US flu markers are still climbing steadily, with the virus linked to nine more deaths in children, the US Centers for Disease Control and Prevention (CDC) said today in its weekly update.
The percentage of clinic visits for flulike illness has now been above the national baseline for 9 consecutive weeks. Last week the level rose to 5.2%, up from 4.8% reported the week before.
Respiratory specimens testing positive for flu rose from 20.9% to 24.2%, and results from CDC and clinical labs show that while most are still influenza A, the percentage of influenza B viruses found in samples rose from 12.3% to 16.7% last week. A shift toward more influenza B viruses is common for the latter part of the flu season.
H3N2 is still the dominant strain, accounting for 93.6% of subtyped influenza A samples.
The CDC's maps show that flu is geographically widespread now in 46 states and Puerto Rico, an increase of 3 states from the previous week. High-intensity flu activity, another measure of clinic visits for flu, was reported for 28 states and New York City, reflecting an increase of 5 states compared with the week before.
Hospitalizations, deaths rise
Hospitalizations for flu are also increasing steadily, with the overall rate now at 29.4 per 100,000 population, the CDC said. The highest level is still in seniors, a group known to be hit hard by the H3N2 subtype. Compared with the previous week, the rate in that group rose from 113.5 to 136.6 per 100,000 population.
The 9 new pediatric flu deaths lift the season's total to 29. Six were linked to H3N2, two were from unsubtyped influenza A viruses, and one was from influenza B. The CDC started tracking pediatric flu deaths in the 2004-05 season, and totals have ranged from a low of 37 to a high of 171.
Overall deaths from pneumonia and flu were at 7.8%, keeping the level above the epidemic threshold of 7.5% for this point in the flu season.
Flu still elevated in Europe, with some declines
In Europe, which saw an early start to a flu season that has also been dominated by H3N2, activity is still elevated, with 22 of 43 countries reporting medium to very high-intensity flu activity and 22 reporting widespread disease, according to a joint weekly update from the European Centre for Disease Prevention and Control and the World Health Organization Regional Office for Europe.
The proportion of respiratory specimens that tested positive for flu in Europe dropped slightly last week, to 42% from 45%, and officials reported another decrease in the number of new hospitalizations for flu.
Feb 17 CDC FluView update
Flu News Europe update