A new study published yesterday in the New England Journal of Medicine, examining the spread of the SARS-CoV-2 virus among the Icelandic populace (via targeting testing and by open-invitation and random-population screening), found that children under the age of ten had a lower incidence of SARS-CoV-2 infection than adolescents or adults and that females had a lower incidence than males. The researchers also noted that many individuals who tested positive reported having no symptoms (although symptoms almost certainly developed later among some of them). The study was a collaboration between researchers at deCODE genetics, Iceland’s Directorate of Health, and the National University Hospital.
COVID-19 was first diagnosed in Iceland on February 28. Testing, however, had begun a month earlier, on January 31, 2020, with individuals deemed to be at high risk for SARS-CoV-2 infection being targeted. These included mainly persons who were already symptomatic (cough, fever, body aches, and shortness of breath), who were returning to Iceland from regions classified as high risk by the health authorities, or who had been in contact with infected persons.
Roughly 6% of the nation tested
As of April 4, 2020, over 22,000 Icelandic residents had been tested for SARS-CoV-2 or roughly 6% of the entire populace. Of the 9,199 individuals who had been targeted for testing, 1,221 tested positive for SARS-CoV-2 (13.3%). Of the 13,080 individuals tested through population screening, 100 tested positive (0.8%): 87 of the 10,797 (0.8%) individuals who accepted an open invitation for testing and 13 of 2,283 (0.6%) individuals who were invited at random. Most individuals in the targeted-testing group who received positive tests early on in the process had recently travelled internationally, in contrast to those who tested positive later in the study.
The study found that within the targeted-testing group, children under the age of ten were less likely to test positive for SARS-CoV-2 than individuals tens years of age or older (6.7% compared to 13.7%). In the population-screening group, no child under ten tested positive, compared to 0.8% of those ten years of age or older. Furthermore, a smaller percentage of females than males received positive results both in the targeted-testing group (11.0% vs. 16.7%) and in the population-screening group (0.6% vs. 0.9%).
The study suggests that as the proportion of infected individuals identified through population screening did not “change substantially during the screening period,” the containment efforts of the Icelandic authorities proved effective. These efforts include the testing of symptomatic individuals, which began one month before the first confirmed SARS-CoV-2 case in Iceland, along with various social-distancing measures that were imposed roughly two weeks after the first confirmed case. Furthermore, all participants who tested positive for SARS-CoV-2 were required to self-isolate until ten days after their fever had subsided (or until they tested negative), and all persons who were in contact with individuals who tested positive were required to self-quarantine for two weeks.
Assurance and alarm
The researchers note that the prevalence of SARS-CoV-2 infection among persons at high risk for infection and the stability of the infection rate in the general population provide “grist for both assurance and alarm,” as a large portion of those who tested positive reported no symptoms:
“Symptoms were common both in participants who tested positive and in those who tested negative for SARS-CoV-2 in the overall population-screening group. Notably, 43% of the participants who tested positive reported having no symptoms, although symptoms almost certainly developed later in some of them. During the study, the prevalence of symptoms decreased considerably in both testing groups (despite the stability of the SARS-CoV-2 infection rate), probably owing to a general decrease in other respiratory infections, which in turn may have been brought about through measures implemented to decrease the spread of SARS-CoV-2.”
Recently, CEO of DeCODE genetics Kári Stefánsson spoke to Iceland Review and shed light on the spread of the novel coronavirus in Iceland. For further information on the state of the COVID-19 epidemic in Iceland click here.