In a worrying development, COVID-19 levels in wastewater have significantly jumped across the United States, indicating that the summer spike in cases is continuing to grow. According to estimates released by the U.S. Centers for Disease Control and Prevention (CDC) on Friday, national virus measurements in sewage reached "high" levels for the first time this summer. The CDC reported that COVID-19 is either growing or possibly growing in 44 states and the nation's capital.

California, for the first time since the winter, has reported "very high" levels of coronavirus in its wastewater, surpassing last summer's levels. Joining California in this category are Arkansas, Florida, Maryland, Nevada, Oregon, and Texas. Additionally, 19 other states across the country, representing every region, have reported high coronavirus levels in sewage.

Notably, in Northern California, two major sewersheds covering San Jose and Palo Alto in Santa Clara County, the region's most populous county, have reported high levels of the virus in wastewater. Furthermore, the rate of positive COVID-19 test results in California is nearing last summer's peak. In the week ending July 8, 13% of reported tests came back positive, compared to 4.8% for the same week a month earlier. This positive test rate is approaching last summer's peak of 13.1% in late August and early September.

Los Angeles County, the most populous county in the country, has also seen a significant jump in coronavirus levels in wastewater. Alongside this increase, the county has observed a rise in the number of cases, emergency department visits, and hospitalizations for COVID-19, prompting the L.A. County Department of Public Health to state that it is too early to determine whether there will be a larger summer wave compared to last year.

The rise in COVID-19 cases is not limited to California. Health officials across the nation are closely monitoring the surge in infections. The New York City Department of Health and Mental Hygiene has recently urged residents to consider wearing masks, particularly in crowded indoor settings and for higher-risk individuals, as cases increase in the city.

The concerning increase in infections coincides with the emergence of a new class of subvariants called FLiRT, estimated to be 20% more transmissible than the dominant subvariant of the winter. For the two-week period ending July 6, approximately 70.5% of COVID specimens nationwide were of the FLiRT subvariants - known as KP.3, KP.2, and KP.1.1 - up from 54.9% a month earlier.

The CDC has identified no states where the summer wave of COVID-19 is declining or possibly declining. Three states, Hawaii, New Mexico, and Oregon, have either stable or uncertain trends in COVID-19 cases, according to the CDC. Data for Missouri, Wisconsin, and Wyoming were not available at the time of reporting.

Health experts, including Dr. Elizabeth Hudson, Regional Chief of Infectious Disease at Kaiser Permanente Southern California, remain cautious about the situation. As the country moves past the Fourth of July holiday, traditionally associated with increased social gatherings, it remains to be seen whether the upward trajectory of cases will continue.

The increase in COVID-19 infections and the potential for a summer surge highlight the ongoing need for vigilance in adhering to preventative measures, including vaccination, wearing masks in high-risk settings, and practicing social distancing.