Flu Widespread in the U.S. Says CDC Report

Flu widespread in the United States, according to this week’s FluView report.  Flu activity in the U.S. continues to increase. Twenty-five states are now reporting widespread levels of activity. Additional increases across the country are expected in the coming weeks. Anyone aged 6 months and older who has not gotten a flu vaccine yet this season should get one now. Below is a summary of the key indicators for the week of December 22-28, 2013:

• For the week of December 22-28, the proportion of people seeing their health care provider for influenza-like illness (ILI) increased significantly, and is above the national baseline for the fifth consecutive week. All ten regions reported ILI activity at or above their region-specific baseline level.
• Twenty states experienced high ILI activity. This is an increase, up from six states that reported high ILI activity last week. Eight states and New York City experienced moderate ILI activity. Six states experienced low ILI activity. Sixteen states experienced minimal ILI activity. The District of Columbia did not have sufficient data to calculate an activity level.  ILI activity data indicate the amount of flu-like illness that is occurring in each state.
• Twenty-five states reported widespread geographic influenza activity, an increase from ten states in the previous week. Twenty states reported regional activity. Puerto Rico and three states reported local activity. The District of Columbia and two states (Hawaii and Rhode Island) reported sporadic influenza activity. The U.S. Virgin Islands and Guam did not report. Geographic spread data show how many areas within a state or territory are seeing flu activity.
• 1,583 laboratory-confirmed influenza-associated hospitalizations have been reported since October 1, 2013. This translates to a cumulative rate of 5.8 hospitalizations per 100,000 people in the United States.
  • Hospitalization data are collected from 13 states and represent approximately 8.5% of the total U.S. population. The number of hospitalizations reported does not reflect the actual total number of influenza-associated hospitalizations in the United States.
• The proportion of deaths attributed to pneumonia and influenza (P&I) based on the 122 Cities Mortality Reporting System decreased this week, and remains below the epidemic threshold.
• Two influenza-associated pediatric deaths were reported to CDC during the week of December 22-28. One of the deaths was associated with a 2009 H1N1 virus. The other death was associated with an influenza A virus for which the subtype was not determined. A total of six influenza-associated pediatric deaths have been reported for the 2013-2014 season at this time.
• Nationally, the percentage of respiratory specimens testing positive for influenza viruses in the United States during the week of December 22-28 increased again this week to 26.7%. During the last three weeks, the regional percentage of respiratory specimens testing positive for influenza viruses ranged from 11% to 34.9%.
• Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all been identified in the U.S. this season. To date, influenza A (H1N1) viruses have predominated. During the week of December 22-28, 1,667 of the 1,711 influenza-positive tests reported to CDC were influenza A viruses and 44 were influenza B viruses. Of the 922 influenza A viruses that were subtyped, 0.8% were H3 viruses and 99.2% were 2009 H1N1 viruses.
• CDC has antigenically characterized 452 influenza viruses, including 398 2009 H1N1 viruses, 46 influenza A (H3N2) viruses, and 8 influenza B viruses, collected since October 1, 2013.
  • All 398 of the 2009 H1N1 viruses tested were characterized as A/California/7/2009-like. This is the influenza A (H1N1) component of the Northern Hemisphere quadrivalent and trivalent vaccines for the 2013-2014 season.
  • All 46 of the influenza A (H3N2) viruses tested were characterized as Texas/50/2012-like. This is the influenza A (H3N2) component of the Northern Hemisphere quadrivalent and trivalent vaccines for the 2013-2014 season.
  • Three of the eight influenza B viruses tested belonged to the B/Yamagata lineage of viruses, and were characterized as B/Massachusetts/02/2012-like. This is an influenza B component for the 2013-2014 Northern Hemisphere quadrivalent and trivalent influenza vaccines.
  • The five other influenza B viruses belonged to the B/Victoria lineage of viruses, and were characterized as B/Brisbane/60/2008-like. This is the recommended influenza B component of the 2013-2014 Northern Hemisphere quadrivalent influenza vaccine.
• Since October 1, 2013, CDC has tested 910 2009 H1N1, 66 influenza A (H3N2), and 15 influenza B virus samples for resistance to the neuraminidase inhibitors. Oseltamvir and zanamivir are the recommended influenza antiviral drugs this season. While the vast majority of the viruses that have been tested are sensitive to oseltamivir and zanamivir, so far this season 10 (1.1%) 2009 H1N1 viruses have shown resistance to oseltamivir. No viruses have shown resistance to zanamivir.
  • As in recent past seasons, high levels of resistance to the adamantanes (amantadine and rimantadine) continue to persist among 2009 H1N1 and influenza A (H3N2) viruses. Adamantanes are not effective against influenza B viruses. Adamantanes are not recommended for use against influenza this season.