Influenza Surveillance Update – Alicia Budd (CDC)
Alicia provided an update for influenza activity through Week 21, ending May 23, 2020. She pointed out that CDC has now transitioned to the more abbreviated “summer version” of the FluView report, where CDC reports on only a few key highlights. However, CDC continues to run most of the surveillance components thoughout the year. If anything unusual is seen, information will be added to this brief report.
Alicia called attention to CDC’s weekly COVIDView surveillance summary, which will continue to be issued each week throughout the summer. This includes many of the same systems highlighted in FluView, as well as a few additional reports specific to COVID-19. She emphasized that COVIDView is not meant to be an all-inclusive source of COVID information. The remainder of Alicia’s presentation included information gleaned from both FluView and COVIDView.
Influenza activity continues to remain very low at the current time. In general, on a national basis, SARS-CoV-2 also appears to be declining overall, although levels remain high and hot spots are in evidence. Flu virus activity has been very low for several weeks. Although testing volume is relatively low, this does not appear to be impacting our numbers; rather, there truly appears to be a low level of flu activity. The majority of this low number of positives appears to be H1N1, with a small amount of influenza B.
CDC has reported (in COVIDView) molecular testing results from public health labs, some commercial labs, and a subset of clinical labs. This data is not meant to cover every test conducted in the U.S. It uses a combination of CDC’s regular reporting mechanisms for virologic surveillance and some additional lab data that CDC does not typically get during a flu season. These data indicate that, overall, the percent of specimens testing positive for SARS-CoV-2 has declined nationally. On a regional level, the Southeast and Pacific Northwest regions saw a slight increase in percent positives. CDC will continue to monitor this closely.
In terms of sheer numbers, COVID is not affecting children as greatly as adults. Less than 5% of the specimens CDC has tested are from children. Within this small group, however, the positives have either trended up or remained relatively stable in the 0–4 and 5–17 year age groups. This differs from adult testing, where the percent positivity has been seeing steady declines. It is challenging to interpret this data due to continuing fluctuations in who is being tested.
Reported influenza-like illness (ILI) has been below baseline levels for several weeks at both the national and regional levels. COVID also uses data from the ILI system, as well as data from the National Syndromic Surveillance Program (NSSP), which monitors emergency department visits for ILI and COVID-like illness. ILI is a relatively good marker for COVID because it is looking for general respiratory illness, and mild to moderate COVID illness often presents with symptoms similar to ILI. Both ILI and NSSP data appear to be showing decreasing levels of COVID-like illness as well.
Lab-confirmed hospitalization data for both pneumonia and influenza (P&I) and COVID is captured in specific sites across the country. The FluSurvNet system has been stopped for this season. Our overall cumulative rate for the 2019–2020 influenza season for all ages combined was 69/100,000. This is higher than several recent flu seasons. The relative impact varied greatly by age group, with higher than ever previously experienced rates for the 0–4 and 18–49 year age groups. Rates for the 5–17 year age group also were higher than any other recent season, but lower than the 2009 pandemic levels. The rates for all adults >50 years were within the range seen during recent flu seasons. The overall cumulative rate for COVID hospitalizations from March 1 – May 21 was just over 73/100,000. These rates are generally higher in older adults >65, followed by persons 50–64 years. The cumulative COVID hospitalization rates for persons 18–49 and 50–64 years are already higher than the cumulative end of season flu hospitalization rates seen during each of the last 5 seasons. For those >65 years, hospitalization rates are generally similar for both COVID and influenza, while hospitalization rates for children are much lower for COVID than for flu.
The COVIDView report now includes information on the differential impact of infection by race and ethnicity. Rates were adjusted to account for differences in age distribution within the race and ethnic strata in each of the catchment areas. Compared with non-Hispanic whites, the non-Hispanic black and non-Hispanic American Indian/Alaska Native populations had rates that were ~4.5 times higher, while Hispanic and Latino populations had rates ~3 times higher. These data will continue to be included in future COVIDView reports.
A total of 179 influenza-associated pediatric deaths have been reported to date for the 2019–2020 influenza season. The most recent report occurred in May and was due to influenza A virus infection. Overall, approximately 60% of the reported pediatric cases have been due to influenza B, and all of these with lineage testing conducted were B Victoria. Of the influenza A cases for which subtyping was conducted, all but one were determined to be influenza A (H1N1).
Influenza mortality is determined through looking at the percent of deaths reported to be due to pneumonia and influenza (P&I) and comparing that to the epidemic threshold. When the percent is above the epidemic threshold, it indicates that the observed proportion of deaths is significantly higher than would be expected at that time of year in the absence of substantial flu activity. Similarly, COVID mortality is determined by looking at death certificates listing COVID, pneumonia, or influenza as a cause of death and comparing this to the existing P&I baseline. This allows CDC to control for the seasonality of pneumonia. Pneumonia and influenza (P&I) accounted for 6.6% of deaths during the week ending May 23, which is higher than the epidemic threshold of 6.4%. When COVID reports are added to the total, the resulting pneumonia/influenza/COVID (PIC) rate was 6.8%. Both the P&I and PIC rates were above the epidemic threshold, but the PIC rate was considerably higher. Both the P&I and PIC systems have been reporting continuous declines since the very high peaks observed in mid-April, when P&I rates during week 15 were almost 16% and PIC rates in week 16 were ~28%. CDC will continue to closely monitor these reports.
In response to a question, Alicia agreed that masking, social distancing, and hand hygiene put in place for COVID contributed to the sharp decline in flu activity. However, we also need to consider the possibility that the onset of COVID “took over” respiratory virus activity. Similar results have been seen during prior flu pandemics, when a pandemic strain appeared and other strains quickly went away. At this point, it is not possible to conjecture what the impact might be with influenza and COVID co-existing in the fall. Alicia also reported that, similar to what has been seen in the U.S., countries throughout the world have seen a marked reduction in influenza activity.
Announcements – L.J Tan (IAC)
Summit Virtual Meetings –
During May the Summit held two virtual meetings:
- Developing COVID-19 Vaccines in Record Time (May 12)
- Influenza Prevention in the Era of COVID-19 (May 21)
Recordings and slide presentations from both meetings are now available online:
Summit 2020 Immunization Excellence Awards
Each year the Summit sponsors the Immunization Excellence Awards to recognize the extraordinary contributions of individuals and organizations towards improved vaccination rates within their communities during the past year. This year’s award recipients will be recognized during the virtual 2020 Immunization Excellence Awards Ceremony being held on June 18, 2020 at 3 p.m. ET. L.J encouraged Summit members to register now so that they can participate in this special event honoring this year’s awardees. He also recognized and thanked Mitch Rothholz for his multi-year leadership in coordinating the Awards.
Summit Call Schedule
L.J announced that next week’s Summit call scheduled for June 11 will be cancelled. In addition, the Immunization Excellence Awards ceremony will be held in lieu of the scheduled June 18 meeting.