US influenza activity kept climbing last week, as several states outside the South reported widespread cases, and the 2009 H1N1 virus continued to be the predominant strain, according to the US Centers for Disease Control and Prevention (CDC).
Ten states reported geographically widespread flu activity, up from just four southern states the week before. The ten are Alabama, Alaska, Kansas, Louisiana, Massachusetts, New York, Pennsylvania, Texas, Virginia, and Wyoming.
Also, six states reported high influenza-like illness (ILI) activity as measured by visits to sentinel clinics, up from four states the previous week, the CDC reported. Nationally, 3.0% of medical visits were due to ILI, compared with the national baseline of 2.0%.
States with high ILI activity were Alabama, Louisiana, Mississippi, Missouri, Oklahoma, and Texas. Another eight states cited moderate ILI activity, and the rest had low or minimal numbers.
The CDC also reported a big jump in the percentage of respiratory samples that tested positive for flu: 24.1% (of 6,813 specimens), versus 17.8% a week earlier.
An H1N1 season so far
Of the positive specimens, more than 98% were influenza A viruses, and 2009 H1N1—the former pandemic virus, now a seasonal strain—accounted for nearly all of those that were subtyped. Only 1.8% of the positive specimens were influenza B isolates.
Last week the 2009 H1N1 virus was blamed for 2 of 8 severe respiratory illnesses, with 4 deaths, in the Montgomery County Hospital District near Houston, Tex. The patients were reported to be previously healthy middle-aged adults. The cluster came amid a sharp increase in flu activity in Texas.
A CDC official said last week (as reported here previously) that the 2009 H1N1 virus has a greater impact on younger adults and older children than seasonal flu strains typically do. The virus is included in this year's flu vaccine, which the official said should limit the effects on those groups if the strain continues to be dominant this season.
One pediatric flu-related death was reported last week, but it occurred during the 2012-13 season, the CDC said.
Concern about Tamiflu supply
In a related development, a television station in Little Rock, Ark., yesterday reported a local shortage of oseltamivir (Tamiflu), the most widely used flu drug, but it was not clear if there were shortages anywhere else. The station, KTHV, quoted a local pharmacist as saying he couldn't obtain the Tamiflu formulation for adults.
Tara Iannucillo, a spokeswoman for Genentech, Tamiflu's manufacturer, told CIDRAP News today that there is a sufficient supply of the drug in 75-milligram capsules.
"We have limited information regarding geographic shortages," Iannucillo commented by e-mail, adding, "We are working closely with our distributors to get Tamiflu into the areas that need it most."
She also said that if Tamiflu Oral Suspension (a liquid formulation intended for children or adults who have trouble swallowing capsules) is unavailable at a local pharmacy, patients should consult with their physician or pharmacist for additional options. Pharmacists can mix 75-mg capsules into an oral suspension for those who need it, she explained.
At the CDC, spokeswoman Erin Burns told CIDRAP News, "We have not heard of shortages of influenza antiviral drugs from manufacturers at this time. We checked in with [the Food and Drug Administration] before Christmas and they had not heard of any local, regional or national shortage issues either."
"Because it's early in the season, it's possible that some pharmacies may just be receiving their inventories at this time," Burns added. "It's also possible that in places with elevated influenza activity, locating influenza antiviral drugs may be more difficult. Patients who have been prescribed an influenza antiviral drug by their health care provider may need to call more than one pharmacy to fill their prescription."
Low activity outside North America
As for the global flu picture, the World Health Organization (WHO) reported that the flu season has begun in North America but that flu activity remained low in the rest of the Northern Hemisphere as well as in the Southern Hemisphere. The WHO update is dated Dec 20 but apparently was posted today.
From Nov 24 to Dec 7, national flu labs in 89 countries and territories tested 42,360 respiratory specimens and found that 3,304 were positive for flu, the WHO reported. Of the positive samples, 85.3% were influenza A and 14.7% were influenza B. About two-thirds of the type A viruses were 2009 H1N1 and the rest were H3N2, the WHO said.
Because of the holidays, no flu activity updates were posted this week by the Public Health Agency of Canada or the European Centre for Disease Prevention and Control.
Current CDC FluView report
Dec 20 WHO flu surveillance update
Dec 26 KTHV report
Related Dec 20 CIDRAP News story