The most transmissible delta type of Covid-19 is spreading in Missouri and Colorado, placing them among the US states with the highest infection rates in the country.
The delta variant, first identified in India, made up 29.1 percent of the genomically sequenced samples in Missouri in the four weeks ending June 5, the latest data on the Centers for Disease Control and Prevention website, which was revealed on Wednesday.
This is the highest percentage in the United States, ahead of Colorado in second place, at 10.9 percent. New Jersey, Arizona and Texas made the top five, with the delta variable making up 7.4 percent, 7.1 percent and 6.5 percent of samples during that period.
These numbers may underestimate the current prevalence of the delta variant in the United States. Anthony Fauci, President Joe Biden’s chief medical advisor, said at a press conference Tuesday that this new strain is forming 20.6% of serial samples in the weeks ending June 19, up from 9.9 percent in the two weeks ending June 5.
Missouri, which has a population of about 6.1 million, reported nearly 4,800 cases in the week ending June 22, according to CDC data. This is the fourth-highest number of cases in the United States, coming after Florida, Texas and California, which are third, second, and number one in the United States by population.
After adjusting for population, Missouri has reported 11.2 new infections per 100,000 people per day for the past seven days. This is the highest rate in the country, and compares to the national average of about 3.4 per day. Colorado, another hotspot for the delta variant, ranks seventh in the United States in terms of total infections per capita, averaging about 6.9 new cases per day per 100,000 people over the past week.
Most of the 10 states with the highest per capita rates of new cases are geographically close to either Missouri or Colorado, making these areas the nation’s coronavirus hotspots — although daily infections remain well below peak levels in the fall and winter.
Louisiana, Arkansas, and Missouri, whose eastern border is on the Mississippi River, are among those states with hot spots and also have some of the lowest rates of first-dose vaccination in the United States. Wyoming, another infection hotspot, borders Colorado and has one of the lowest proportions of the vaccinated population in the country.
An additional challenge in assessing the prevalence of a delta variant in the United States is that the CDC data only shows numbers from states that have reported at least 300 sequences. That may explain the absence of Louisiana, Arkansas, Wyoming and Utah, which also have high infection rates, from the CDC’s data set.