The Oregon Health Authority said Thursday it estimates the highly infectious delta variant is now responsible for 50% of all new COVID-19 cases in the state.
The meteoric rise of the variant in Oregon mirrors increases in the rest of the United States, although federal officials have been quicker at reporting the prevalence of the strain.
On July 6, the Centers for Disease Control and Prevention announced delta was the source of 51% of infections. Tuesday, the CDC said that figure had grown to 83%, far higher than the estimated share in Oregon. Delta was first detected in India and is formerly known as B.1.617.2.
The delta variant’s prevalence in Oregon, like nationally, is only an estimate because just a small portion of COVID-19 cases -- more than 5% in Oregon, officials say -- are analyzed for variants. The state’s official tally of cases known to be caused by the delta variant now stands at 90.
In the week with data most recently available -- July 4 to July 10 -- the health authority reported the results of its analysis for variants for concern: 21 cases were caused by the delta variant and 15 cases caused by the alpha variant. Four other cases that were analyzed were not variants of concern.
The Oregon Health Authority didn’t immediately respond to questions seeking to clarify if that meant only 40 infections had been analyzed that week for variants.
The emergence of the delta variant in Oregon follows that of the alpha variant -- which was first detected in the United Kingdom and formerly known as B.1.1.7. Alpha dominated Oregon’s COVID-19 cases from April into June.
A recent study found that individuals infected with delta became contagious faster and exhaled about 1,000 times the viral load into the air as people infected with the dominant strain circulating last year. Delta is thought to be at least twice as contagious as the dominant strain last year.
“This means that the risk of COVID-19 has never been greater in unvaccinated populations,” wrote health authority spokeswoman Erica Heartquist in an email Thursday to The Oregonian/OregonLive. “We encourage all households with vaccinated and unvaccinated members, such as children, to remember that the unvaccinated members of our community are at risk and to take appropriate precautions -- masking, distancing, avoiding gatherings with unvaccinated individuals.”
The health authority’s director, Patrick Allen, and state epidemiologist Dr. Dean Sidelinger will hold a news conference Thursday afternoon to discuss Oregon’s increasing COVID-19 cases, which after two months of steady decline in late spring and early summer started rising in early July. The rolling seven-day average of cases have more than doubled in the past two weeks.
Check back on OregonLive.com to hear what Allen and Sidelinger had to say.
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-- Aimee Green; agreen@oregonian.com; @o_aimee