Skip to the content.

October 3, 2021 Analysis of USA state data

Summary: After many weeks with rapid growth in cases (more that six weeks after the delta variant became dominant), most states have turned around, due to changes in measures or due to the herd effect begining to take effect.

Individual state histories

The plots below show the case / hospitalization / deaths data for all 50 states, DC, and PR. The data fits were done using data up until October 2, 2021.

An infection model is setup for each state, calibrated using the case data from that state. Given the time history of infections, projections for hospitalization and death are calculated and shown as curves in the plots below. The degree that hospitalization and death data following the model projections, indicates the ability of this approach to forecast future hospitalization and death.

The green points are the daily cases, the grey points the daily hospitalizations, and indigo points are the daily deaths (each averaged over a week). The case data are used to define the periods for which transmission rate appears to be constant. The vertical lines show where the transmission rate is changed. If the susceptibe fraction is constant (immunity not changing quickly), constant transmission rates lead to steady exponential growth or decline during, which appear as straight lines on these log-scale plots. With immunity growing, these lines are no longer straight - bending downwards due to the herd effect. The curves are the model expectations for cases, hospitalizations, and deaths, and all three are determined from the case data.

For this analysis, a long tail in the delay time between symptoms and hospital admission is included - which improves the model fits to hospitalization data. Now with this correction, the data appear to be consistent with the hypothesis that hospitalization probability is roughly constant (for most states).

The dashed curves separately show the reported cases from the original strains and from variants of concern, divided into two types B.1.1.7 (alpha) and B.1.617.2 (delta).

At the bottom of this page, plots showing the combined forecast for the US are shown.

Alaska

ak

Alabama

al

Arkansas

ar

Arizona

az

California

ca

Colorado

co

Connecticut

ct

District Of Columbia

dc

Delaware

de

Florida

fl

Georgia

ga

Hawaii

hi

Iowa

ia

Idaho

id

Illinois

il

Indiana

in

Kansas

ks

Kentucky

ky

Louisiana

la

Massachusetts

ma

Maryland

md

Maine

me

Michigan

mi

Minnesota

mn

Missouri

mo

Mississippi

ms

Montana

mt

North Carolina

nc

North Dakota

nd

Nebraska

ne

New Hampshire

nh

New Jersey

nj

New Mexico

nm

Nevada

nv

New York

ny

Ohio

oh

Oklahoma

ok

Oregon

or

Pennsylvania

pa

Puerto Rico

pr

Rhode Island

ri

South Carolina

sc

South Dakota

sd

Tennessee

tn

Texas

tx

Utah

ut

Virginia

va

Vermont

vt

Washington

wa

Wisconsin

wi

West Virginia

wv

Wyoming

wy

Comparing prevalence between states

The following plots show the daily cases per 100,000 people in each state, grouped according to the 10 standard federal regions.

prev

USA Forecast

The following plots show the combined US 4 week forecast. The shaded areas are 50%, 80%, and 95% intervals. Overall, case rates are forecast to be declining.

USA

usa

return to case studies