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1.
Clin Infect Dis ; 73(9): e2946-e2951, 2021 11 02.
Article in English | MEDLINE | ID: covidwho-1500988

ABSTRACT

BACKGROUND: Waning immunity occurs in patients who have recovered from Coronavirus Disease 2019 (COVID-19). However, it remains unclear whether true re-infection occurs. METHODS: Whole genome sequencing was performed directly on respiratory specimens collected during 2 episodes of COVID-19 in a patient. Comparative genome analysis was conducted to differentiate re-infection from persistent viral shedding. Laboratory results, including RT-PCR Ct values and serum Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) IgG, were analyzed. RESULTS: The second episode of asymptomatic infection occurred 142 days after the first symptomatic episode in an apparently immunocompetent patient. During the second episode, there was evidence of acute infection including elevated C-reactive protein and SARS-CoV-2 IgG seroconversion. Viral genomes from first and second episodes belong to different clades/lineages. The virus genome from the first episode contained a a stop codon at position 64 of ORF8, leading to a truncation of 58 amino acids. Another 23 nucleotide and 13 amino acid differences located in 9 different proteins, including positions of B and T cell epitopes, were found between viruses from the first and second episodes. Compared to viral genomes in GISAID, the first virus genome was phylogenetically closely related to strains collected in March/April 2020, while the second virus genome was closely related to strains collected in July/August 2020. CONCLUSIONS: Epidemiological, clinical, serological, and genomic analyses confirmed that the patient had re-infection instead of persistent viral shedding from first infection. Our results suggest SARS-CoV-2 may continue to circulate among humans despite herd immunity due to natural infection. Further studies of patients with re-infection will shed light on protective immunological correlates for guiding vaccine design.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Genome, Viral , Humans , Reinfection , Whole Genome Sequencing
2.
EBioMedicine ; 71: 103544, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1363987

ABSTRACT

BACKGROUND: Several SARS-CoV-2 lineages with spike receptor binding domain (RBD) N501Y mutation have spread globally. We evaluated the impact of N501Y on neutralizing activity of COVID-19 convalescent sera and on anti-RBD IgG assays. METHODS: The susceptibility to neutralization by COVID-19 patients' convalescent sera from Hong Kong were compared between two SARS-CoV-2 isolates (B117-1/B117-2) from the α variant with N501Y and 4 non-N501Y isolates. The effect of N501Y on antibody binding was assessed. The performance of commercially-available IgG assays was determined for patients infected with N501Y variants. FINDINGS: The microneutralization antibody (MN) titers of convalescent sera from 9 recovered COVID-19 patients against B117-1 (geometric mean titer[GMT],80; 95% CI, 47-136) were similar to those against the non-N501Y viruses. However, MN titer of these serum against B117-2 (GMT, 20; 95% CI, 11-36) was statistically significantly reduced when compared with non-N501Y viruses (P < 0.01; one-way ANOVA). The difference between B117-1 and B117-2 was confirmed by testing 60 additional convalescent sera. B117-1 and B117-2 differ by only 3 amino acids (nsp2-S512Y, nsp13-K460R, spike-A1056V). Enzyme immunoassay using 272 convalescent sera showed reduced binding of anti-RBD IgG to N501Y or N501Y-E484K-K417N when compared with that of wild-type RBD (mean difference: 0.1116 and 0.5613, respectively; one-way ANOVA). Of 7 anti-N-IgG positive sera from patients infected with N501Y variants (collected 9-14 days post symptom onset), 6 (85.7%) tested negative for a commercially-available anti-S1-IgG assay. FUNDING: Richard and Carol Yu, Michael Tong, and the Government Consultancy Service (see acknowledgments for full list). INTERPRETATION: We highlighted the importance of using a panel of viruses within the same lineage to determine the impact of virus variants on neutralization. Furthermore, clinicians should be aware of the potential reduced sensitivity of anti-RBD IgG assays.


Subject(s)
COVID-19/therapy , SARS-CoV-2/genetics , Spike Glycoprotein, Coronavirus/genetics , Adult , Aged , Antibodies, Neutralizing/administration & dosage , Antibodies, Neutralizing/immunology , Antibodies, Viral/administration & dosage , Antibodies, Viral/ultrastructure , COVID-19/genetics , COVID-19/immunology , COVID-19/virology , Female , Humans , Immunization, Passive , Male , Middle Aged , Mutation/genetics , Neutralization Tests , SARS-CoV-2/immunology , SARS-CoV-2/pathogenicity , Spike Glycoprotein, Coronavirus/immunology
3.
Infect Control Hosp Epidemiol ; 43(3): 334-343, 2022 03.
Article in English | MEDLINE | ID: covidwho-1189150

ABSTRACT

BACKGROUND: Nosocomial outbreaks leading to healthcare worker (HCW) infection and death have been increasingly reported during the coronavirus disease 2019 (COVID-19) pandemic. OBJECTIVE: We implemented a strategy to reduce nosocomial acquisition. METHODS: We summarized our experience in implementing a multipronged infection control strategy in the first 300 days (December 31, 2019, to October 25, 2020) of the COVID-19 pandemic under the governance of Hospital Authority in Hong Kong. RESULTS: Of 5,296 COVID-19 patients, 4,808 (90.8%) were diagnosed in the first pandemic wave (142 cases), second wave (896 cases), and third wave (3,770 cases) in Hong Kong. With the exception of 1 patient who died before admission, all COVID-19 patients were admitted to the public healthcare system for a total of 78,834 COVID-19 patient days. The median length of stay was 13 days (range, 1-128). Of 81,955 HCWs, 38 HCWs (0.05%; 2 doctors and 11 nurses and 25 nonprofessional staff) acquired COVID-19. With the exception of 5 of 38 HCWs (13.2%) infected by HCW-to-HCW transmission in the nonclinical settings, no HCW had documented transmission from COVID-19 patients in the hospitals. The incidence of COVID-19 among HCWs was significantly lower than that of our general population (0.46 per 1,000 HCWs vs 0.71 per 1,000 population; P = .008). The incidence of COVID-19 among professional staff was significantly lower than that of nonprofessional staff (0.30 vs 0.66 per 1,000 full-time equivalent; P = .022). CONCLUSIONS: A hospital-based approach spared our healthcare service from being overloaded. With our multipronged infection control strategy, no nosocomial COVID-19 in was identified among HCWs in the first 300 days of the COVID-19 pandemic in Hong Kong.


Subject(s)
COVID-19 , Cross Infection , COVID-19/epidemiology , COVID-19/prevention & control , Cross Infection/epidemiology , Cross Infection/prevention & control , Health Personnel , Hong Kong/epidemiology , Hospitals , Humans , Infection Control , Pandemics/prevention & control
4.
Infect Control Hosp Epidemiol ; 42(9): 1037-1045, 2021 09.
Article in English | MEDLINE | ID: covidwho-962228

ABSTRACT

BACKGROUND: Extensive environmental contamination by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported in hospitals during the coronavirus disease 2019 (COVID-19) pandemic. We report our experience with the practice of directly observed environmental disinfection (DOED) in a community isolation facility (CIF) and a community treatment facility (CTF) in Hong Kong. METHODS: The CIF, with 250 single-room bungalows in a holiday camp, opened on July 24, 2020, to receive step-down patients from hospitals. The CTF, with 500 beds in open cubicles inside a convention hall, was activated on August 1, 2020, to admit newly diagnosed COVID-19 patients from the community. Healthcare workers (HCWs) and cleaning staff received infection control training to reinforce donning and doffing of personal protective equipment and to understand the practice of DOED, in which the cleaning staff observed patient and staff activities and then performed environmental disinfection immediately thereafter. Supervisors also observed cleaning staff to ensure the quality of work. In the CTF, air and environmental samples were collected on days 7, 14, 21, and 28 for SARS-CoV-2 detection by RT-PCR. Patient compliance with mask wearing was also recorded. RESULTS: Of 291 HCWs and 54 cleaning staff who managed 243 patients in the CIF and 674 patients in the CTF from July 24 to August 29, 2020, no one acquired COVID-19. All 24 air samples and 520 environmental samples collected in the patient area of the CTF were negative for SARS-CoV-2. Patient compliance with mask wearing was 100%. CONCLUSION: With appropriate infection control measures, zero environmental contamination and nosocomial transmission of SARS-CoV-2 to HCWs and cleaning staff was achieved.


Subject(s)
COVID-19 , Disinfection , Health Personnel , Humans , Infection Control , Pandemics , Personal Protective Equipment , SARS-CoV-2
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