The CDC and US Navy study reveals common symptoms and suggests best protective measures to prevent spread in enclosed environments that clinical labs and pathology groups could use to protect their staff members
Results from a study conducted by the US Navy and the federal Centers for Disease Control and Prevention (CDC) of sailors onboard the USS Theodore Roosevelt during the recent COVID-19 outbreak aboard the ship may be useful for pathologists and clinical laboratory managers. The study also provides public health and infectious disease specialists with an opportunity to learn more about how the SARS-CoV-2 coronavirus spreads in enclosed environments.
The aircraft carrier garnered headlines in April due to a widespread outbreak of the coronavirus among its crew. The investigators asked crewmembers to complete a questionnaire and provide samples for a serological antibody test and molecular diagnostics test, reported the Navy’s Bureau of Medicine and Surgery (BUMED). The goal was to learn more about the disease and how it spreads in high-density environments. The COVID-19 tests were conducted April 20-24 while the ship was docked in Guam.
“This study paints a picture of current and prior SARS-CoV-2 infection among young adults living in close quarters,” said the study’s lead author Dan Payne, PhD, an epidemiologist at the CDC, in the BUMED statement. “This data will contribute to understanding COVID-19 in the US military, as well as among young adults in other close communal environments.”
Participation in the study was voluntary. At the time of testing, a total of 1,417 service members were still on the ship or at the base in Guam, the researchers wrote in their study. Among them, 383 crewmembers agreed to complete the survey and provide a blood sample for an enzyme-linked immunosorbent assay (ELISA) antibody test. Out of that group, 267 also provided nasal swab samples for a reverse transcription polymerase chain reaction (RT-PCR) molecular diagnostic test.
A clinical laboratory team from the Naval Hospital Guam and the Navy and Marine Corps Public Health Center are seen above collecting surveys, nasal swabs, and blood samples from sailors assigned to the aircraft carrier USS Theodore Roosevelt (CVN 71) during the investigation into the COVID-19 outbreak in April. The ship’s medical leaders established an emergency command center, initiated a roving and deep cleaning team, and continually educated the crew on social distancing and proper protective procedures and behaviors, to mitigate the spread of the SARS-CoV-2 coronavirus. (Photo copyright: US Navy.)
The questionnaire sought information about sailors’ demographic factors, health history, symptoms, and preventive behaviors, such as mask wearing and physical distancing. Crewmembers who tested positive for reactive antibodies received an additional test to detect presence of neutralizing antibodies that inhibit the virus.
The median age of participants was 30 years. About 75% were male. Only 28 (7.3%) reported comorbidities such as a history of asthma, diabetes, hypertension, or immunosuppression, which are considered risk factors for developing serious cases of the COVID-19 disease.
Key findings of the CDC/Navy’s study:
228 participants (59.7%) tested positive for reactive antibodies. Of those, 135 (59.2%) tested positive for neutralizing antibodies.
235 participants had previously tested positive in a SARS-CoV-2 diagnostic test. Of those, 212 (90.2%) tested positive for reactive antibodies.
A total of 238 participants had a previous or current SARS-CoV-2 infection. Of these, 18.5% reported no symptoms.
Of the 194 sailors who reported symptoms, 115 (59.3%) sought medical care, and two were hospitalized.
The most frequently reported symptoms were headache (66.5%), loss of taste or smell or both (61.3%); myalgia (56.2%); runny nose (55.7%); and fatigue (55.2%).
The most effective preventive measures were avoidance of common areas, increased physical distancing, and use of face coverings.
“What we saw was that most of the infections were actually mild, in addition to those that were asymptomatic,” Payne told reporters after the study was published, reported CNN. “And this is perhaps different from studies of older Americans, or maybe even those who were hospitalized already, and certainly much different from those with underlying health conditions.”
But with the high number of asymptomatic cases, “symptom-based surveillance might not detect all infections,” noted the researchers, who cautioned that “the analysis was conducted on a convenience sample of persons who might have had a higher likelihood of exposure, and all information was based on self-report, raising the possibility of selection and recall biases.”
In January, the crew of the Roosevelt totaled about 4,800 sailors, reported Defense One. However, after docking in Guam, many sailors were moved to hotel rooms for quarantine. As of May 5, at least 1,156 crewmembers had tested positive for infection, Stars and Stripes reported, and one had died.
Sailors aboard the USS Theodore Roosevelt were examined prior to reboarding the ship following off-ship quarantine or isolation. Only those found to be negative for the coronavirus, were allowed to board the ship. (Photo copyright: US Navy.)
Impact of COVID-19 on the USS Theodore Roosevelt’s Crew
As of April 6, 172 crew members had tested positive for COVID-19, including the ship’s captain Brett Crozier. At that time, 61% of the crew had received clinical laboratory testing and 1,999 sailors had been moved off the ship into quarantine, reported Defense One. By the next day, 270 sailors tested positive, a 57% increase from the previous day.
By April 14, 589 crew members were diagnosed positive for COVID-19. With 92% of the crew tested, 3,922 were found to be negative for the infection. Nevertheless, 4,024 sailors—nearly 83% of the crew—were moved into isolation quarters off-ship to prevent spread of the coronavirus.
In their study, the Navy/CDC researchers concluded: “In this convenience sample of young, healthy US service members experiencing close contact aboard an aircraft carrier, those with previous or current SARS-CoV-2 infection experienced mild illness overall, and nearly 20% were asymptomatic. Approximately one third of participants reported fever, myalgia, and chills and had higher odds of SARS-CoV-2 infection than did persons who reported cough and shortness of breath. Participants reporting anosmia (loss of sense of smell) or ageusia (loss of sense of taste) had 10 times the odds of having infection, compared with those who did not.
“In this sample of intensely exposed subjects, assessed at a single point in time, results demonstrated that antibodies developed and that, at the time of specimen collection, many of these were neutralizing antibodies. … This is a promising indicator of immunity, and in several participants, neutralizing antibodies were still detectable >40 days after symptom onset. Ongoing studies assessing the humoral antibody response over time will aid the interpretation of serologic results in an outbreak investigation such as this.
“These results provide new indications of symptomatology of SARS-CoV-2 infections and serologic responses among a cohort of young US adults living in a congregate environment and contribute to a better understanding of COVID-19 epidemiology in the US military. The findings reinforce the importance of nonpharmaceutical interventions such as wearing a face covering, avoiding common areas, and observing social distancing to lower risk for infection in similar congregate living settings.”
Not all the specific lessons learned from this COVID-19 outbreak aboard a US Navy vessel will be applicable to clinical laboratories and anatomic pathology groups. Nevertheless, it is probable that the data gleaned from the CDC/Navy study aboard the USS Theodore Roosevelt will someday mean civilian Americans can count on improved responses to disease outbreaks from the nation’s testing laboratories.
It can take up to eight days after onset of symptoms for a person’s immune system to develop antibodies, so serological tests are not designed for diagnosing recent or active infections, stated a Mayo Clinic news story. However, Reuters reported that the availability of serological tests is “a potential game changer” because they could identify people who are immune even if they had no symptoms or only mild symptoms.
“Ultimately, this might help us figure out who can get the country back to normal,” Florian Krammer, PhD, told Reuters. Krammer’s lab at the Icahn School of Medicine at Mount Sinai in New York City has developed a serological test. “People who are immune could be the first people to go back to normal life and start everything up again,” he said.
However, some experts advise that the presence of antibodies is not necessarily a “get out of jail free” card when it comes to the coronavirus. “Infectious disease experts say immunity against COVID-19 may last for several months and perhaps a year or more based on their studies of other coronaviruses, including Severe Acute Respiratory Syndrome (SARS), which emerged in 2003,” reported Reuters. “But [the experts] caution that there is no way to know precisely how long immunity would last with COVID-19, and it may vary person to person.”
Additionally, it is also “uncertain whether antibodies would be sufficient protection if a person were to be re-exposed to the virus in very large amounts,” such as in an emergency room or ICU, Reuters reported.
Serological Survey Studies Get Underway Worldwide
Aside from detecting potential immunity, the World Health Organization (WHO) says serological tests could be useful for widespread disease surveillance and epidemiological research.
In the US, the Vitalant
Research Institute is leading several large serological survey or
“serosurvey” studies in which regional blood centers save samples of donated
blood for antibody testing, Science
reported.
Science also reported on a similar WHO initiative in which six countries will pool data from their own antibody studies. And in the Netherlands, blood banks have begun screening thousands of blood donations for presence of antibodies, Wired reported.
FDA Emergency Use Authorization
On March 16, the federal Food and Drug Administration (FDA) announced that it would allow commercial development and distribution of serological tests that “identify antibodies (e.g., IgM, IgG) to SARS-CoV-2 from clinical specimens” without an Emergency Use Authorization (EUA). The agency noted that these tests are “less complex than molecular tests” used to detect active infections, and that the policy change is limited to such testing in medical laboratories or by healthcare workers at the point-of-care. “This policy does not apply to at home testing,” the FDA reiterated.
“Serological tests can play a critical role in the fight against COVID-19 by helping healthcare professionals to identify individuals who have overcome an infection in the past and have developed an immune response,” said FDA Commissioner Stephen M. Hahn, MD (above with President Trump during a Coronavirus Task Force press briefing), in an April 7 press statement. “In the future, this may potentially be used to help determine—together with other clinical data—that such individuals are no longer susceptible to infection and can return to work. In addition, these test results can aid in determining who may donate a part of their blood called convalescent plasma, which may serve as a possible treatment for those who are seriously ill from COVID-19.” (Photo copyright: CNBC.)
FDA Issues First EUA for Rapid Diagnostic Test
Cellex Inc., based in Research Triangle Park, N.C., received the first EUA for its qSARS-CoV-2 serological test on April 1. As with other rapid diagnostic tests (RDTs) under development, the qSARS-CoV-2 test detects the presence of immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in human blood. The biotechnology company’s RDT can be used to test serum, plasma, or whole-blood specimens, stated Cellex, and can produce results in 15 to 20 minutes.
The FDA has authorized use of the antibody test only by laboratories certified under CLIA to perform moderate and high complexity tests. Cellex has set up a COVID-19 website with information about the qSARS-CoV-2 test for clinical laboratories, patients, and healthcare providers.
Other Serological Tests Under Development
Mayo
Clinic Laboratories announced on April 13 that it is ramping up
availability of an internally-developed serological test. “Initial capacity
will be 8,000 tests per day performed at laboratory locations across Mayo Clinic,” stated the announcement.
“Testing will be performed 24 hours a day, and Mayo Clinic Laboratories is working
to ensure turnaround time is as close as possible to 24 hours after receipt of
the sample.”
Emory University in Atlanta announced on April 13 that it will begin deploying its own internally developed antibody test. Initially, testing will be limited to 300 people per day, comprised of Emory Healthcare patients, providers, and staff members. Eventually, testing will be “expanded significantly,” said Emory, with a goal of 5,000 tests per day by mid-June.
RDTs are typically qualitative, meaning they produce a
positive or negative result, stated the Center for Health Security. An ELISA
test “can be qualitative or quantitative,” noted the Center, but it can take
one to five hours to produce results.
A third type of serological test—the neutralization assay—involves infecting a patient’s blood with live coronavirus to determine if antibodies exist that can inhibit growth of the virus. The test takes three to five days in a level 3 biosafety laboratory to produce results. The Straits Times reported on one laboratory in Singapore that developed a neutralization assay to trace the source of COVID-19 infections that originated in Wuhan, China.
Serological testing is another important tool clinical
laboratories and epidemiologists can use to fight and ultimately defeat the
COVID-19 pandemic and is worth watching.
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