Viral Cultures for Assessing Fomite Transmission of SARS-CoV-2: a Systematic Review and Meta-Analysis.

INTRODUCTION: The role of fomites in the transmission of SARS-CoV-2 is unclear. Our objective was to assess whether SARS-CoV-2 can be transmitted through fomites, using evidence from viral culture studies. METHODS: We conducted searches in the WHO Covid-19 Database, PubMed, LitCovid, medRxiv, and Google Scholar to 31 December 2021. We included studies that investigated fomite transmission and performed viral culture to assess the cytopathic effect (CPE) of positive fomite samples and confirmation of SARS-CoV-2 as the cause of the CPE. We assessed the risk of bias using a checklist modified from the QUADAS-2 criteria. RESULTS: We included 23 studies. The overall risk of bias was moderate. Five studies demonstrated replication-competent virus from fomite cultures and three used genome sequencing to match fomite samples with human clinical specimens. The mean Ct of samples with positive viral culture was significantly lower compared with cultured samples that returned negative results: SMD -1.45, 95%CI -2.00 to -0.90, I2=0%; P<0.00001. The likelihood of isolating replication-competent virus was significantly greater when the Ct was <30: RR 3.10 (95%CI 1.32 to 7.31, I2=71%, P=0.01). Infectious specimens were mostly detected within 7 days of symptom onset. One study showed possible transmission of SARS-CoV-2 from fomites to humans. CONCLUSION: The evidence from published studies suggests that replication-competent SARS-CoV-2 is present on fomites. Replication-competent SARS-CoV-2 is significantly more likely when the PCR Ct for clinical specimens and fomite samples is <30. Further studies should investigate the duration of infectiousness of SARS-CoV-2 and the frequency of transmission from fomites.