CDC: Flu continues steady retreat

Apr 15, 2011 (CIDRAP News) – Flu activity across the United States continued to show signs of slowing, the Centers for Disease Control and Prevention (CDC) said today.

For the eighth week in a row, the percentage of doctor's visits for flu-like illness dropped, falling to 1.4% from 1.6% the previous week, the CDC reported in its weekly update. All 10 of the CDC's regions stayed below their baseline flu-visit levels.

The CDC has said the flu season typically begins as early as October and lasts as late as May.

Only two states—Maine and New York—are still reporting widespread activity, which is one fewer than the previous week. Nine states reported regional activity.

The number of respiratory specimens that were positive for flu also continued to level off, decreasing from about 11% to 9.1% last week. The pattern of circulating flu strains held fairly steady, though the percentage that were influenza B rose from 31.8% to 37.5% last week. The CDC has said that all influenza types and subtypes have circulated at high levels this season, with the predominant strain varying from week to week and even region to region.

The CDC received one report last week of a pediatric flu death, which was linked to influenza B. A child flu death reported during week 12 was reclassified as due to another cause, so the number of pediatric flu fatalities held at 91 last week.

Meanwhile, the overall percentage of deaths from pneumonia and influenza stayed at 8%, keeping it above the epidemic threshold for the 11th week in a row.

Antiviral resistance testing found two more isolates that were resistant to oseltamivir (Tamiflu), an H3N2 and a 2009 H1N1 virus, bringing the season's totals to 2 and 18, respectively.

The CDC also issued an international flu update today, which reports that in Canada, influenza B detections are increasing in all but the Atlantic provinces, despite overall flu levels that are declining.

In Europe, flu levels were low except for in five countries that reported medium-intensity activity: Armenia, Iceland, Poland, Sweden, and Russia.

A report today from the World Health Organization (WHO) European Region office said the 2009 H1N1 virus isn't the dominant strain in any of the countries, though it is co-circulating with influenza B in six of them. In a nutshell, the WHO said clinical and virological signs continue to show a continuing drop in flu activity across the region.

The CDC reported that African and Middle Eastern countries are seeing an overall drop in flu activity, with the 2009 H1N1 virus overtaking influenza B as the dominant strain.

Flu activity was also low in tropical regions, with the exception of sustained circulation in sub-Saharan Africa, with increasing levels in Madagascar.

In the Southern Hemisphere, which is approaching the start of its season, flu activity is still low, the CDC reported.

See also:

Apr 15 CDC flu update

Apr 15 CDC international flu update

Apr 15 WHO European region flu report

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