According to the UCSF study, variations in a specific gene in a system of genes responsible for regulating the human immune system appears to be the factor in why about 10% of those who become infected with the virus are asymptomatic.
These scientific insights did not receive widespread news coverage but will be of interest to clinical laboratory managers and pathologists who oversee SARS-CoV-2 testing in their labs.
“Some people just don’t have symptoms at all,” Jill Hollenbach, PhD (above), Professor of Neurology atUCSF’s Weill Institute for Neurosciences and lead researcher in the study, told NBC News. “There’s something happening at a really fundamental level in the immune response that is helping those people to just completely wipe out this infection.” Identifying a genetic reason why some people are asymptomatic could lead to new precision medicine clinical laboratory diagnostics for COVID-19. (Photo copyright: Elena Zhukova /University of California San Francisco.)
Fortunate Gene Mutation
According to the Centers for Disease Control and Prevention’s (CDC) COVID Data Tracker, as of April 5, 2023, a total of 104,242,889 COVID-19 cases have been reported in the United States. However, according to a CDC Morbidity and Mortality Weekly Report (MMWR), “Traditional methods of disease surveillance do not capture all COVID-19 cases because some are asymptomatic, not diagnosed, or not reported; therefore, [knowing the true] proportion of the population with SARS-CoV-2 antibodies (i.e., seroprevalence) can improve understanding of population-level incidence of COVID-19.”
She also participates in the COVID-19 HLA and Immunogenetics Consortium, a group of academic researchers, clinical laboratory directors, journal editors, and others who examine the role of HLA variations in determining COVID-19 risk.
Hollenbach’s research identified an HLA variant—known as HLA-B*15:01—that causes the human immune system to react quickly to SARS-CoV-2 and “basically nuke the infection before you even start to have symptoms,” she told NPR.
“It’s definitely luck,” she added. “But, you know, this [gene] mutation is quite common. We estimate that maybe one in 10 people have it. And in people who are asymptomatic, that rises to one in five.”
“HLA variants are among the strongest reported associations with viral infections,” the UCSF study notes. So, the researchers theorized that HLA variations play a role in asymptomatic SARS-CoV-2 infections as well.
To conduct their study, shortly after the SARS-CoV-2 outbreak in 2020, the researchers recruited approximately 30,000 volunteer bone marrow donors from the National Marrow Donor Program to respond to periodic questions via a smartphone app or website. Because HLA variations can determine appropriate matches between donors and recipients, the database includes information about their HLA types.
Each week, respondents were asked to report if they had been tested for SARS-CoV-2. Each day, they were asked to report whether they had symptoms associated with COVID-19. “We were pretty stringent in our definition of asymptomatic,” Hollenbach told NBC News. “[The respondents couldn’t] even have a scratchy throat.”
The researchers eventually identified a cohort of 1,428 people who had tested positive for SARS-CoV-2 between February 2020 and April 30, 2021, before vaccines were widely available. Among these individuals, 136 reported no symptoms for two weeks before or two weeks after a positive test.
“Overall, one in five individuals (20%) who remained asymptomatic after infection carried HLA-B*15:01, compared to 9% among patients reporting symptoms,” the researchers wrote in their medRxiv preprint. Study participants with two copies of the gene were more than eight times more likely to be asymptomatic.
The UCSF researchers also looked at four other HLA variants and found none to be “significantly associated” with lack of symptoms. They confirmed their findings by reproducing the HLA-B association in two additional independent cohorts, one from an earlier study in the UK and the other consisting of San Francisco-area residents.
Individuals in the latter group had either tested positive for SARS-CoV-2 or reported COVID symptoms, and their DNA was analyzed to determine their HLA types.
Pre-existing T-Cell Immunity May Reduce Severity of COVID-19 Infection
The UCSF researchers also attempted to determine how HLA-B*15:01 plays a role in knocking out SARS-CoV-2 infections. They noted previous research that indicated previous exposure to seasonal coronaviruses, such as common cold viruses, could limit the severity of COVID-19. The scientists hypothesized that pre-existing T-cell immunity in HLA-B carriers may be the key.
The COVID-19 HLA and Immunogenetics Consortium website describes how HLA and T-cells work together to ward off disease. HLA “proteins are found on the surface of all cells except red-blood cells.” They’re “like windows into the inner workings of a cell,” and T-cells use the molecules to determine the presence of foreign proteins that are likely signs of infection. “Activated T-cells can kill infected cells, or activate B-cells, which produce antibodies in response to an infection,” the website explains.
Hollenbach’s research team analyzed T-cells from pre-pandemic individuals and observed that in more than half of HLA-B carriers, the T-cells were reactive to a SARS-CoV-2 peptide. The scientists corroborated the hypothesis by examining crystal structures of the HLA-B*15:01 molecule in the presence of coronavirus spike peptides from SARS-CoV-2 and two other human coronaviruses: OC43-CoV and HKU1-CoV.
“Altogether, our results strongly support the hypothesis that HLA-B*15:01 mediates asymptomatic COVID-19 disease via pre-existing T-cell immunity due to previous exposure to HKU1-CoV and OC43-CoV,” the researchers wrote.
Can Genes Prevent COVID-19 Infections?
Meanwhile, researchers at The Rockefeller University in New York City are attempting to go further and see if there are mutations that prevent people from getting infected in the first place. NPR reported that they were seeking participants for a study seeking to identify so-called “superdodger” genes.
Study participants identified as possibly having superdodger genes receive a kit designed to collect saliva samples, after which the researchers sequence the respondents’ genomes. “We hope that in a group of 2,000 to 4,000 people, some people will have genetic mutations that tell us why they’re resistant to infection,” Casanova told NPR.
All this genetic research is in very early stages. But results are promising and may lead to new precision medicine clinical laboratory tests for identifying people who are predisposed to having an asymptomatic response to COVID-19 infection. That in turn could help scientists learn how to moderate or even eliminate symptoms in those unfortunate people who suffer the typical symptoms of the disease.
The global monkeypox outbreak that emerged last spring appears to have subsided in the US and Europe, though it remains to be seen if the disease can be completely eradicated, according to multiple media reports. As of Oct. 26, 2022, the Centers for Disease Control and Prevention (CDC) reported a 7-day rolling average of 30 cases per day in the US, down from a peak of nearly 440/day in early August.
Cases are also down in cities that earlier reported heavy outbreaks. For example, the New York City Health Department reported a 7-day average of just two cases per day on Oct. 25, compared with 73/day on July 30.
And the San Francisco Department of Public Health announced on Oct. 20 that it would end the city’s public health emergency on monkeypox (MPX) effective on Oct. 31. “MPX cases have slowed to less than one case per day and more than 27,000 San Franciscans are now vaccinated against the virus,” the agency stated in a press release.
“Once again, we caution that a declining outbreak can be the most dangerous outbreak, because it can tempt us to think that the crisis is over and to let down our guard,” said World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus, PhD, in an Oct. 12 global press briefing. “That’s not what WHO is doing. We are continuing to work with countries around the world to increase their testing capacity, and to monitor trends in the outbreak.” Clinical laboratories should not assume the outbreak has passed but continue to be vigilant and prepared for increased demand in monkeypox testing. (Photo copyright: ITU Pictures.)
Changing Behavior Lowers Infection Rates
In addition to high vaccination rates, public health experts have attributed the decline to behavioral changes among at-risk groups. “There were really substantial changes among men who have sex [with] men,” infectious disease physician Shira Doron, MD, of Tufts Medical Center in Boston, told ABC News.
On September 2, the CDC published the results of a survey indicating that about half of men who have sex with men “reported reducing their number of sex partners, one-time sexual encounters, and use of dating apps because of the monkeypox outbreak.”
Another likely factor is the disease’s limited transmissibility. “Initially, there was a lot of concern that monkeypox could spread widely at daycares or in schools, but, overall, there has been very little spread among children,” NPR reported.
But citing multiple studies, the NPR story noted “that often there isn’t very much virus in the upper respiratory tract,” where it might spread through talking or coughing. “Instead, the highest levels of virus occur on sores found on the skin and inside the anus.”
These studies, along with earlier research, “explain why monkeypox is spreading almost exclusively through contact during sex, especially anal and oral sex, during the current outbreak,” NPR reported.
Monkeypox Could Mutate, experts say
Despite the promising numbers, public health experts are warning that monkeypox could remain as a long-term threat to public health. According to an article in Nature, “At best, the outbreak might fizzle out over the next few months or years. At worst, the virus could become endemic outside Africa by reaching new animal reservoirs, making it nearly impossible to eradicate.”
In addition to the limited transmissibility of the virus, Nature noted that the outbreak stems from a relatively mild form of the pathogen and is rarely fatal. As of Oct. 28, the CDC reported a total of just six confirmed deaths in the US out of a total of 28,302 confirmed cases since the first infections were reported in May.
“I have no confidence that all the people who need to be tested are being tested,” she told Nature. She expressed concerns that people could resume risky behavior if they think the danger has passed.
Another question is whether currently available vaccines offer long-lasting protection. And though reported case numbers are down in the US and Europe, they are rising in parts of Africa and South America, Nature noted.
Gottlieb’s Dire Prediction
The decline in new infections followed dire warnings last summer about the possible consequences of the outbreak. In his New York Times op-ed, former Gottlieb criticized the CDC for being slow to test for the virus. He wrote, “[I]f monkeypox gains a permanent foothold in the United States and becomes an endemic virus that joins our circulating repertoire of pathogens, it will be one of the worst public health failures in modern times not only because of the pain and peril of the disease but also because it was so avoidable.”
At the time of his writing, Gottlieb was right to be concerned. On July 29, the CDC reported a seven-day moving average of 390 reported cases per day. According to the federal agency, a reported case “Includes either the positive laboratory test report date, CDC call center reporting date, or case data entry date into CDC’s emergency response common operating platform, DCIPHER.”
Quashing the outbreak, Gottlieb estimated, would have required about 15,000 tests per week among people presenting symptoms resembling monkeypox. But between mid-May and the end of June, he noted, the CDC had tested only about 2,000 samples, according to the federal agency’s July 15 Morbidity and Mortality Weekly Report (MMWR).
As a remedy, Gottlieb called on the Biden administration to re-focus the CDC’s efforts more on disease control “by transferring some of its disease prevention work to other agencies,” including the FDA.
Multiple recent studies reveal a substantial number of patients continue to delay needed healthcare in the months since the onset of the SARS-CoV-2 outbreak
Based on an analysis of hospital emergency department (ED) usage, federal researchers concluded that patients continue to be cautious when visiting healthcare providers, including clinical laboratories, and that people are altering how they seek and utilize emergency care due to the COVID-19 pandemic. This not only reduces the number of typical test orders from the ER to the hospital lab, but also reduces the source of inpatient admissions.
Between March 29 and April 25 of this year, facilities the CDC examined recorded 1.2 million visits to EDs, compared to 2.1 million visits between March 31 and April 27 of last year. The steepest decrease in patient demographics was for individuals under the age of 14, women, and people living in the Northeast region.
The CDC’s data showed that 12% of ED visits were for children in pre-pandemic 2019, which dropped to 6% during the 2020 pandemic period. The CDC included ED visits from hospitals in 47 states (excluding Hawaii, South Dakota, and Wyoming) and captured information from approximately 73% of ED visits in the US.
Delaying Healthcare Visits Worsens Medical Conditions, Reduces Revenues
ED visits are an important referral source for inpatient admissions. Fewer patients in EDs means lost revenue for hospitals. However, one positive aspect of the waning number of ED visits is that it may be keeping patients with non-emergency situations away from emergency departments, thus reducing the overuse of costly ED visits. But healthcare professionals are concerned that individuals also may be avoiding or delaying care when needed, which could worsen medical situations and outcomes.
“We saw people, with COVID-19 and without, coming into the ED who were very ill,” Vik Reddy, MD, Chief Medical Officer at Wellstar Kennestone Hospital and Wellstar Windy Hill Hospital in the Atlanta area, told Modern Healthcare. He noted that some patients delayed care for critical non-COVID-19 illnesses. “The good news is that we’re seeing that trend reverse this time around. It was scary in March when we knew that people weren’t coming into the ED for heart attacks.”
The NSSP’s analysis concluded that the report’s findings were subject to at least four limitations:
The number of hospitals reporting to NSSP changes over time as facilities are added or closed. For example, 3,173 hospitals reported data in April of 2019, while 3,467 reported data in April 2020.
Diagnostic categories rely on the use of specific codes, which were missing in 20% of the ED visits reported.
NSSP coverage is not uniform across or within all the participating states.
The analysis is limited only to ED visits and does not take into account patients who did not go to an ED, but instead received treatment in other healthcare environments, such as urgent care clinics.
Additional Studies Show Patients Avoiding Hospital EDs, Delaying Care
Other sources also are reporting similar findings regarding consumer attitudes towards seeking medical care during the COVID-19 pandemic. A PricewaterhouseCoopers survey released in May found that about 45% of 2,500 consumers surveyed plan to forgo their annual physical in 2020, due to the pandemic, Modern Healthcare reported.
In addition, an Optum Consumer Pulse Survey released in May found that nearly 20% of 700 surveyed individuals stated they were likely to avoid hospital EDs even if they were showing signs of a heart attack or appendicitis. Another 40% stated they were likely to avoid the ED if they had a cut that required stitches.
The article also states that almost 94 million people have delayed medical care due to the COVID-19 pandemic, and that 66 million of those individuals needed medical care unrelated to the virus but did not receive it.
These studies and others are showing a pattern. The COVID-19 pandemic has changed when and where patients access healthcare, and if the trend continues, it could have a long-term impact on clinical laboratories. Since fewer people are seeking medical care, fewer laboratory tests are being ordered and performed, which means less work and revenue for the nations’ hospital and independent clinical labs.