The Label-Free Detection and Identification of SARS-CoV-2 Using Surface-Enhanced Raman Spectroscopy and Principal Component Analysis.

The World Health Organization (WHO) declared in a May 2023 announcement that the COVID-19 illness is no longer categorized as a Public Health Emergency of International Concern (PHEIC); nevertheless, it is still considered an actual threat to world health, social welfare and economic stability. Consequently, the development of a convenient, reliable and affordable approach for detecting and identifying SARS-CoV-2 and its emerging new variants is crucial. The fingerprint and signal amplification characteristics of surface-enhanced Raman spectroscopy (SERS) could serve as an assay scheme for SARS-CoV-2. Here, we report a machine learning-based label-free SERS technique for the rapid and accurate detection and identification of SARS-CoV-2. The SERS spectra collected from samples of four types of coronaviruses on gold nanoparticles film, fabricated using a Langmuir-Blodgett self-assembly, can provide more spectroscopic signatures of the viruses and exhibit low limits of detection (<100 TCID50/mL or even <10 TCID50/mL). Furthermore, the key Raman bands of the SERS spectra were systematically captured by principal component analysis (PCA), which effectively distinguished SARS-CoV-2 and its variant from other coronaviruses. These results demonstrate that the combined use of SERS technology and PCA analysis has great potential for the rapid analysis and discrimination of multiple viruses and even newly emerging viruses without the need for a virus-specific probe.

A comparative study on the persistence and viability of SARS-CoV-2 wild-type and omicron variant on artificially contaminated surfaces: the role of fomites.

Indirect transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has been investigated but it is still not completely understood. The present study aimed to compare the persistence and viability of the lineage B.1 and omicron BA.1 subvariant in five daily-use materials to evaluate the role of fomites as a possible source of infection. Artificial contamination was performed in the first set of materials, ethylene vinyl acetate (EVA), cardboard, polystyrene, aluminium, and plastic. Further surfaces using BA.1 (glass, plexiglass, cotton, polyester, and tetrapak) were conducted. The persistence, viability of Vero E6 cell cultures and the residual infectivity of the two lineages were evaluated over 5 days. The results showed different stabilities between the tested matrices. In cotton and polyester, the RNA was undetectable in 24 and 48h post-contamination (p.c.), respectively, and the virus was not viable within 30 min, while in the other surfaces, both lineages, RNA was detectable until 120h p.c. A rapid decay of the viral load was revealed on cardboard, mostly for the omicron variant. Furthermore, on all the materials, longer stability of BA.1 was demonstrated, but showing a less intense CPE than the wild-type. EVA was the material that was able to better sustain virus stability as the virus developed CPE up to 72h p.c. In conclusion, the potential spread of SARS-CoV-2 through fomites is conceivable, albeit it is difficult to establish the real capacity to infect people. Nevertheless, thise information is fundamental to adopting the appropriate measures to mitigate the spread of SARS-CoV-2 and its variants.

First serological evidence of SARS-CoV-2 natural infection in small ruminants : Brief report.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) emerged in late December 2019 and spread worldwide, quickly becoming a pandemic. This zoonotic coronavirus shows a broad host range, including wildlife and domestic animals. Small ruminants are shown to be susceptible to SARS-CoV-2 but, to date, no natural infection has been reported. Herein, we performed a survey for SARS-CoV-2 among sheep and goats in the Campania region of Italy using an indirect multispecies ELISA. Next, positive sera were submitted to virus serum neutralization for the quantification of specific neutralizing antibodies. Out of 612 sheep and goats, 23 were found ELISA positive (3.75%) and 1 of them showed 1:20 neutralizing antibodies titer. No significant difference was found between the two species, as well as between male and female, geographical location and age. Our findings demonstrate that natural infection can occur in flocks in a field situation. Moreover, low susceptibility to SARS-CoV-2 is reported for sheep and goats, nevertheless, the continuous mutations of this virus open new scenarios on viral host range and tropism, highlighting the importance of investigating animal species that could represent ongoing or future possible hosts.