The number of Delta variant COVID-19 cases at Houston Methodist has nearly doubled over the last week and is sixfold higher than in May. The most recent genome sequencing data through the end of June show the Delta variant in our patients now at 42%, up from 20% reported last week. The Delta variant has now surpassed the Alpha variant, which had been the dominant strain in Houston since March 2021, but now presently accounts for only 40% of new infections in our patients. Houston Methodist has seen 139 Delta cases through June 28.


Houston Methodist’s team of infectious disease pathologists, who sequence the genome of every positive COVID-19 strain throughout the hospital system, has calculated the doubling time of the Delta variant to be 7.5 days. Statistical models predict the Delta variant will plateau at 92% of all new infections within the next couple weeks. This pattern in Houston patients is similar to what was seen with the Alpha variant here and in the UK earlier this year, and more recently with the Delta variant in the UK.


Couple this increase with the slight uptick we are seeing this week in overall COVID-19 cases, and it underscores the urgency of increasing vaccination rates to reach herd immunity, as experts say it’s the only way to stop these variants from spreading and to prevent new variants from forming. We have seen a 41% increase in COVID-19 patients at Houston Methodist in the last two weeks. As of July 7, there were 127 Covid-positive patients admitted as inpatients in our hospitals, increased from Sunday’s 107 and last week’s 86.


Research shows the vaccines work well against the Delta variant and almost all infected patients are unvaccinated. While some new studies say the vaccines used in the U.S. have reduced efficacy against infection with Delta, they remain highly effective in preventing serious illness and hospitalization. This is proving to be the case in Israel.


Bottom line, Houston Methodist is urging the unvaccinated in the community to get shots as soon as possible, and if they do not, then they should continue practicing the COVID-19 prevention measures of masking, social distancing, avoiding large crowds, maintaining hand hygiene and other best practices to protect themselves and their loved ones against Delta.