Abstract
ObjectiveThrough a hospital-based SARS-CoV-2 molecular and serological screening, we evaluated the effectiveness of two months of lockdown and two of surveillance, in Milan, Lombardy, the first to be overwhelmed by COVID-19 pandemics during March-April 2020.MethodsAll subjects presenting at the major hospital of Milan from May-11 to July-5, 2020, underwent a serological screening by chemiluminescent assays. Those admitted were further tested by RT-PCR.ResultsThe cumulative anti-N IgG seroprevalence in the 2753 subjects analyzed was of 5.1% (95%CI = 4.3%-6.0%), with a peak of 8.4% (6.1%-11.4%) 60–63 days since the peak of diagnoses (March-20). 31/106 (29.2%) anti-N reactive subjects had anti-S1/S2 titers >80 AU/mL. Being tested from May-18 to June-5, or residing in the provinces with higher SARS-CoV-2 circulation, were positively and independently associated with anti-N IgG reactivity (OR [95%CI]: 2.179[1.455–3.264] and 3.127[1.18–8.29], respectively). In the 18 RT-PCR positive, symptomatic subjects, anti-N seroprevalence was 33.3% (95% CI: 14.8%-56.3%).ConclusionSARS-CoV-2 seroprevalence in Milan is low, and in a downward trend after only 60–63 days since the peak of diagnoses. Italian confinement measures were effective, but the risk of contagion remains concrete. In hospital-settings, the performance of molecular and serological screenings upon admission remains highly advisable.
Highlights
On January 30 2020, the World Health Organization (WHO) classified the ongoing outbreak by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Wuhan province, China, as a Public Health Emergency of International Concern [1]
The cumulative anti-N IgG seroprevalence in the 2753 subjects analyzed was of 5.1% (95%confidence interval (CI) = 4.3%-6.0%), with a peak of 8.4% (6.1%-11.4%) 60–63 days since the peak of diagnoses (March-20). 31/106 (29.2%) anti-N reactive subjects had anti-S1/S2 titers >80 AU/mL
In the 18 RT-PCR positive, symptomatic subjects, anti-N seroprevalence was 33.3%
Summary
On January 30 2020, the World Health Organization (WHO) classified the ongoing outbreak by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Wuhan province, China, as a Public Health Emergency of International Concern [1]. Lombardy was the first region in Europe to be affected by an important contagions’ peak during the month of March, and, still today, it suffers from the highest proportion of population infected (attack rate) among all Italian regions [2]. On March 9th, while the rate of diagnoses was steeply rising, the Italian government decided to shut down all unnecessary activities, and to apply a strict shelter-in-place order. The major COVID19 reference hospital of Milan (Lombardy) started to apply a universal serological and molecular screening for SARS-CoV-2 to all subjects presenting to its Emergency Room (ER), or admitted for any reason
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