Influenza Update Week Ending 2-17-2018Jenny Abercrombie
Influenza (FLU) Update for Week #7 Week Ending 2-17-18 The CDC reported that although there were multiple indicators suggesting that the flu season has hopefully peaked, flu activity is still widespread throughout the United States and, ILI, although lower, remains higher than the peaks of ILI activity in previous flu seasons. Diagnosed flu cases have also decreased slightly. Hospitalizations for this flu season are still outpacing those of the 2014-15 flu season which was considered highly severe and was also dominated by Influenza A H3N2. The good news was that the proportion of Influenza B and H1N1 cases have increased and H3N2 has decreased. Therefore, flu vaccination will likely be more effective and less people will get sick and/or cause the flu to spread. Flu activity is expected to remain elevated for the next several weeks but will likely continue to slowly taper off until falling below the expected national baseline. Although uncommon, flu seasons have been noted to have a double peak before the final return to baseline.
A quick glance at the graphs for Percentage of Visits for ILI and Pneumonia and Influenza Mortality Surveillance, gives a pictorial presentation of the severity of this flu season.
FirstWatch RIN (Regional Influenza Network) Alerts showed a slight decrease in occurrence, which seemed to correlate with the CDC reports.
For the most recently reported week ending February 17, 2018, the CDC reported:
–ILI visits to clinics & other non-hospital facilities remained elevated at 6.4% (was 7.5% last week) and at or above the national baseline of 2.2% for the 13th week in a row. All 10 regions reported ILI at or above their region-specific baselines again with 49 of 54 jurisdictions reporting ELEVATED. On average for the past five flu seasons, the ILI has remained at/above baseline for 16 weeks, suggesting elevated activity will extend well into March.
–Flu cases (documented by positive flu tests) remained elevated with widespread flu reported in 48 states. Clinical lab testing for influenza was positive for flu in 25.4% of the total tests (compared with 26.5% last week), which is another decrease. This seems to be the trend.
–Influenza A remained the dominant flu type for 58.2% of the flu tests reported (63.6% last week), with the subtype H3N2 73.7% of the time (78.4% last week), and 22.5% (18.7% last week) as A (H1N1)pdm09 viruses for the remainder. The rest of the tests showed 41.8% (36.4% last week) tested as Influenza B viruses. This is another decrease in H3N2 cases and an increase in both H1N1 and Influenza B cases. Influenza B cases usually cause a less severe flu and occur more in the latter part of the flu season.
–Vaccine Coverage: the majority of the flu viruses collected this season are well matched to the seasonal vaccine offered, although less so with the still slightly dominating H3N2, the remaining H1N1 and the B flus have a better response. Overall, vaccine effectiveness is still less than hoped for but it appears that the flu vaccine decreased the likelihood of seeing a health care practitioner because of flu, 36% this season, with the percentage increasing as H1N1 and Influenza B flus hopefully dominate. It is still recommended that anyone who has not received flu vaccine get it ASAP, since even if it doesn’t prevent the flu in everyone, the length and severity of the flu would likely be lessened as well as the time when a person is able to infect someone else (called shedding).
The CDC provides an interactive U.S. map that will link to each state’s public health authorities, ILI and Flu information and processes, as well as other diseases and public health topics. This site includes a tremendous amount of information at the State, and even Local, level.
Find it at this site: https://www.cdc.gov/flu/weekly/usmap.htm
–For Influenza-Like Illness (ILI)
High ILI Activity: (New York City, Washington, DC, Puerto Rico, and 39 states): Alabama, Alaska, Arizona, Arkansas, California, Colorado, Delaware, Georgia, Illinois, Indiana, Kansas, Kentucky, Louisiana, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Vermont, Virginia, West Virginia, and Wyoming
Moderate ILI Activity (5 states): Connecticut, Hawaii, Iowa, Utah and Wisconsin
Low Activity (3 states): Florida, Idaho and Washington
Minimal Activity (3 states): Maine, Montana and North Dakota
–For Flu (positive flu tests)
Widespread Activity: (Puerto Rico and 48 states): Alabama, Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Delaware, Florida, Georgia, Idaho, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Hampshire, New Jersey, New Mexico, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Utah, Vermont, Virginia, Washington, West Virginia, Wisconsin and Wyoming
Local Activity (Washington DC, Guam and 2 states): Hawaii and Oregon
No Activity: U.S. Virgin Islands
Hospitalizations from Flu since Oct. 1, 2017 have had a cumulative rate of 74.5 per 100,000 population. The cumulative and each age group reported significantly higher rates than those of the previous week and were again higher than the rates at the same point in the 2014-15 flu season. Specifically, those 65 years & older with 322.7/100,000; ages 50-64 at 79.9/100,000; and ages 0-4 at 47.1/100,000.
Death rates for pneumonia and influenza in adults decreased slightly again to 9.5% (9.8% last week) but remained above the epidemic threshold of 7.4%. Note: death reports often aren’t submitted for data purposes in the same time frame as Flu and ILI cases are, so they lag behind most other Flu reporting. These numbers are from week #3, ending Feb 3rd.
There were 13 more pediatric deaths from flu reported for week #7, for a total of 97 for this flu season.
–Flu in Canada and Europe:
According to the Public Health Agency of Canada (PHAC) for Week #7 (ending 2/17/18), flu activity remained peaked when looked at nationally and, although decreasing in some areas, the decline has been slow. The total number of influenza cases were about the same as those from Influenza B viruses. Most of the diagnosed flu cases, hospitalizations, and deaths remained in those 65 years and older.
For more information see: https://www.canada.ca/en/public-health/services/diseases/flu-influenza.html
According to the European Center for Disease Prevention & Control (ECDC), flu was widespread in the majority of the reporting countries for Week #7 (ending 2/18/19). Influenza A and B viruses were co-circulating with more B than A noted. Different proportions of circulating flu viruses were found among countries. For those being tested with ILI or ARI (acute respiratory infections) at PCPs, 51% tested positive for flu.
For more information see: http://www.flunewseurope.org/
See this link for more details, including charts, graphs and maps. https://www.cdc.gov/flu/weekly/