Abstract
ObjectivesThe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has heavily impacted Italy. The government's restriction measures have attenuated the burden on hospitals. The association of high viral replication with disease severity suggests the potential for lower viral load in milder clinical presentations. MethodsThe reverse-transcription-polymerase-chain-reaction (RT-PCR) profile of 944 consecutive, non-replicate, positive retropharyngeal swabs was collected from 3 March to 8 June 2020 to investigate the temporal profile of SARS-CoV-2 viral load in the region of Capitanata, Apulia. Cycle threshold (Ct) values of 3 targets (N [nucleocapsid protein], E [envelope protein] and RdRP [RNA-dependent RNA-polymerase]) were analysed. ResultsThe median Ct values of the 3 targets increased considerably over the study period, showing a progressive and constant weekly change. The negative detection rate of E and RdRP increased over time. These data suggest that SARS-CoV-2 viral load progressively decreased along the outbreak course. During the first epidemic peak (March and April) the viral load among patients >80-years was significantly higher than for younger subjects. However, in May this age-dependent difference disappeared, underlying viral load reduction in the elderly. ConclusionsAn attenuation of viral transmission or pathogenicity during the epidemic course is suggested, likely due to restriction measures, although viral factors might also be considered.
Highlights
From early 2020 a new Coronavirus disease named COVID-19 has spread worldwide with Italy being one of the most affected countries, albeit with substantial regional differences (IstitutoSuperiorediSanità; WHO)
The number of new COVID-19 infections decreased in Italy after the adoption of restriction measures
A small study conducted in a Lombardy hospital at the end of the first epidemic phase reported that the viral load was significantly reducing (Clementi et al, 2020), results were not transferable due to the small sample size of the study population and the limited period of analysis
Summary
From early 2020 a new Coronavirus disease named COVID-19 has spread worldwide with Italy being one of the most affected countries, albeit with substantial regional differences (IstitutoSuperiorediSanità; WHO). In the Apulia region (southern Italy) approximately 7900 cases of COVID-19 infection have been reported so far, with a peak at the end of April and a substantial decrease from May-June. The rate of hospitalization and number of severe cases fell during this time (IstitutoSuperiorediSanità). The Italian Government's restriction measures have contributed to pandemic control (Prem et al, 2020). Use of personal protective equipment (PPE) and active territorial surveillance may all have reduced SARS-CoV-2 transmission (Chan et al, 2020; Prather et al, 2020; Prem et al, 2020). Viral factors, host-virus interaction, and the summer season are potential contributing factors in the pandemic slowdown.
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