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1.
Intern Med ; 61(2): 159-165, 2022 Jan 15.
Article in English | MEDLINE | ID: covidwho-1622449

ABSTRACT

Objective To examine the continuation of antibody prevalence and background factors in antibody-positive subjects after asymptomatic infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods A study was carried out to investigate the SARS-CoV-2 antibody (IgG) prevalence. SARS-CoV-2 antibodies (IgG) were measured and analyzed with immunochromatographic tests. Patients Among 1,603 subjects, comprising patients, physicians, and nurses at 65 medical institutes in Kanagawa, Japan, 39 antibody-positive subjects received follow-up for 6 months. Results Of the 33 subjects who consented to the follow-up (23 patients and 10 medical professionals), continued positivity of IgG antibodies was confirmed in 11 of 32 cases (34.4%) after 2 months, 8 of 33 (24.2%) after 4 months, and 8 of 33 (24.2%) after 6 months. A significant difference was found in the sleeping time, drinking habits, hypertension, and use of angiotensin-receptor blockers on comparing subject background characteristics among three groups: patients with antibody production that continued for six months after the first detection of positivity, patients in whom antibody production stopped at four months, and patients in whom antibody production stopped at two months. Conclusion The continuation rate of IgG antibody prevalence was 24.2% at 6 months after the first detection of antibody positivity in cases with asymptomatic coronavirus disease 2019 (COVID-19) infections. This percentage is low compared with the antibody continuation rate in patients who have recovered from symptomatic COVID-19 infection.


Subject(s)
COVID-19 , Antibodies, Viral , Humans , Immunoglobulin G , Immunoglobulin M , Prevalence , SARS-CoV-2
2.
Public Health Action ; 11(2): 58-60, 2021 Jun 21.
Article in English | MEDLINE | ID: covidwho-1278665

ABSTRACT

Asymptomatic COVID-19 may contribute significantly to the pandemic trajectory based on global biological, epidemiological and modelling evidence. A retrospective analysis was done to determine the proportion of asymptomatic COVID-19 in the workplace during the lockdown period from 27 March to 31 May 2020. We found that nearly 45% of cases were asymptomatic at the time of the first test. This high proportion of asymptomatic COVID-19 cases has implications for interventions, such as enforcing quarantine of all close contacts of COVID-19 cases regardless of symptoms.


Le COVID-19 a symptomatique pourrait contribuer significativement à la trajectoire de la pandémie en se basant sur des preuves mondiales, biologique et épidémiologiques, et en modélisant les preuves. Une analyse rétrospective a été réalisée afin de décrire la proportion d'infections asymptomatiques de SARS-CoV-2 parmi les clusters essentiels sur les lieux de travail en Afrique du Sud où des investigations de flambée ont été réalisées durant la période de confinement très restrictive du 27 mars au 31 mai 2020. Près de 45% des cas étaient asymptomatique lors du premier test. Cette proportion élevée des cas de COVID-19 asymptomatiques a des implications en ce qui concerne les interventions nonpharmaceutique comme le renforcement de la quarantaine de tous les contacts étroits des cas de SARS-CoV-2 sans tenir compte des symptômes.

3.
Int J Infect Dis ; 105: 236-238, 2021 Apr.
Article in English | MEDLINE | ID: covidwho-1093059

ABSTRACT

BACKGROUND: The epidemiological importance of asymptomatic individuals who would never develop illness, compared to those who eventually develop symptoms, has yet to be fully clarified. METHODS: The very first cluster data in Tokyo and Kanagawa (n = 36) were analyzed. Movement of all close contact was restricted for 14 days and they underwent laboratory testing with polymerase chain reaction. The reproduction numbers of symptomatic and asymptomatic cases were estimated. RESULTS: The reproduction number for symptomatic cases was estimated to be 1.2 (95% confidence interval (CI): 0.5-2.9). The relative infectiousness of asymptomatically infected cases was estimated to be 0.27 (95% CI: 0.03-0.81) of symptomatic cases. CONCLUSION: The relative transmissibility of asymptomatic cases is limited. Observing clusters starting with symptomatic transmission might be sufficient for the control.


Subject(s)
Asymptomatic Infections , COVID-19/transmission , SARS-CoV-2 , Basic Reproduction Number , Female , Humans , Japan/epidemiology , Male , Middle Aged
4.
J Infect Chemother ; 26(12): 1294-1300, 2020 Dec.
Article in English | MEDLINE | ID: covidwho-744123

ABSTRACT

OBJECTIVES: We investigated relationships between subclinical COVID-19 (coronavirus disease 2019) and background factors. METHODS: We determined SARS-CoV-2 antibody (IgG) prevalence in 1603 patients, doctors, and nurses in 65 medical institutions in Kanagawa Prefecture, Japan and investigated their background factors. Antibodies (IgG) against SARS-CoV-2 were analyzed by Immunochromatographic test. RESULTS: The 39 subjects (2.4%) were found to be IgG antibody-positive: 29 in the patient group (2.9%), 10 in the doctor/nurse group (2.0%), and 0 in the control group. After adjustment for age, sex, and the antibody prevalence in the control group, antibody prevalence was 2.7% in the patient group and 2.1% in the doctor/nurse group. There was no significant difference between the antibody-positive subjects and the antibody-negative subjects in any background factors investigated including overseas travel, contact with overseas travelers, presence/absence of infected individuals in the living area, use of trains 5 times a week or more, BCG vaccination, and use of ACE inhibitor and ARB. CONCLUSIONS: Antibody prevalence in the present survey at medical institution is higher than that in Tokyo and in Osaka measured by the government suggesting that subclinical infections are occurring more frequently than expected. No background factor that influenced antibody-positive status due to subclinical infection was identified.


Subject(s)
Asymptomatic Infections/epidemiology , Betacoronavirus/immunology , Coronavirus Infections/epidemiology , Pneumonia, Viral/epidemiology , Adult , Aged , Antibodies, Viral/isolation & purification , COVID-19 , Chromatography, Affinity , Coronavirus Infections/immunology , Female , Humans , Immunoglobulin G/isolation & purification , Japan/epidemiology , Male , Middle Aged , Pandemics , Pneumonia, Viral/immunology , SARS-CoV-2 , Surveys and Questionnaires
5.
Am J Kidney Dis ; 76(4): 490-499.e1, 2020 10.
Article in English | MEDLINE | ID: covidwho-730121

ABSTRACT

RATIONALE & OBJECTIVE: Patients receiving maintenance hemodialysis (MHD) are highly vulnerable to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The current study was designed to evaluate the prevalence of SARS-CoV-2 infection based on both nucleic acid testing (NAT) and antibody testing in Chinese patients receiving MHD. STUDY DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: From December 1, 2019, to March 31, 2020, a total of 1,027 MHD patients in 5 large hemodialysis centers in Wuhan, China, were enrolled. Patients were screened for SARS-CoV-2 infection by symptoms and initial computed tomography (CT) of the chest. If patients developed symptoms after the initial screening was negative, repeat CT was performed. Patients suspected of being infected with SARS-CoV-2 were tested with 2 consecutive throat swabs for viral RNA. In mid-March 2020, antibody testing for SARS-CoV-2 was obtained for all MHD patients. EXPOSURE: NAT and antibody testing results for SARS-CoV-2. OUTCOMES: Morbidity, clinical features, and laboratory and radiologic findings. ANALYTICAL APPROACH: Differences between groups were examined using t test or Mann-Whitney U test, comparing those not infected with those infected and comparing those with infection detected using NAT with those with infection detected by positive serology test results. RESULTS: Among 1,027 patients receiving MHD, 99 were identified as having SARS-CoV-2 infection, for a prevalence of 9.6%. Among the 99 cases, 52 (53%) were initially diagnosed with SARS-CoV-2 infection by positive NAT; 47 (47%) were identified later by positive immunoglobulin G (IgG) or IgM antibodies against SARS-CoV-2. There was a spectrum of antibody profiles in these 47 patients: IgM antibodies in 5 (11%), IgG antibodies in 35 (74%), and both IgM and IgG antibodies in 7 (15%). Of the 99 cases, 51% were asymptomatic during the epidemic; 61% had ground-glass or patchy opacities on CT of the chest compared with 11.6% among uninfected patients (P<0.001). Patients with hypertensive kidney disease were more often found to have SARS-CoV-2 infection and were more likely to be symptomatic than patients with another primary cause of kidney failure. LIMITATIONS: Possible false-positive and false-negative results for both NAT and antibody testing; possible lack of generalizability to other dialysis populations. CONCLUSIONS: Half the SARS-CoV-2 infections in patients receiving MHD were subclinical and were not identified by universal CT of the chest and selective NAT. Serologic testing may help evaluate the overall prevalence and understand the diversity of clinical courses among patients receiving MHD who are infected with SARS-CoV-2.


Subject(s)
Antibodies, Viral/analysis , Betacoronavirus/immunology , Coronavirus Infections/diagnosis , Kidney Failure, Chronic/therapy , Pneumonia, Viral/diagnosis , Renal Dialysis , COVID-19 , China/epidemiology , Comorbidity , Coronavirus Infections/epidemiology , Cross-Sectional Studies , Female , Humans , Kidney Failure, Chronic/epidemiology , Male , Middle Aged , Pandemics , Pneumonia, Viral/epidemiology , Prevalence , Retrospective Studies , SARS-CoV-2 , Serologic Tests/methods , Tomography, X-Ray Computed
6.
Contemp Clin Trials ; 96: 106101, 2020 09.
Article in English | MEDLINE | ID: covidwho-696835

ABSTRACT

The control strategies preventing subclinical transmission differed among countries. A stochastic transmission model was used to assess the potential effectiveness of control strategies at controlling the COVID-19 outbreak. Three strategies included lack of prevention of subclinical transmission (Strategy A), partial prevention using testing with different accuracy (Strategy B) and complete prevention by isolating all at-risk people (Strategy C, Taiwan policy). The high probability of containing COVID-19 in Strategy C is observed in different scenario, had varied in the number of initial cases (5, 20, and 40), the reproduction number (1.5, 2, 2.5, and 3.5), the proportion of at-risk people being investigated (40%, 60%, 80%, to 90%), the delay from symptom onset to isolation (long and short), and the proportion of transmission that occurred before symptom onset (<1%, 15%, and 30%). Strategy C achieved probability of 80% under advantageous scenario, such as low number of initial cases and high coverage of epidemiological investigation but Strategy B and C rarely achieved that of 60%. Considering the unsatisfactory accuracy of current testing and insufficient resources, isolation of all at-risk people, as adopted in Taiwan, could be an effective alternative.


Subject(s)
Asymptomatic Infections/epidemiology , Communicable Disease Control , Coronavirus Infections/epidemiology , Coronavirus Infections/transmission , Pneumonia, Viral/epidemiology , Pneumonia, Viral/transmission , Betacoronavirus , COVID-19 , Coronavirus Infections/prevention & control , Humans , Infectious Disease Incubation Period , Models, Theoretical , Pandemics/prevention & control , Patient Isolation , Pneumonia, Viral/prevention & control , Quarantine , SARS-CoV-2 , Taiwan/epidemiology
7.
Innovation (N Y) ; 1(2): 100026, 2020 Aug 28.
Article in English | MEDLINE | ID: covidwho-693467

ABSTRACT

Recently, considerable efforts have been focused on intensifying the screening process for asymptomatic COVID-19 cases in the Chinese Mainland, especially for up to 10 million citizens living in Wuhan City by nucleic acid testing. However, a high percentage of domestic asymptomatic cases did not develop into symptomatic ones, which is abnormal and has drawn considerable public attention. Here, we aimed to investigate the prevalence of COVID-19 infections in the Chinese Mainland from a statistical perspective, as it is of referential significance for other regions. By conservatively assuming a development time lag from pre-symptomatic (i.e., referring to the infected cases that were screened before the COVID-19 symptom onset) to symptomatic as an incubation time of 5.2 days, our results indicated that 92.5% of those tested in Wuhan City, China, and 95.1% of those tested in the Chinese Mainland should have COVID-19 syndrome onset, which was extremely higher than their corresponding practical percentages of 0.8% and 3.3%, respectively. We propose that a certain false positive rate may exist if large-scale nucleic acid screening tests for asymptomatic cases are conducted in common communities with a low incidence rate. Despite adopting relatively high-sensitivity, high-specificity detection kits, we estimated a very low prevalence of COVID-19 infections, ranging from 10-6 to 10-4 in both Wuhan City and the Chinese Mainland. Thus, the prevalence rate of asymptomatic infections in China had been at a very low level. Furthermore, given the lower prevalence of the infection, close examination of the data for false positive results is necessary to minimize social and economic impacts.

8.
Eur J Cancer ; 135: 101-102, 2020 08.
Article in English | MEDLINE | ID: covidwho-458966

ABSTRACT

Subclinical COVID-19 subjects pose a significant challenge. We present a very close clinical interaction with a subclinical COVID-19 subject that met the "standard screening criteria" and is unique in several ways. Learning from our experience, we suggest close attention should be paid to any unexpected findings such as groundglass opacity on CT as it could help early identification of subclinical COVID-19 infection.


Subject(s)
Asymptomatic Infections , Betacoronavirus/isolation & purification , Breast Neoplasms/therapy , Coronavirus Infections/diagnosis , Infectious Disease Transmission, Patient-to-Professional/prevention & control , Pneumonia, Viral/diagnosis , Betacoronavirus/pathogenicity , Breast/diagnostic imaging , Breast/surgery , Breast Neoplasms/diagnosis , COVID-19 , COVID-19 Testing , Clinical Laboratory Techniques , Coronavirus Infections/prevention & control , Coronavirus Infections/transmission , Coronavirus Infections/virology , Female , Humans , Lung/diagnostic imaging , Mass Screening/standards , Mastectomy , Nasopharynx/virology , Pandemics/prevention & control , Pneumonia, Viral/prevention & control , Pneumonia, Viral/transmission , Pneumonia, Viral/virology , Radiotherapy Planning, Computer-Assisted , Radiotherapy, Adjuvant , SARS-CoV-2 , Tomography, X-Ray Computed
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