Between Aug. 25 and Sept. 1, investigators from the tested nearly 3,000 Jefferson County residents for the to detect the presence of the virus in participants’ nasal swabs by the polymerase chain reaction (PCR) method and for the presence of antibodies against the virus in their blood.

The results showed that approximately 1.1% of all the participants tested positive for active coronavirus infections. Among vaccinated participants only 0.7% had an active infection, while nearly 5% of unvaccinated participants were actively infected. This number would roughly correspond to 7,260 active infections in the county, a nearly tenfold increase in infection rates over the rates measured in April, despite a sharp increase in vaccinated residents, as shown in Figure 1.

As in previous testing rounds, the team also tested for antibodies in participants. They found that independent of their vaccination status, in both the sampled and volunteer groups, nearly 16% of the participants had natural infection antibodies against the virus suggesting that they must have been infected by the virus in the recent past. These data indicate that in the last few months, at least 100,000 adults in Jefferson County have had COVID-19.

“These results highlight the steep rise in coronavirus infections in our community and provide a startling snapshot of the current state of the pandemic,” said Aruni Bhatnagar, director of the Envirome Institute. “Our estimates suggest that the number of infected individuals may be twice as high as that indicated in public records.

“Our work shows the vaccine is working as intended. Our population was almost 90% vaccinated, much higher than the 64% of fully vaccinated county residents. In the entire cohort, vaccinated people were over 12 times less likely to be infected compared with unvaccinated people. Though in our volunteer group, 65% of the active infections were in fully vaccinated individuals who had received the vaccine earlier this year. Most reported no or mild allergy-like symptoms and did not recognize that it may be a COVID infection thus did not think they needed to get tested.”

The study also provided estimates of where in Jefferson County the infections are most prevalent. To identify infection rates in different areas, the researchers classified the participants into neighborhood zones, as shown in Figure 2.

The highest rate of active infection was found in Zone 3A, or far southwestern Jefferson County. The highest rate of those recently having had an infection was found in Zone 3B, central southern Jefferson County, as shown in Figure 3.

Participants from Zone 3B also reported lower rates of vaccination, although vaccination rates were lowest in Zone 1B in western Jefferson County, as shown in Figure 4.

“Even though nearly 90% of the participants in the entire study population were vaccinated, we had areas that reported as low as 60% vaccination, and the persistence of infection in some geographical areas seems to be related to lower rates of reported vaccination,” said Rachel Keith, associate professor of environmental medicine at UofL who conducted the study. “Our results show that much work remains to be done and that knowing that rates of infection are high in their community may be an added incentive for some individuals to get vaccinated.

“Additionally, knowing that fully vaccinated individuals may still get an active infection allows those individuals to take additional precautions such as masking or testing which helps keep the community safe, including any young or immunocompromised friends and families who may need extra protection.”

“The vaccine is very effective. Nearly 96% of vaccinated individuals had detectable levels of antibodies against the virus in their blood. However, in a small number of people (less than 0.6%) the levels of antibodies were undetectable in our assay, even though these individuals were fully vaccinated,” Keith said. “The lack of a measurable response in some individuals even after vaccination may be due to their health and immune status. We are analyzing our results to find out more about why some rare individuals do not develop high antibody levels in response to vaccination.”

Using the data from more than 7,000 individuals tested over the past year, the team is trying to identify personal and environmental characteristics that increase the risk for coronavirus infection and how vaccination reduces this risk.

For this round of testing, the team collected samples at 13 locations across Jefferson County. Active coronavirus infections were analyzed by Bluewater Labs and antibodies against the virus were assayed at at the .

To randomly sample people from all parts of the city and to include proportional number of individuals of different age and race/ethnicity, researchers at UofL partnered with Westat to mail approximately 30,000 letters asking people to participate in the study. Nearly 1,000 people who responded to this invitation were tested and an additional 1,886 booked their own appointments after hearing about the study in the news or on social media.

This study was supported in part by a contract with the Centers for Disease Control and Prevention.

Since warmer weather is known to decrease the transmission of other coronaviruses, researchers at the University of Louisville’s , the Johns Hopkins University School of Medicine and the U.S. Department of Defense Joint Artificial Intelligence Center theorized that atmospheric temperature also would affect transmission of SARS-CoV-2. To find out, they compared temperature data and logged cases of COVID-19 in 50 countries in the Northern Hemisphere between Jan. 22 and April 6.

The data showed that as temperatures rose, the rate of increase in new cases of COVID-19 decreased.

“Although this is typical and expected behavior for most members of the coronavirus family, SARS-CoV-2’s rapid spread and lethality have been atypical and unexpected. The confirmation of the SARS-CoV-2 temperature sensitivity has important implications for anticipating the course of the current pandemic,” said Adam Kaplin, of Johns Hopkins, an author of the study.

The researchers compared daily low temperature and relative humidity data with logged COVID-19 cases in the 50 Northern Hemisphere countries. The data showed that between 30 and 100 degrees Fahrenheit, for every 1 degree Fahrenheit increase in temperature, COVID-19 cases declined by 1%, and for every 1 degree decrease in temperature, cases would be predicted to rise by 3.7%.

“Of course, the effect of temperature on the rate of transmission is altered by social interventions like distancing, as well as time spent indoors and other factors. A combination of these factors ultimately will determine the spread of COVID-19,” said Aruni Bhatnagar, co-author and director of the Brown Envirome Institute.

In the United States, sharp spikes in COVID-19 have been seen over the summer, but the researchers noted that based on the data they analyzed, cooler summer temperatures may have resulted in an even higher number of cases.

“Although COVID-19 is an infectious disease that will have non-temperature dependent transmission, our research indicates that it also may have a seasonal component,” Bhatnagar said. “This means that this winter could bring a serious surge on top of the regular transmission.”

The research, published as a preprint on MedRxiv, also indicates that the correlation between temperature and transmission was much greater than the association between temperature and recovery or death from COVID-19.

We have been bombarded with the notion that bacteria are bad for us. You probably also have heard that germs are becoming more and more resistant to antibiotics, leaving us vulnerable to diseases that we thought were conquered. As scientists develop ever-more-powerful medications to fight bacterial infections, the bacteria are fighting back, and sometimes seem to be winning.

Will we eventually enter a post-antibiotic era where simple infections can kill us?

Deborah Yoder-Himes, PhD, assistant professor in the Department of Biology at the University of Louisville, assures us we are not yet doomed, but we do need to have a battle plan.

“If we take steps now to combat the rising rates of antibiotic resistance, develop new antibiotics and secure these medicines for future use, we can win the war against these bugs,” Yoder-Himes said.

How do we do this?

At the next Beer with a Scientist, Yoder-Himes will discuss how most bacteria are actually good for us, how pathogenic bacteria evolve to resist our most potent medications and how science can preserve our ability to fight illness-causing infections.

The talk begins at 8 p.m. on Wednesday, April 18, at Against the Grain Brewery, 401 E. Main St. in Louisville. A 30-minute presentation will be followed by an informal Q&A session.

Admission is free. Purchase of beer, other beverages or menu items is not required but is encouraged.

Watch for info on the next Beer with a Scientist, scheduled for May 16.