Flu activity winds down across Northern Hemisphere

Apr 27, 2012 (CIDRAP News) – The latest snapshot of the US flu season shows that significant activity is still occurring, though infection levels are declining, the US Centers for Disease Control and Prevention (CDC) said today.

The proportion of respiratory specimens testing positive for flu rose last week, from 17.5% to 22.2%, which shows that flu activity is ongoing, according to the CDC's latest update. In the late but mild flu season, activity is likely to continue for weeks to come, it said.

Overall, the share of doctor visits for flu-like illness fell from 1.5% to 1.3%, keeping it well below the national baseline of 2.4%. However, the level for the Pacific Northwest—Alaska, Idaho, Oregon, and Washington—was still above the baseline.

Deaths from pneumonia and influenza dropped again, staying below the epidemic threshold. Three more pediatric flu deaths were reported, pushing the season's total to 18. One was associated with the 2009 H1N1 virus, one involved H3N2, and the other featured an undetermined influenza A subtype.

Only four states reported that flu was geographically widespread, a decrease from six the previous week. Ten states reported regional spread.

Globally, flu activity has peaked in most temperate regions of the Northern Hemisphere, the World Health Organization (WHO) said today. Overall flu activity has decreased in the United States for 4 weeks in a row and in Canada for 3 consecutive weeks, according to the surveillance update.

The WHO noted a slight increase in the number of oseltamivir-resistant isolates  in the United States. Last week, the CDC reported six additional resistant H1N1 isolates, which pushed the resistant percentage for H1N1 to 2%. The CDC reported two more resistant H1N1 isolates this week, raising the season's total to 15.

The United States and the United Kingdom had milder flu activity this season than in past years, though other countries in Europe and northern Asia have seen levels similar to previous years, the WHO said.

Areas of the world seeing increasing flu activity include Oman (2009 H1N1) and the Dominican Republic (H3N2). Over the past few weeks, high proportions of 2009 H1N1 cases have been detected in India and Bangladesh, the WHO said.

Meanwhile, the European Centre for Disease Prevention and Control (ECDC) said today that the flu season is drawing to a close throughout Europe. Activity was stable or decreasing in all countries except for Northern Ireland. All countries are reporting low influenza intensity, except for Slovakia, which is reporting moderate intensity, the agency said.

See also:

Apr 27 CDC flu update

Apr 27 WHO influenza update

Apr 27 ECDC weekly flu overview

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