Gene sequencing is enabling disease tracking in new ways that include retesting laboratory specimens from before the SARS-CoV-2 outbreak to determine when it arrived in the US
On February 26 of this year, nearly 200 executives and employees of neuroscience-biotechnology company Biogen gathered at the Boston Marriott Long Wharf hotel for their annual leadership conference. Unbeknownst to the attendees, by the end of the following day, dozens of them had been exposed to and become infected by SARS-CoV-2, the coronavirus that causes the COVID-19 illness.
Researchers now have hard evidence that attendees at this meeting returned to their communities and spread the infection. The findings of this study will be relevant to pathologists and clinical laboratory managers who are cooperating with health authorities in their communities to identify infected individuals and track the spread of the novel coronavirus.
This “superspreader” event has been closely investigated and has led to intriguing conclusions concerning the use of genetic sequencing to revealed vital information about the COVID-19 pandemic. Recent improvements in gene sequencing technology is giving scientists new ways to trace the spread of COVID-19 and other diseases, as well as a method for monitoring mutations and speeding research into various treatments and vaccines.
Genetic Sequencing Traces an Outbreak
“With genetic data, a record of our poor decisions is being captured in a whole new way,” Bronwyn MacInnis, PhD, Director of Pathogen Genomic Surveillance at the Broad Institute of MIT and Harvard, told The Washington Post (WaPo) during its analysis of the COVID-19 superspreading event. MacInnis is one of many Broad Institute, Harvard, MIT, and state of Massachusetts scientists who co-authored a study that detailed the coronavirus’ spread across Boston, including from the Biogen conference.
Titled, “Phylogenetic Analysis of SARS-CoV-2 in the Boston Area Highlights the Role of Recurrent Importation and Superspreading Events,” the paper explains how the researchers “sequenced and analyzed 772 complete SARS-CoV-2 genomes from the region” in order to investigate how the virus was introduced and spread through the area. They traced a specific mutation in the virus—“a simple switch of two letters in the virus’ 30,000-character genetic code,” WaPo reported.
What they discovered is both surprising and enlightening. According to WaPo’s report, at least 35 new cases of the virus were linked directly to the Biogen conference, and the same strain was discovered in outbreaks in two homeless shelters in Boston, where 122 people were infected. The variant tracked by the Boston researchers was found in roughly 30% of the cases that have been sequenced in the state, as well as in Alaska, Senegal, and Luxembourg.
“The data reveal over 80 introductions into the Boston area, predominantly from elsewhere in the United States and Europe. We studied two superspreading events covered by the data, events that led to very different outcomes because of the timing and populations involved. One produced rapid spread in a vulnerable population but little onward transmission, while the other was a major contributor to sustained community transmission,” the researchers noted in their study abstract.
“The same two events differed significantly in the number of new mutations seen, raising the possibility that SARS-CoV-2 superspreading might encompass disparate transmission dynamics. Our results highlight the failure of measures to prevent importation into [Massachusetts] early in the outbreak, underscore the role of superspreading in amplifying an outbreak in a major urban area, and lay a foundation for contact tracing informed by genetic data,” they concluded.
Genetic Sequencing and Mutation Tracking
The use of genetic sequencing to trace the virus could inform measures to control the spread in new ways, but currently, only about 0.33% of cases in the United States are being sequenced, MacInnis told WaPo, and that not sequencing samples is “throwing away the crown jewels of what you really want to know.”
Another role that genetic sequencing is playing in this pandemic is in tracking viral mutations. One of the ways that pandemics worsen is when viruses mutate to become deadlier or more easily spread. Scientists are using genetic sequencing to monitor SARS-CoV-2 for such mutations.
A group of scientists at Texas A&M University led by Yue Xing, PhD, published a paper titled, “MicroGMT: A Mutation Tracker for SARS-CoV-2 and Other Microbial Genome Sequences,” which explains that “Although most mutations are expected to be selectively neural, it is important to monitor if SARS-CoV-2 will eventually evolve to be a stronger or weaker infectious agent as time goes on. Therefore, it is vital to track mutations from newly sequenced SARS-CoV-2 genome.”
Another group of researchers have identified such a mutation. “A SARS-CoV-2 variant carrying the Spike protein amino acid change D614G has become the most prevalent form in the global pandemic. Dynamic tracking of variant frequencies revealed a recurrent pattern of G614 increase at multiple geographic levels: national, regional, and municipal,” Bette Korber, PhD and her colleagues wrote in “Tracking Changes in SARS-CoV-2 Spike: Evidence That D614G Increases Infectivity of the COVID-19 Virus,” published in Cell. Korber is a Laboratory Fellow at Los Alamos National Laboratory and visiting faculty at Santa Fe Institute.
Korber’s findings are important because the mutation the scientists identified appears to have a fitness advantage. “Our data show that, over the course of one month, the variant carrying the D614G Spike mutation became the globally dominant form of SARS-CoV-2,” they wrote. Additionally, the study noted, people infected with the mutated variant appear to have a higher viral load in their upper respiratory tracts.
Genetic Sequencing, the Race for Treatments, Vaccines, and Managing Future Pandemics
A vaccine is the best hope for stopping a pandemic, but short of a vaccine, an effective clinical laboratory treatment is the next best thing. And as Dark Daily reported in “Advances in Gene Sequencing Technology Enable Scientists to Respond to the Novel Coronavirus Outbreak in Record Time with Medical Lab Tests, Therapies,” genetic sequencing is quickly becoming a critical tool to develop both.
If, as Fauci and Morens predict, future pandemics are likely, improvements in gene sequencing and analysis will become even more important for tracing, monitoring, and suppressing outbreaks. Clinical laboratory managers will want to watch this closely, as medical labs that process genetic sequencing will, no doubt, be part of that operation.
Emerging Pandemic Diseases: How We Got to COVID-19 Advances in Gene Sequencing Technology Enable Scientists to Respond to the Novel Coronavirus Outbreak in Record Time with Medical Lab Tests, Therapies