Avian Flu Diary: North America: Flu Activity Week 1

# 5232

The latest FluWatch and FluView numbers were released on Friday and together they describe a mixed bag of influenza activity in North America.

Unlike the UK and parts of Europe, which are still dealing with the return of the 2009 H1N1 virus – most of our identified influenza A activity stems from the recently emerged Perth A/H3N2 virus.

Starting with Canada’s weekly FluWatch report, we find that localized flu activity continues to increase across the country, and testing reveals mostly A/H3N2 and increasingly, influenza B among influenza positive samples.

January 2 to January 8, 2011 (Week 1)

The ILI consultation rate, which includes flu and non-flu respiratory complaints, is running higher than it was this time last year, but substantially below that which was seen during the height of the pandemic, and very near the mean rate of the last decade.

Moving on to the CDC’s weekly FluView surveillance report, we find that influenza activity is down a little over the previous week, although that may be due to gaps in reporting over the holidays.

2010-2011 Influenza Season Week 01 ending January 8, 2011

All data are preliminary and may change as more reports are received.

Synopsis:

During week 1 (January 2-8, 2011), influenza activity in the United States decreased in several indicators, but it is unlikely that influenza activity for this season has peaked.

Of the 4,331 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories and reported to CDC/Influenza Division, 706 (16.3%) were positive for influenza.

The proportion of deaths attributed to pneumonia and influenza (P&I) was at the epidemic threshold.

Four influenza-associated pediatric deaths were reported. Two of these deaths were associated with influenza A (H3) viruses and two were associated with influenza B virus infection.

The proportion of outpatient visits for influenza-like illness (ILI) was 2.2%, which is below the national baseline of 2.5%. One of the 10 regions (Region 4) reported ILI above region-specific baseline levels. Four states experienced high ILI activity, New York City experienced moderate ILI activity, four states experienced low ILI activity, 42 states experienced minimal ILI activity, and data were insufficient from the District of Columbia.

The geographic spread of influenza in 11 states was reported as widespread; 17 states reported regional influenza activity; the District of Columbia and 16 states reported local influenza activity; the U.S. Virgin Islands, and six states reported sporadic influenza activity, and Guam reported no influenza activity.

U.S. Virologic Surveillance:

WHO and NREVSS collaborating laboratories located in all 50 states and Washington D.C. report to CDC the number of respiratory specimens tested for influenza and the number positive by influenza type and subtype. The results of tests performed during the current week are summarized in the table below.

All 50 states and the District of Columbia have reported laboratory-confirmed influenza this season.

Pneumonia and Influenza (P&I) Mortality Surveillance

During week 1, 7.7% of all deaths reported through the 122-Cities Mortality Reporting System were due to P&I. This percentage was at the epidemic threshold of 7.7% for week 1.

As I mentioned last week, the 2011 FluView report has several new demographic charts that may be of interest to many of my readers, including this one which shows the underlying conditions most often described in hospitalized influenza cases.