Flu situation stays sedate, locally and globally

May 20, 2011 (CIDRAP News) – Flu indicators fell again in the United States last week as the 2010-11 flu season approaches its end, with very little activity occurring elsewhere in the world, US and global surveillance organizations said today.

All levels were below baseline, even the percentage of deaths from pneumonia and flu, which has lagged the decline of other flu signals, the US Centers for Disease Control and Prevention (CDC) said today.

Visits to the doctor for flu-like illness decreased again for the 12th week in a row, keeping at a summertime level.

No states reported widespread, regional, or local flu activity. Puerto Rico and 27 states reported only sporadic activity, the CDC said.

Three pediatric flu deaths were reported, raising the season's total to 105. One was from the 2009 H1N1 virus, one was from H3N2, and one was from an unsubtyped influenza A virus.

Influenza B was the dominant strain, followed by H3N2, unsubtyped influenza A, and 2009 H1N1, according to the CDC.

Routine surveillance for oseltamivir (Tamiflu)-resistant 2009 H1N1 viruses found one more isolate, pushing the season's total to 40.

In global flu developments, a few tropical countries are reporting low-grade transmission, including the Dominican Republic, Venezuela, Jamaica, Rwanda, and Madagascar, the World Health Organization (WHO) said today. The predominant viruses in those locations vary and range from 2009 H1N1 in the Dominican Republic to influenza B in Madagascar.

In Venezuela, an earlier surge in 2009 H1N1 activity that peaked in late March has now subsided to very low levels. Several countries in Central and South America are reporting increases in respiratory infections due to respiratory syncytial virus (RSV).

Only small numbers of viruses have recently been detected in Europe, North Africa, and the Middle East. Of the few detected, influenza B has been most common. Likewise, in eastern Asian countries such as China and Japan flu levels are very low, with influenza B as the most commonly detected strain, the WHO reported.

So far the surveillance findings don't suggest that flu season has started yet in the Southern Hemisphere's temperate countries, where the season typically runs from May through October. Australia had previously reported higher-than-expected numbers of flu detections in two northern states, but detections have decreased in most areas in recent weeks, the WHO noted. Over the Southern Hemisphere's summer the country reported low-level but persistent H3N2 circulation, but over the past week 2009 H1N1 and influenza B strains have been more frequently detected.

See also:

May 20 WHO flu update

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