Been too busy to check my promed mails since mid last week.
Here is an interesting report from Switzerland - it appears to have 10.6 undiagnosed cases for every confirmed case
we estimated that for every reported confirmed case, there were 11.6 infections in the community.
Equally interesting is
those older than 65 years (RR, 0.50 [0.28-0.78]) had a significantly lower risk of being seropositive than those aged 20-49 years. Maybe Gnomey can translate that into simple English.
[2] Switzerland (Geneva) serosurvey
Date: Thu 11 Jun 2020
Source: The Lancet [edited]
<https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31304-0/fulltext>
Citation: Stringhini S, Wisniak A, Piumatti G, et al. Seroprevalence
of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland
(SEROCoV-POP): a population-based study. Lancet. Epub 11 Jun 2020.
<https://doi.org/10.1016/S0140-6736(20)31304-0>
Summary
------
Background: Assessing the burden of COVID-19 on the basis of medically
attended case numbers is suboptimal given its reliance on testing
strategy, changing case definitions, and disease presentation.
Population-based serosurveys measuring anti-severe acute respiratory
syndrome coronavirus 2 (anti-SARS-CoV-2) antibodies provide one method
for estimating infection rates and monitoring the progression of the
epidemic. Here, we estimate weekly seroprevalence of anti-SARS-CoV-2
antibodies in the population of Geneva, Switzerland, during the
epidemic.
Methods: The SEROCoV-POP study is a population-based study of former
participants of the Bus Sante study [an annual health examination
survey of a representative sample of the population of the canton] and
their household members. We planned a series of 12 consecutive weekly
serosurveys among randomly selected participants from a previous
population-representative survey, and their household members aged 5
years and older. We tested each participant for anti-SARS-CoV-2-IgG
antibodies using a commercially available ELISA. We estimated
seroprevalence using a Bayesian logistic regression model taking into
account test performance and adjusting for the age and sex of Geneva's
population. Here we present results from the first 5 weeks of the
study.
Findings: Between 6 Apr 2020 and 9 May 2020, we enrolled 2766
participants from 1339 households, with a demographic distribution
similar to that of the canton of Geneva. In the 1st week, we estimated
a seroprevalence of 4.8% (95% CI, 2.4-8.0; n = 341). The estimate
increased to 8.5% (5.9-11.4; n = 469) in the 2nd week, 10.9%
(7.9-14.4; n = 577) in the 3rd week, 6.6% (4.3-9.4; n = 604) in the
4th week, and 10.8% (8.2-13.9; n = 775) in the 5th week. Individuals
aged 5-9 years (relative risk [RR], 0.32 [95% CI, 0.11-0.63]) and
those older than 65 years (RR, 0.50 [0.28-0.78]) had a significantly
lower risk of being seropositive than those aged 20-49 years. After
accounting for the time to seroconversion, we estimated that for every
reported confirmed case, there were 11.6 infections in the community.
Interpretation: These results suggest that most of the population of
Geneva remained uninfected during this wave of the pandemic, despite
the high prevalence of COVID-19 in the region (5000 reported clinical
cases over less than 2.5 months in the population of half a million
people). Assuming that the presence of IgG antibodies is associated
with immunity, these results highlight that the epidemic is far from
coming to an end by means of fewer susceptible people in the
population. Further, a significantly lower seroprevalence was observed
for children aged 5-9 years and adults older than 65 years, compared
with those aged 10-64 years. These results will inform countries
considering the easing of restrictions aimed at curbing transmission.
--
Communicated by:
ProMED-mail
<[email protected]>
[It is interesting to see that the estimated uncaptured rate of the
surveillance system is 11.6 -- so for each reported case there are
11.6 additional infected individuals -- in keeping with the estimated
range of 10 to 20 uncaptured infections per reported case. The survey
population is described as: "The SEROCoV-POP study is a
population-based study of former participants of the Bus Sante study
and their household members. The Bus Sante study is a yearly
representative stratified sample of 500 men and 500 women from the
general population of the canton of Geneva. Eligible individuals were
aged 20-74 years, identified through an annual residential list
established by the local government." -- providing somewhat more
validity to the results as representative of the population of the
Canton of Geneva. Interestingly, there was only one positive child in
the 5- to 9-year-old age-group, in a household where there was a
positive adult case, consistent with the observation of children being
less affected. The authors mentioned that there was household
clustering, but there were 21 (17.1%) that had at least one positive
household member. - Mod.MPP]