Flu season shows signs of life in US, EU

Jan 27, 2012 (CIDRAP News) – Flu activity in the United States and Europe showed more signs of picking up last week, with labs in both parts of the world finding higher percentages of positives in tests of respiratory samples, according to new surveillance reports today.

In the Unites States, flu activity is still relatively low, but the Centers for Disease Control and Prevention (CDC) said it expects levels to increase over the coming weeks, according to an update today.

The percentage of respiratory specimens that were positive for flu crept a little higher, to 4.9% from 4.3% reported the week before. However, the CDC said doctor visits for flu-like illness are still below national and regional baselines.

The H3N2 virus has dominated at the national level so far, but the CDC said that for the past 3 weeks the 2009 H1N1 virus has dominated in the CDC region that includes Arkansas, Louisiana, New Mexico, Oklahoma, and Texas. Those states, however, are still seeing little overall flu activity.

Two of the states share a border with Mexico, which has reported a recent surge in 2009 H1N1 cases. Though the H3N2 virus has been predominant in most parts of the world over the past several months, Mexico is one of the few countries to report a high percentage of the former pandemic strain, which makes up 90% of the countries' recent flu detections.

No states are reporting widespread flu activity. Four (Colorado, Kentucky, Missouri, and Virginia) are reporting regional flu activity, an increase of one from the previous week.

The CDC received its first report of a pediatric flu death this season, which occurred at the end of October and involved influenza B. The percentage of overall deaths from pneumonia and flu rose above baseline last week for the first time this season.

Few viruses have been tested so far for antiviral resistance, and so far the isolates have been susceptible to the two most frequently used flu drugs, oseltamivir (Tamiflu) and zanamivir (Relenza).

Elsewhere, the European Centre for Disease Prevention and Control (ECDC) reports that flu activity is building slowly in countries scattered across the European Union (EU) in a season that so far is dominated by the H3N2 subtype.

Most countries are still reporting low flu activity, with Bulgaria, Iceland, Italy, and Spain reporting moderate levels, according to the ECDC. Nine countries reported increasing clinical activity patterns for flu since the previous week.

The percentage of respiratory specimens testing positive for flu in EU countries rose to 29.3%, an increase from the previous week and continuing an upward trend that began in December 2011.

Though most positive flu specimens in the EU have been H3N2, the ECDC said the 2009 H1N1 virus has played a role in some of the severe infections that have been reported.

The ECDC said no resistance to neuraminidase inhibitors has been detected. Global health officials have remained vigilant for any unusual increases in oseltamivir-resistant 2009 H1N1 cases in the wake of earlier reports from Australia of clusters of resistant cases in certain areas of New South Wales during the Southern Hemisphere's 2011 flu season.

See also:

Jan 27 CDC weekly flu update

Jan 27 ECDC flu update

Jan 23 CIDRAP News item on H1N1 in Mexico

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