Frequency, kinetics and determinants of viable SARS-CoV-2 in bioaerosols from ambulatory COVID-19 patients infected with the Beta, Delta or Omicron variants.

Airborne transmission of SARS-CoV-2 aerosol remains contentious. Importantly, whether cough or breath-generated bioaerosols can harbor viable and replicating virus remains largely unclarified. We performed size-fractionated aerosol sampling (Andersen cascade impactor) and evaluated viral culturability in human cell lines (infectiousness), viral genetics, and host immunity in ambulatory participants with COVID-19. Sixty-one percent (27/44) and 50% (22/44) of participants emitted variant-specific culture-positive aerosols <10µm and <5µm, respectively, for up to 9 days after symptom onset. Aerosol culturability is significantly associated with lower neutralizing antibody titers, and suppression of transcriptomic pathways related to innate immunity and the humoral response. A nasopharyngeal Ct <17 rules-in ~40% of aerosol culture-positives and identifies those who are probably highly infectious. A parsimonious three transcript blood-based biosignature is highly predictive of infectious aerosol generation (PPV > 95%). There is considerable heterogeneity in potential infectiousness i.e., only 29% of participants were probably highly infectious (produced culture-positive aerosols <5µm at ~6 days after symptom onset). These data, which comprehensively confirm variant-specific culturable SARS-CoV-2 in aerosol, inform the targeting of transmission-related interventions and public health containment strategies emphasizing improved ventilation.

Diagnosis of COVID-19: Considerations, controversies and challenges.

Coronavirus disease 2019 (COVID-19) due to a novel virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic that has resulted in over 1.5 million confirmed cases and close to 100 000 deaths. In the majority of symptomatic cases, COVID-19 results in a mild disease predominantly characterised by upper respiratory tract symptoms. Reverse transcription polymerase chain reaction (RT-PCR) using a nasopharyngeal sample is the mainstay of diagnosis, but there is an ~30% false negative rate early in the disease and in patients with mild disease, and therefore repeat testing may be required. RT-PCR positivity can persist for several days after resolution of symptoms. IgM and IgG antibody responses become positive several days after the onset of symptoms, and robust antibody responses are detectable in the second week of illness. Antibody-based immunoassays have a limited role in the diagnosis of early symptomatic disease. However, their incremental benefit over RT-PCR in the first 2 weeks of illness is currently being clarified in ongoing studies. Such assays may be useful for surveillance purposes. However, their role in potentially selecting individuals who may benefit from vaccination, or as a biomarker identifying persons who could be redeployed into essential employment roles, is being investigated. Rapid antibody-based immunoassays that detect viral antigen in nasopharyngeal samples are being developed and evaluated.

Outcomes of outpatient ureteral stenting without fluoroscopy at Groote Schuur Hospital, Cape Town, South Africa.

BACKGROUND: Ureteral stenting is generally a theatre-based procedure that requires a multidisciplinary team and on-table imaging. Limited hospital bed numbers and theatre time in our centre in Cape Town, South Africa, have led us to explore an alternative approach. OBJECTIVES: To see whether outpatient insertion of ureteric stents under local anaesthesia without fluoroscopy was a possible and acceptable alternative to theatre-based ureteral stenting. METHODS: Ureteral stenting (double-J stents and ureteric catheters) was performed with flexible cystoscopy under local anaesthesia and chemoprophylaxis, but without fluoroscopic guidance, in an outpatient setting. Every patient had an abdominal radiograph and an ultrasound scan of the kidney after the procedure to confirm stent position. RESULTS: Three hundred and sixteen procedures (276 double-J stents and 40 ureteric catheters) were performed in 161 men and 155 women. The overall success rate for the procedures was 85.4%, independent of gender (p=0.87), age (p=0.13), type of device inserted (p=0.81) or unilateral/bilateral nature of the procedure (p=1.0). Procedures with a successful outcome were performed in a significantly (p<0.0001) shorter median time (10 minutes (interquartile range (IQR) 5 - 15)) than failed procedures (20 minutes (IQR 10 - 30)). Patients with a pain score of >5 experienced a significantly (p=0.02) greater proportion of failure (27.3%) than patients with a pain score of ≤5 (12.5%). Difficulties were encountered in 23.7% of procedures, with a significantly higher proportion being registered in failed interventions compared with successful ones (82.6% v. 13.7%; p<0.0001). CONCLUSIONS: The procedure was easily mastered and technically simple, and represents savings in cost, time and human resources in our setting.

CD4 T cell depletion at the cervix during HIV infection is associated with accumulation of terminally differentiated T cells.

In blood, the accumulation of terminally differentiated (TD) T cells during HIV infection is associated with CD4 T cell loss and HIV disease progression. Here, we investigated the maintenance and functional characteristics of memory T cells at the cervix. We found that CD4 T cell depletion at the cervix mirrors CD4 depletion in blood. In all women, depletion of CD4 T cells at the cervix was associated with significant reductions in CD45RA- CCR7+ (central memory [CM]) T cells and the accumulation of CD45RA+ CCR7- (TD T cells). We determined whether inflammation in the genital tract was associated with the local differentiation of T cells at the cervix. In uninfected women, genital tract inflammation was associated with the accumulation of CD45RA- CCR7+ CM CD4 T cells and reduced frequencies of CD45RA+ CCR7- TD cells at the cervix. This finding may reflect the fact that, in the absence of HIV infection, TD T cells may be slowly lost in the presence of genital inflammation, while CD45RA- CCR7+ CM T cells are recruited to replenish the diminishing CD4 T cell pool. Following global stimulation with phorbol myristate acetate (PMA)-ionomycin, we noted a significant interleukin 2 (IL-2) deficit in both cervical and blood CD4 T cells from HIV-infected women compared to uninfected women, while gamma interferon (IFN-γ) production was similar, irrespective of HIV status. Few HIV-infected women had detectable IFN-γ and IL-2 HIV-specific T cell responses at the cervix, and these responses were significantly lower in magnitude than the corresponding responses in blood. These data suggest that CD4 depletion was associated with the accumulation of terminally differentiated T cell phenotypes at the cervical mucosa defective in their ability to produce IL-2. CD4 depletion and compromised immunity at the cervix may be accompanied by progressive decline of central memory-like T cells and development of T cells toward terminally differentiated phenotypes.