Lower COVID-19 viral loads found in asymptomatic children
In the first large study looking at SARS-CoV-2 viral loads (VL) in asymptomatic children, researchers found that VL were 3 to 4 logs lower compared with symptomatic children, which was consistent with the difference in median cycle threshold (Ct) values—10.3 cycles—between the two groups.
This finding, published yesterday in the Journal of Clinical Microbiology, held true across age (0 to 17 years old), race and ethnicity, sex, and institution, although the researchers found that both the magnitude of Ct difference and the VL lessened with older subgroups. SARS-CoV-2 is the virus that causes COVID-19.
Polymerase chain reaction (PCR) tests were used for initial COVID-19 detection, and in a press release from Ann & Robert H. Lurie Children's Hospital in Chicago, senior author Nira Pollock, MD, PhD, says, "Many of the asymptomatic kids in our study likely would have tested negative using the rapid tests based on our understanding of the limits of detection of those tests. Our findings should raise caution about using low sensitivity tests for asymptomatic screening programs in pediatric populations."
Across nine health institutions in the United States and Canada, the researchers looked at 339 asymptomatic and 478 symptomatic children from March to July. For the purpose of the study, symptomatic children had at least two symptoms.
The median adjusted Ct value was 8.6 cycles in asymptomatic children and -1.7 cycles in symptomatic children. Median VL was 2.0 X 103 in asymptomatic children and 1.3 X 107 in symptomatic children. Lead author Larry Kociolek, MD, says in the release, "Even the groups of asymptomatic kids with highest viral load in our study still had lower viral loads than the children with symptoms."
Asymptomatic children with diabetes who had recent contact with someone who had COVID-19 were most likely to be in the top 25% of asymptomatic VL, and those with more recent asymptomatic infections also had higher VL. Immunocompromised children did not seem to significantly differ.
The researchers say their study raises questions about peak VL in asymptomatic children, how quickly VL may rise and decline after initial infection, and how the findings affect transmission.
Oct 22 J Clin Microbiol study
Oct 22 Lurie Children's Hospital press release
A summer flight to Ireland led to a 59-person COVID outbreak
Despite implementing safety precautions, one summer flight into Ireland led to a 59-person outbreak in six of the country's eight health regions. Tests eventually confirmed that 13 (26.5%) of the original 49 passengers were positive for SARS-CoV-2, with the other 46 infected via contact with infected passengers.
In the Eurosurveillance study, researchers looked at four separate passenger groups, analyzing travel itineraries and their interactions with each other, including how close they sat together on the plane. Genome sequencing indicated a single source of COVID-19 spread the disease among the passengers, who came from elsewhere in Europe and two other, unspecified, continents.
The researchers found that the plausible attack rate was 17.8%, with 8 people contracting COVID-19 during the 7.5-hour flight, 3 incubating or infected after the flight, and 1 a tertiary contact of a flight case. At a minimum, the researchers determined, the virus attack rate was 9.8% if 4 of the passengers—those from the more isolated groups—contracted COVID-19 in-flight. They calculated the maximum attack rate to be 25%.
The airline practiced physical distancing and restricted crew and passenger interaction, and of the 13 known people who tested positive, 9 wore masks, 3 had unknown mask statuses, and 1 child did not wear a mask. The outbreak probe closed 28 days after the last symptom onset. Four people had to be hospitalized, with 1 needing intensive care. No deaths were reported.
To prevent future outbreaks linked to flights, the researchers recommend accessing flight manifests quickly, tracking not only flight information but transit information, and ensuring current contact information, as 11 passengers could not be reached.
Oct 23 Eurosurveillance study