Thread by @kerpen

Friday Fluday Thread: MMWR Week 14, ending April 10, 2021

United States Influenza testing, MMWR week 14.

CDC flu view. cdc.gov/flu/weekly/ind…

2016 to 2019 4-year average: 3,407 cases; 15.4% positive
2020: 215; 0.95%
2021: 15; 0.05%

docs.google.com/spreadsheets/d…

United States Influenza testing, season to date (28 weeks, MMWR 40 to 14)

Five-year average: 197,308 cases; 18.80% positive

Last year: 291,269; 21.02%

This year: 1,965; 0.15%

Season-to-date U. S. flu hospitalizations down 98.9% from last year.

Flu hospitalizations total (28 weeks) in FluSurv-NET catchment is 220 (+5 from last week). Through week 14 last year (27 weeks) it was 19,802 (+89)

Rate last year: 68.2 per 100K
This year: 0.8 per 100K

Influenza-Like Illness (ILI) continues to track well lower than the mild 2015-16 and 2011-12 seasons, but rise for second week in a row (HCoVs?).

Latest U.S. non-SARS-CoV2 syndromic data from BioFire.

Lots of rhinoviruses and some adenoviruses all year.

Flu A, B micro-wave already over. RSV, and PIV back at low levels.

HCoV sharp rise has overall non-COVID respiratory infections near normal.

syndromictrends.com/metric/panel/r…

Out-of-season HCoV surge continues after a year of absence as SARS-CoV2 recedes. HCoV-NL63 potentially post-peak. HCoV-OC43 rise still accelerating. HCoV-229E rising too.

CDC surveillance confirms HCoV surge.
cdc.gov/surveillance/n…

HCoV-NL63 outbreak in Midwest (IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI) region. Peaked?
cdc.gov/surveillance/n…

Florida. Schools open all year. No lockdowns since September. Rhinoviruses and some adenoviruses but nearly no flu (exception region 2, mid-panhandle); PIV accelerated this week. RSV peaked? floridahealth.gov/diseases-and-c…

Sweden week 14. No masks, no lockdowns, no school closures under age 16 -- and a full year with no Flu A, Flu B, or RSV; RSV is finally off the x-axis though. HCoVs continue to rise.

karolinska.se/globalassets/g…

Germany week 14. Rhinoviruses and HCoVs turn down as SARS-CoV2 turns back up. Still no flu.
influenza.rki.de/Wochenberichte…

Brazil. Very lax control measures, and a president who urges people to disregard them. A completely skipped flu season.
apps.who.int/flumart/Defaul…

The global flu chart from WHO.
apps.who.int/flumart/Defaul…

But flu did not disappear everywhere.
apps.who.int/flumart/Defaul…

It wasn't masks, which were never used in many countries where flu disappeared and have also been shown to be ineffective for stopping influenza in many, many studies.

apps.who.int/iris/bitstream…

Japan masks every year, and pushed masks hard in 2019 with no apparent effect. But in 2020-21 flu disappeared with low stringency COVID intervention.
apps.who.int/flumart/Defaul…

The idea mitigations worked but unmitigated SARS-CoV2 just has a higher R (popular now among the same crowd that said "twindemic!" when flu had been gone for months) is way too facile.

Outside of testing ramp up, I don't think we've seen R > 2, even in places without NPIs.

Rhinoviruses bounced right back despite lower R and RSV was gone until recently with comparable R to SARS-CoV2.

HCoVs were gone until SARS-CoV2 declined, then returned even with lockdown.

Plus, as Biden adviser Dr. Michael Osterholm points out, our mitigation just hasn't been very effective.

Maybe in places like Australia and New Zealand where mitigations stopped SARS-CoV2 they also stopped other viruses.

But in countries where SARS-CoV2 went wild? No.

Osterholm: "There is this viral interference"

Viral interference is a well-known (but poorly understood) phenomenon. Interference from rhinovirus is generally thought to have ended the swine flu epidemic in 2009.
thelancet.com/journals/lanmi…

This great short article from @m_soond explains the viral interference theory of this respiratory season:
medium.com/illumination-c…

Overall the season has been so mild that drug store chains took big losses.

Rite Aid CEO Heyward Donigan: "During the fourth quarter our industry was impacted by a historically soft cough, cold and flu season."
forbes.com/sites/brucejap…

The empty pediatric wards usually used for respiratory disease have been converted to deal with the overflow child psychiatric admissions from lockdowns/school closures.

We are now near the end of the *safest* respiratory season for children ever recorded. (And yes, that includes places where schools never closed.)

Yet many places locked children out of school, and some places are still doing so. It's a disgrace.