Most measures of US influenza activity continued dropping last week, but 10 states still had widespread cases, and the death toll in children increased by nine, the Centers for Disease Control and Prevention (CDC) reported today.
In its weekly update, the CDC said 10.8% of 6,813 respiratory specimens tested positive for flu, which is down from 13.9% of 6,887 samples the week before.
The 10 states with geographically widespread activity compare with 17 states a week earlier. Most of them are in the Northeast, but they also include Arizona. Another 22 states had regional flu activity, with the rest reporting only local outbreaks or sporadic cases.
The share of medical visits for flu-like illness (ILI) dropped to 2.3% from 2.5% the week before but stayed above the national baseline of 2.0%.
A reversal for one marker
One measure actually went into reverse: Oklahoma and Hawaii reported high ILI activity, whereas no states had reported high ILI activity the previous week. On the other hand, just two states cited moderate ILI activity, versus seven states the week before. The rest had low or minimal activity.
The nine new pediatric deaths compare with just two a week earlier and raise the seasonal total to 61. Five of the deaths were associated with the 2009 H1N1 (pH1N1) virus, one involved an influenza B virus, and three involved type A viruses that were not subtyped, the CDC said.
The agency's surveillance system for flu hospitalizations, which covers about 8.5% of the US population, picked up another 333 cases last week, raising the season's total to 7,406. That signals a hospitalization rate of 27.4 per 100,000 population.
Addressing the CDC's Advisory Committee on Immunization Practices this week, CDC flu expert Lynn Finelli, MD, described this flu season as moderate and said it peaked in late December and early January.
Finelli said the proportion of outpatient visits for ILI peaked this season at 4.6%, well below last year's 6.1%. Also, the estimated flu hospitalization rate of 27.4 per 100,000 population is well below the rate at this time last year, which was 35 per 100,000.
Last season was dominated by H3N2 viruses, whereas pH1N1 is the overwhelmingly predominant strain this year.
Mixed picture in Europe
In Europe, flu activity varied last week, with some countries reporting increasing detections, while cases continued to taper off in others, according to today's update from the European Centre for Disease Prevention and Control (ECDC). Finland and Greece, for example, reported high-intensity activity. Decreasing trends for at least 3 straight weeks were reported by Bulgaria, Portugal, and Spain.
Flu activity is considered widespread in the United Kingdom and 14 other countries, including Belgium, Croatia, and France, the ECDC said.
Almost all (98%) of flu viruses were influenza A, and of those, 58% were the pH1N1 virus and 42% were H3N2. The agency said the percentage of respiratory specimens testing positive for flu decreased for the fourth consecutive week.
As for the global picture, the World Health Organization (WHO) presented a mixed pattern in an update that was dated Feb 24 but posted today.
The WHO said flu activity was declining in Canada, Mexico, and the United States but remained elevated in all three countries. Cases in Europe likewise remained high, with trends suggesting that the wave of activity is moving generally from south to north. Both influenza A viruses were circulating there, the agency said.
East Asia also has elevated flu activity, with pH1N1 predominant, the WHO said. In northern Africa and western Asia, the picture has been varied, with Egypt reporting high pH1N1 activity and an increase in severe cases.
Of flu viruses that were analyzed in 93 countries, 89% were type A and 11% were type B, the WHO reported. And among the A viruses, 77% were pH1N1 and 23% were H3N2.
Staff writer Lisa Schnirring contributed to this story.
See also:
CDC FluView report
Feb 28 ECDC weekly flu update
Feb 24 WHO flu update
