One of the more vexing qualities of the COVID-19 virus is that a person infected with it can be contagious for days before they begin to show symptoms. Because of this, the individual might feel perfectly well as they go to the grocery store, or to a playground with their children, or to a friend's house, even as they shed infectious viral particles.
Because so many COVID-19 infections occur when an asymptomatic person exposes others to the virus, public-health experts have sought to better understand the timeline of when a person is exposed to the virus, when their infection can be detected, when they become able to infect others, and when they might start to show symptoms.
To contribute to that effort, a team of researchers has teamed up with the Pasadena Public Health Department (PPHD) to study how the amount of the virus changes in a person's body after they are infected. The researchers are in the laboratory of Rustem Ismagilov, the Ethel Wilson Bowles and Robert Bowles Professor of Chemistry and Chemical Engineering and director of the Jacobs Institute for Molecular Engineering for Medicine.
Alex Winnett, a biology graduate student and one of the researchers working on the study, says he became interested in learning more about the epidemiology of COVID-19 while volunteering at the Greater Los Angeles Veterans Affairs Medical Center at the onset of the pandemic last spring.
"While developing infection-control policies, gaps in our knowledge about COVID-19 transmission made it challenging to know how to most effectively prevent and stop outbreaks," he says. "For example, during an outbreak in one of our nursing homes, we started testing all residents on a regular interval to identify asymptomatic but potentially infectious residents. But the question was what the best interval would be to minimize spread."
Members of the Ismagilov lab started talking about how they could design a study that would help answer this question. The primary goal of the ongoing study is to observe how the amount of virus in a person's body (their so-called viral load) changes over time after they have been infected. By tracking this on a twice-daily basis, the research team is learning how long it takes a person to become infectious after exposure and at what point the infection can first be detected in different sample types, such as saliva or a nasal swab, and by different types of COVID-19 tests.
"What we want is to observe their conversion from uninfected to infected," Winnett says. To best do this, the researchers recognized they would need a large sample of people who were not yet infected but were at high risk for infection. "The people with the highest risk of catching COVID are those who live with someone who has a COVID infection," he says. "We thought that Pasadena Public Health and their contact tracers would be valuable for helping us reach these people."
Contact tracers are people employed by public health agencies to track down where a person sick with an infection might have gotten it and to whom they might have spread it. So, for example, if a person comes down with a COVID-19 infection, they may be asked by a contact tracer where they have been and who they have been around, including their household contacts.
Contact tracing is an important part of controlling the spread of diseases like COVID-19 because it allows public health departments to let people know they have been exposed to the virus so that those people can quarantine and avoid spreading it to others. Because PPHD contact tracers were already speaking to people in the city with COVID-19, they also would be able to identify potential research participants for the Ismagilov lab's study.
The lab worked with PPHD director Ying-Ying Goh, epidemiologist Matthew Feaster, and public health nurse Colten Tognazzini to develop the study. When contact tracers reach out to a household where at least one person with COVID-19 is living with people still uninfected with the virus, the tracers ask if the other members of the household would like to participate in the research, explains Matt Cooper, graduate student in biochemistry and molecular biophysics and another member of the research team.
The team has also gotten recruitment support from many local healthcare providers, testing sites, community groups, and Caltech's Student Wellness Services.
If these potential study subjects are interested, the contact tracers connect them with the Ismagilov lab's study coordinators, Noah Schlenker and Jessica Reyes. If the subjects agree to participate, they provide demographic and health information, and receive kits with which they can collect samples themselves each morning and each evening. Each day, a courier picks up the samples and delivers them to the Ismagilov lab, where researchers monitor viral load and look for evidence of new infections, Cooper adds. This routine continues for about two weeks.
"We have a pretty sizeable sample pool-150 people from 50 households and 4,000 samples-and we are still enrolling people," says Emily Savela, graduate student in bioengineering and research team member.
Though the study is ongoing, the researchers have submitted one preprint paper discussing their findings so far and are working on a second preprint paper. They hope to have the first preprint peer reviewed and published in the near future.
Other members of the research team are Reid Akana, graduate student in bioengineering; Jacob Barlow, graduate student in bioengineering; Alyssa Carter, research lab technician; Jenny Ji, undergraduate researcher; study volunteers Jessica Leong and Jess Slagle; Michael Porter, graduate student in chemical engineering; Anna Romano, associate research scientist; Natasha Shelby, the study administrator and Ismagilov lab's research manager, and Rustem Ismagilov.
