine
Regular flu shot. This "trivalent" vaccine works against the three strains of flu expected to be most common and is recommended for everyone over the age of 6 months.
Quadrivalent flu shot. This one protects against the same three strains (an A/H1N1, A/H3N2, and a Type B) plus a fourth (another B). It is recommended for everyone over the age of 6 months. This is the only shot that protects against four strains. There also is a quadrivalent nasal spray vaccine, the only nasal version this year. It is recommended for people ages 2-49 - a smaller range than the shot - who are healthy and do not want to be stuck with a needle.
High-dose flu shot. This contains a higher amount of the antigen (immune system stimulant) needed to create immunity. It is recommended for adults over 65 because the immune system weakens with age.
Intradermal (inside the skin) flu shot. This vaccine creates the same immune response but uses a much smaller needle.
Flublok flu shot. This is created without using chicken eggs and is suitable for adults ages 18-49 who are allergic to eggs. It protects against three types of flu.
Flucelvax flu shot. This vaccine is made using cultured animal cells, so it, too, is appropriate for people with egg allergies. If there is ever a flu pandemic, using cell cultures will allow vaccines to be made more quickly.
- Teagan Keating, writing on the Public's Health blog on Philly.com and Inquirer.com