US flu activity rises ahead of holiday season

With Christmas holiday days away, the nation's flu markers are showing spirited rises, with 29 states reporting widespread activity and the disease affecting nearly all regions, the US Centers for Disease Control and Prevention (CDC) said today.

With the H3N2 virus as the clearly dominant strain, health officials have been closely tracking a mismatch with the strain included in the vaccine, which has now risen to account for 69.4% of the circulating H3N2 viruses, up from 67.5% the week before.

The CDC said today that it expects flu activity to increase even more in the weeks ahead, and it urged people who haven't been immunized against the disease to get vaccinated now.

Flu markers show steady rise

Among other flu markers, 25.9% of respiratory specimens were positive for flu last week, increasing from 21.2% the previous week. The percentage of doctors' visits due to influenza-like illness (ILI) rose to 3.7%, putting it above the national baseline of 2.0%. Nine of the CDC's 10 regions were above their baselines for doctors' visits for ILI.

Thirteen states and Puerto Rico reported high ILI activity, another indicator of doctors' visits for the disease. Except for Minnesota, most are southern and central states.

Hospitalization rates were highest in adults age 65 and older and in children up to age 4. Nearly 95% of hospitalizations related to flu were linked to influenza A, which includes H3N2.

Four more pediatric flu deaths were reported, bringing the season's total so far to 11. Two were linked to H3N2, one was from an unsubtyped influenza A virus, and one was associated with influenza B. Overall deaths from pneumonia and flu remained below the epidemic threshold of 6.7%.

The reach of the disease also expanded dramatically last week. The CDC said 29 states and Guam reported widespread flu activity, up from 14 the week before. Except for Colorado and Texas, most of the states reporting widespread flu are in the eastern half of the United States.

Fourteen states and Puerto Rico reported regional spread, and only two—Hawaii and Oregon—reported sporadic activity.

Enough Tamiflu, but spot shortages

Rising flu activity is increasing the demand for Tamiflu (oseltamivir), and though spot shortages are being reported in some locations, Genentech, the company that markets the drug under Roche, said yesterday that it anticipates ample supply for the season.

The company said it is working with distributors and retail chains to provide consistent access to the drug. It said if necessary, pharmacies should work with authorized distributors to get additional supplies of Tamiflu capsules and oral suspension.

Genentech said that if oral suspension isn't available, pharmacists can mix 75-mg capsules into an oral suspension. The oral suspension is typically given to young children and others who have difficulty swallowing tablets.

Scattered shortages of the oral suspension have been reported in past flu seasons, including in January of this year and in 2013, 2011, and during the 2009 H1N1 pandemic, requiring pharmacies to compound it from capsules. In the past the company has said it takes significantly more resources to make the liquid suspension compared with the tablets.

Global flu patterns

Globally, the World Health Organization (WHO) said flu activity in North America has passed the seasonal threshold, with most disease linked to H3N2. Flu levels are climbing in Europe, but there is no clear indication that the region's flu season has started, the agency said in its Dec 15 report.

Other parts of the world seeing increases include eastern Asia, where H3N2 is the dominant strain; northern and western Africa, where influenza B is predominant; and some tropical areas of the Americas, such as some Caribbean countries.

See also:

Dec 19 CDC Flu View

Dec 19 CDC flu situation update

Dec 18 Genentech statement

Dec 15 WHO global flu update

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