Geneva: Seroprevalence up 3% per week

Geneva University Hospital results capture an epidemic in motion

A fascinating weekly serosurvey by researchers at Geneva University Hospital (HUG) and the University of Geneva has managed to capture seroconversion in progress.

Geneva, like all Switzerland, was put under lock-down in mid-March. HUG began taking blood samples from a random sample of 1330 from approximately 600 households each week in early April. The weekly results as of 6 May, 2020:

• 1st week 3.1% — April 6
• 2nd week 6.1% — April 13
• 3rd week 9.7% — April 20

Conservatively assuming a delay of 4 weeks from date of infection to seroconversion, if the mid-March lock-down worked to stop new infections, that rapid increase should slow down or stop in the next reporting week.

HUG has a large database of 10,000+ patients who participated in the something called the Bus Santé study (an annual health examination). For the weekly serosurveys, HUG draws a new random sample of 1,330 from that universe and invites them and their family members, including children older than 5, to participate. Those in quarantine or isolation or with symptoms as of the date of the invitation are excluded.

A few other findings of interest:

  • no differences in seroprevalence between children and middle age adults.
  • roughly 10 infections for every COVID-19 confirmed case in Geneva, “reflecting the variability in disease severity, testing practices and care-seeking behaviors.”

In a different study, around 3% of medical staff in Switzerland have been infected with Covid-19, based on data covering the period up until Easter, according to Switzerland’s Federal Office of Public Health.

You can follow the COVID aB Tracking blog on Twitter @Will_Bates_sci

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