An approach to lifting self-isolation for health care workers with prolonged shedding of SARS-CoV-2 RNA.

PURPOSE: According to the European Public Health Authority guidance for ending isolation in the context of COVID-19, a convalescent healthcare worker (HCW) can end their isolation at home and resume work upon clinical improvement and two negative RT-PCR tests from respiratory specimens obtained at 24-h intervals at least 8 days after the onset of symptoms. However, convalescent HCWs may shed SARS-CoV-2 viral RNA for prolonged periods. METHODS: 40 healthy HCWs off work because of ongoing positive RT-PCR results in combined nasopharyngeal (NP) and oropharyngeal (OP) swabs following SARS-CoV-2 infection were invited to participate in this study. These HCWs had been in self-isolation because of a PCR-confirmed SARS-CoV-2 infection. NP and OP swabs as well as a blood sample were collected from each participant. RT-PCR and virus isolation was performed with each swab sample and serum neutralization test as well as two different ELISA tests were performed on all serum samples. RESULTS: No viable virions could be detected in any of 29 nasopharyngeal and 29 oropharyngeal swabs taken from 15 long-time carriers. We found SARSCoV- 2 RNA in 14/29 nasopharyngeal and 10/29 oropharyngeal swabs obtained from screening 15 HCWs with previous COVID-19 up to 55 days after symptom onset. Six (40%) of the 15 initially positive HCWs converted to negative and later reverted to positive again according to their medical records. All but one HCW, a healthy volunteer banned from work, showed the presence of neutralizing antibodies in concomitantly taken blood samples. Late threshold cycle (Ct) values in RT-PCR [mean 37.4; median 37.3; range 30.8-41.7] and the lack of virus growth in cell culture indicate that despite the positive PCR results no infectivity remained. CONCLUSION: We recommend lifting isolation if the RT-PCR Ct-value of a naso- or oropharyngeal swab sample is over 30. Positive results obtained from genes targeted with Ct-values > 30 correspond to non-viable/noninfectious particles that are still detected by RT-PCR. In case of Ct-values lower than 30, a blood sample from the patient should be tested for the presence of neutralizing antibodies. If positive, non-infectiousness can also be assumed.

Prevalence of PCV2 in Austrian and German boars and semen used for artificial insemination.

Since epidemiologically-based science on PCV2 in porcine semen is patchy, we investigated 806 Austrian (A) and German (G) AI boars from five studs, and boars from Austrian farms used for on-farm semen collection, for the presence for IgG/IgM in blood by ELISA (n=754) as well as for PCV2 DNA in semen (n=472) and if positive, also in blood of a few boars by nested PCR and sequencing. A total of 420 boars were tested for both PCV2 in semen and antibodies in blood. Boars were aged between 8 and 82 months at sampling. None of the boars tested positive for IgM but 60.1% did for IgG. PCV2 DNA was detected in 86 (18.2%) semen samples. Minor differences were found between boar populations with respect to the number of antibody positive boars and no differences for DNA in semen. Phylogenetic analysis of 28 sequences revealed a genetic diversity of PCV2 in semen within and between boar populations, with sequences belonging to both PCV2 genotypes 1 and 2. Mean nucleotide sequence identity was 95.7%, with maximum pairwise difference of 8.8%. Boars < or =16 months were tested more frequently positive for IgG (P<0.001) and for PCV2 DNA in semen (P<0.05) than older boars. Of 80 boars tested positive in semen, 34 (42.5%) were antibody negative. A total of 58 semen positive boars with (n=33) and without (n=25) IgG were all tested negative for PCV2 DNA in serum. In conclusion, this study demonstrated the ubiquity of PCV2 in the Austrian and German boar population. Genetically diverse PCV2 can be encountered in boar semen. Shedder boars cannot be detected on the basis of serology. There is an apparent possibility of PCV2 being transmitted through semen.