The Center for Disease in Atlanta has reported that Influenza activity increased sharply in the last week of December. The number of jurisdictions experiencing high activity went from 21 states to 26 states and New York City, and the number of states reporting widespread activity went from 36 to 46. Influenza-like illness went from 4.9% to 5.8%. These indicators are similar to what was seen at the peak of the 2014-2015 season, which was the most severe season in recent years. Typically, severity indicators (e.g., hospitalization rates) lag behind activity indicators (ILI and geographic spread). CDC continues to recommend influenza vaccination as flu viruses are likely to continue circulating for weeks. In addition, in the context of widespread influenza activity, CDC is reminding clinicians and the public about the importance of antiviral medications for treatment of influenza in people who are severely ill and people who are at high risk of serious flu complications.
Below is a summary of the key flu indicators for the week ending December 30, 2017 (week 52):
- Influenza-like Illness Surveillance: For the week ending December 30, the proportion of people seeing their health care provider for influenza-like illness (ILI) was 5.8%, which is above the national baseline of 2.2%. All 10 regions reported a proportion of outpatient visits for ILI at or above their region-specific baseline levels. ILI has been at or above the national baseline for six weeks so far this season. During recent seasons, ILI has remained at or above baseline for 13 weeks on average.
- Influenza-like Illness State Activity Indicator Map: New York City and 26 states experienced high ILI activity (Alabama, Arizona, Arkansas, California, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Michigan, Mississippi, Missouri, Nebraska, Nevada, New Jersey, New Mexico, Ohio, Oklahoma, Oregon, South Carolina, Texas, Virginia, Washington, and West Virginia). Puerto Rico and nine states (Alaska, Colorado, Hawaii, Iowa, Massachusetts, North Carolina, Pennsylvania, Tennessee, and Wyoming) experienced moderate ILI activity. The District of Columbia and six states (Florida, Minnesota, New York, South Dakota, Utah, and Wisconsin) experienced low ILI activity. Nine states experienced minimal ILI activity (Connecticut, Delaware, Idaho, Maine, Montana, New Hampshire, North Dakota, Rhode Island, and Vermont).
- Geographic Spread of Influenza Viruses: Widespread influenza activity was reported by 46 states (Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin, and Wyoming). Regional influenza activity was reported by 4 states (Hawaii, Maine, New Hampshire, and New Jersey). Local influenza activity was reported by the District of Columbia. Guam, Puerto Rico and the U.S. Virgin Islands did not report. Geographic spread data show how many areas within a state or territory are seeing flu activity.
- Flu-Associated Hospitalizations: Since October 1, 2017, 3,927 laboratory-confirmed influenza-associated hospitalizations have been reported through the Influenza Hospitalization Network (FluSurv-NET), a population-based surveillance network for laboratory-confirmed influenza-associated hospitalizations. This translates to a cumulative overall rate of 13.7 hospitalizations per 100,000 people in the United States.
- The highest hospitalization rates are among people 65 years and older (56.6 per 100,000), followed by adults aged 50-64 years (15.4 per 100,000), and children younger than 5 years (9.9 per 100,000). During most seasons, children younger than 5 years and adults 65 years and older have the highest hospitalization rates.
- Mortality Surveillance:
- The proportion of deaths attributed to pneumonia and influenza (P&I) was 6.7% for the week ending December 16, 2017 (week 50). This percentage is below the epidemic threshold of 6.9% for week 50 in the National Center for Health Statistics (NCHS) Mortality Surveillance System.