KEYSTONE, COLO. — Where has all the seasonal influenza gone?
That's one of the questions preoccupying flu watchers during this unprecedented 2009-2010 influenza season. Another is: Will we see a third wave of the 2009 H1N1 influenza pandemic?
Seasonal flu in the United States ordinarily follows a predictable pattern. It arrives in force in January, peaks in February, and then tails off in March. This year, seasonal flu did not show up anywhere in the United States in January, aside from a few sporadic cases of no epidemiologic significance, Dr. Gwen Huitt said at a meeting on allergy and respiratory disease.
Instead, the Centers for Disease Control and Prevention's Outpatient Influenza-Like Illness Surveillance Network reported a huge peak in October, 4 months earlier than usual, that was the crest of the second wave of the H1N1 pandemic. The first wave came in June 2009.
“That was a paradigm shift. It was far different than anything seen in recent history,” recalled Dr. Huitt of the department of medicine at the University of Colorado, who is also an infectious disease specialist at National Jewish Health, both in Denver.
“We're treading uncharted territory right now, but the thing we're all concerned about is whether or not we'll have a third wave. The 1918 Spanish flu H1N1 pandemic had three waves. The second was the worst, and the third was almost as bad. So we're just waiting to see what happens,” Dr. Huitt said at the meeting sponsored by National Jewish Health.
The CDC has reported 59 documented cases of oseltamivir (Tamiflu)-resistant H1N1 through January of this year. A third wave of the pandemic could turn oseltamivir resistance into a major problem. Availability of another oral drug in addition to oseltamivir and zanamivir (Relenza) would be most welcome. Unfortunately, the only anti-influenza drug in phase III testing is intravenous peramivir, although it does look promising.
Seasonal influenza A isn't being seen on a significant scale anywhere in the world right now. However, an upsurge in seasonal influenza B is underway in China.
“Fortunately, it's a strain included in our seasonal influenza vaccine, so I think our population should be fairly well covered if that virus starts appearing in North America,” she said.
Disclosures: None reported.
'That was a paradigm shift. It was far different than anything seen in recent history.'
Source DR. HUITT