Concerns on Close Contacts of Mild Illness or Even Asymptomatic Infections With Different Infectious Capacity

AbstractBackgroundPrevious studies have showed clinical characteristics of patients with the 2019 novel coronavirus disease (COVID-19) and the evidence of person-to-person transmission. Limited data are available for asymptomatic infections. This study aims to present the clinical characteristics of 24 cases with asymptomatic infection screened from close contacts and to show the transmission potential of asymptomatic COVID-19 virus carriers.MethodsEpidemiological investigations were conducted among all close contacts of COVID-19 patients (or suspected patients) in Nanjing, Jiangsu Province, China, from Jan 28 to Feb 9, 2020, both in clinic and in community. Asymptomatic carriers were laboratory-confirmed positive for the COVID-19 virus by testing the nucleic acid of the pharyngeal swab samples. Their clinical records, laboratory assessments, and chest CT scans were reviewed.FindingsNone of the 24 asymptomatic cases presented any obvious symptoms before nucleic acid screening. Five cases (20.8%) developed symptoms (fever, cough, fatigue, etc.) during hospitalization. Twelve (50.0%) cases showed typical CT images of ground-glass chest and 5 (20.8%) presented stripe shadowing in the lungs. The remaining 7 (29.2%) cases showed normal CT image and had no symptoms during hospitalization. These 7 cases were younger (median age: 14.0 years; P = 0.012) than the rest. None of the 24 cases developed severe COVID-19 pneumonia or died. The median communicable period, defined as the interval from the first day of positive nucleic acid tests to the first day of continuous negative tests, was 9.5 days (up to 21 days among the 24 asymptomatic cases). Through epidemiological investigation, we observed a typical asymptomatic transmission to the cohabiting family members, which even caused severe COVID-19 pneumonia.InterpretationThe asymptomatic carriers identified from close contacts were prone to be mildly ill during hospitalization. However, the communicable period could be up to three weeks and the communicated patients could develop severe illness. These results highlighted the importance of close contact tracing and longitudinally surveillance via virus nucleic acid tests. Further isolation recommendation and continuous nucleic acid tests may also be recommended to the patients discharged.

Download Full-text

Asymptomatic low-density Plasmodium infection during non-transmission season: a community-based cross-sectional study in two districts of North Eastern Region, India

Transactions of the Royal Society of Tropical Medicine and Hygiene ◽

10.1093/trstmh/trab017 ◽

2021 ◽

Author(s):

Hari Shankar ◽

Sobhan Phookan ◽

Mrigendra Pal Singh ◽

Ram Suresh Bharti ◽

Naseem Ahmed ◽

...

Keyword(s):

Cross Sectional Study ◽

Diagnostic Tools ◽

Eastern Region ◽

Low Density ◽

Plasmodium Infection ◽

Sectional Study ◽

Cross Sectional ◽

Health Agencies ◽

North Eastern ◽

Asymptomatic Infections

Abstract Background Malaria elimination requires targeting asymptomatic and low-density Plasmodium infections that largely remain undetected. Therefore we conducted a cross-sectional study to estimate the burden of asymptomatic and low-density Plasmodium infection using conventional and molecular diagnostics. Methods A total of 9118 participants, irrespective of age and sex, were screened for malaria using rapid diagnostic tests (RDTs), microscopy and polymerase chain reaction. Results Among the participants, 707 presented with symptoms and 8411 without symptoms, of which Plasmodium was present in 15.6% (110/707) and 8.1% (681/8411), respectively. Low-density infection was found in 5.1% (145/2818) of participants and 8327 of 9118 were Plasmodium negative. Endemicity was propotional to asymptomatic infections (high endemicity 11.1% [404/3633] vs low endemicity 5.8% [277/4778]; odds ratio [OR] 2.0 [95% confidence interval {CI} 1.7 to 2.4]) but inversely related to low-density infection (high endemicity 3.7% [57/1545] vs low endemicity 6.9% [88/1273]; OR 1.9 [95% CI 1.4 to 2.7]). The spleen rate in children 2–9 y of age was 17.9% (602/3368) and the enlarged spleen index was 1.6. Children between 8 and 14 y showed higher odds for asymptomatic (adjusted OR [aOR] 1.75 [95% CI 1.4 to 2.2]) and low-density infections (aOR 0.63 [95% CI 0.4 to 1.0)] than adults. Conclusions The prevalence of asymptomatic and low-density Plasmodium infection undermines the usefulness of standard diagnostic tools used by health agencies. This necessitates deploying molecular tools in areas where malaria microscopy/RDTs indicate a dearth of infection.

Download Full-text

COVID-19 vaccines that reduce symptoms but do not block infection need higher coverage and faster rollout to achieve population impact

Scientific Reports ◽

10.1038/s41598-021-94719-y ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

David A. Swan ◽

Chloe Bracis ◽

Holly Janes ◽

Mia Moore ◽

Laura Matrajt ◽

...

Keyword(s):

Mathematical Model ◽

No Reduction ◽

King County ◽

Symptomatic Disease ◽

Population Impact ◽

Susceptibility To Infection ◽

Infection Susceptibility ◽

Asymptomatic Infections ◽

The U.S

AbstractTrial results for two COVID-19 vaccines suggest at least 90% efficacy against symptomatic disease (VEDIS). It remains unknown whether this efficacy is mediated by lowering SARS-CoV-2 infection susceptibility (VESUSC) or development of symptoms after infection (VESYMP). We aim to assess and compare the population impact of vaccines with different efficacy profiles (VESYMP and VESUSC) satisfying licensure criteria. We developed a mathematical model of SARS-CoV-2 transmission, calibrated to data from King County, Washington. Rollout scenarios starting December 2020 were simulated with combinations of VESUSC and VESYMP resulting in up to 100% VEDIS. We assumed no reduction of infectivity upon infection conditional on presence of symptoms. Proportions of cumulative infections, hospitalizations and deaths prevented over 1 year from vaccination start are reported. Rollouts of 1 M vaccinations (5000 daily) using vaccines with 50% VEDIS are projected to prevent 23–46% of infections and 31–46% of deaths over 1 year. In comparison, vaccines with 90% VEDIS are projected to prevent 37–64% of infections and 46–64% of deaths over 1 year. In both cases, there is a greater reduction if VEDIS is mediated mostly by VESUSC. The use of a “symptom reducing” vaccine will require twice as many people vaccinated than a “susceptibility reducing” vaccine with the same 90% VEDIS to prevent 50% of the infections and death over 1 year. Delaying the start of the vaccination by 3 months decreases the expected population impact by more than 50%. Vaccines which prevent COVID-19 disease but not SARS-CoV-2 infection, and thereby shift symptomatic infections to asymptomatic infections, will prevent fewer infections and require larger and faster vaccination rollouts to have population impact, compared to vaccines that reduce susceptibility to infection. If uncontrolled transmission across the U.S. continues, then expected vaccination in Spring 2021 will provide only limited benefit.

Download Full-text

Genotyping cognate Plasmodium falciparum in humans and mosquitoes to estimate onward transmission of asymptomatic infections

Nature Communications ◽

10.1038/s41467-021-21269-2 ◽

2021 ◽

Vol 12 (1) ◽

Cited By ~ 2

Author(s):

Kelsey M. Sumner ◽

Elizabeth Freedman ◽

Lucy Abel ◽

Andrew Obala ◽

Brian W. Pence ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Odds Ratio ◽

Asymptomatic Malaria ◽

Major Contributor ◽

Western Kenya ◽

High Transmission ◽

Transmission Reduction ◽

Asymptomatic Infections ◽

Infection Types ◽

Natural Settings

AbstractMalaria control may be enhanced by targeting reservoirs of Plasmodium falciparum transmission. One putative reservoir is asymptomatic malaria infections and the scale of their contribution to transmission in natural settings is not known. We assess the contribution of asymptomatic malaria to onward transmission using a 14-month longitudinal cohort of 239 participants in a high transmission site in Western Kenya. We identify P. falciparum in asymptomatically- and symptomatically-infected participants and naturally-fed mosquitoes from their households, genotype all parasites using deep sequencing of the parasite genes pfama1 and pfcsp, and use haplotypes to infer participant-to-mosquito transmission through a probabilistic model. In 1,242 infections (1,039 in people and 203 in mosquitoes), we observe 229 (pfcsp) and 348 (pfama1) unique parasite haplotypes. Using these to link human and mosquito infections, compared with symptomatic infections, asymptomatic infections more than double the odds of transmission to a mosquito among people with both infection types (Odds Ratio: 2.56; 95% Confidence Interval (CI): 1.36–4.81) and among all participants (OR 2.66; 95% CI: 2.05–3.47). Overall, 94.6% (95% CI: 93.1–95.8%) of mosquito infections likely resulted from asymptomatic infections. In high transmission areas, asymptomatic infections are the major contributor to mosquito infections and may be targeted as a component of transmission reduction.

Download Full-text

Assessing testing strategies and duration of quarantine in contact tracing for SARS-CoV-2: a retrospective study of San Francisco’s COVID-19 contact tracing program, June- August, 2020

Open Forum Infectious Diseases ◽

10.1093/ofid/ofab171 ◽

2021 ◽

Author(s):

M J A Reid ◽

P Prado ◽

H Brosnan ◽

A Ernst ◽

H Spindler ◽

...

Keyword(s):

Retrospective Study ◽

San Francisco ◽

Contact Tracing ◽

Testing Strategies ◽

Close Contacts

Abstract We sought to assess the proportion of elicited close contacts diagnosed with COVID-19 at the start, and before exiting quarantine, in San Francisco, USA. From June 8th to August 31st, 6946 contacts were identified; 3008 (46.3%) tested, 940 (13.5%) tested positive; 90% tested positive in first 9 days of quarantine.

Download Full-text

Face Covered and Six Feet Apart: Behavioral Awareness Predicts Greater Adherence to Public Health Guidelines during the COVID-19 Pandemic

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18168247 ◽

2021 ◽

Vol 18 (16) ◽

pp. 8247

Author(s):

Alyssa Schneider ◽

Emily B. Kroska

Keyword(s):

Public Health ◽

Psychological Flexibility ◽

The United States ◽

Future Research ◽

Physical And Mental Health ◽

Logistic Regression Models ◽

Demographic Correlates ◽

Amazon's Mechanical Turk ◽

Predictors Of Adherence ◽

Close Contacts

The COVID-19 pandemic has deleteriously impacted physical and mental health. Guidelines to limit the spread of COVID-19 include wearing a face covering in public, limiting close contacts, and physical distancing. In combatting this and future pandemics, it is essential to understand predictors of adherence, such as psychological flexibility. We hypothesized higher psychological flexibility would relate to greater adherence to public health guidelines. Participants (n = 265) were English-reading/speaking adults in the United States and were recruited through Amazon’s Mechanical Turk. Included in the present analyses are data from June (n = 360) and July 2020 (n = 265). Measures included the Comprehensive Assessment of ACT Processes (CompACT), which measured psychological flexibility. Outcome measures included mask-wearing and number of close contacts, which were operationalized categorically (100% mask-wearing in public, ≤10 close contacts in past week). Two logistic regression models examined psychological flexibility and distress as predictors of adherence to mask-wearing and limiting close contacts, while controlling for demographic correlates. Results indicated that greater behavioral awareness predicted greater odds of mask-wearing and limiting close contacts. Psychological flexibility, and behavioral awareness specifically, should be investigated in future research as targets for intervention amidst global disasters.

Download Full-text

COVID-19 Tracer: Towards Low-cost Passive Close-contacts Searching

2020 International Conference on Internet of Things and Intelligent Applications (ITIA) ◽

10.1109/itia50152.2020.9312302 ◽

2020 ◽

Author(s):

Xu Yang ◽

Peihao Li ◽

Yuqing Yin ◽

Mingzhi Pang ◽

Qiang Niu ◽

...

Keyword(s):

Low Cost ◽

Close Contacts

Download Full-text

Where to go to in chlamydia control? From infection control towards infectious disease control

Sexually Transmitted Infections ◽

10.1136/sextrans-2021-054992 ◽

2021 ◽

pp. sextrans-2021-054992

Author(s):

Jan E A M van Bergen ◽

Bernice Maria Hoenderboom ◽

Silke David ◽

Febe Deug ◽

Janneke C M Heijne ◽

...

Keyword(s):

Chlamydia Infection ◽

Limited Evidence ◽

Future Directions ◽

Tubal Factor Infertility ◽

Effectiveness Analysis ◽

Population Prevalence ◽

Tubal Factor ◽

Health Relevance ◽

Asymptomatic Infections

ObjectivesThe clinical and public health relevance of widespread case finding by testing for asymptomatic chlamydia infections is under debate. We wanted to explore future directions for chlamydia control and generate insights that might guide for evidence-based strategies. In particular, we wanted to know the extent to which we should pursue testing for asymptomatic infections at both genital and extragenital sites.MethodsWe synthesised findings from published literature and from discussions among national and international chlamydia experts during an invitational workshop. We described changing perceptions in chlamydia control to inform the development of recommendations for future avenues for chlamydia control in the Netherlands.ResultsDespite implementing a range of interventions to control chlamydia, there is no practice-based evidence that population prevalence can be reduced by screening programmes or widespread opportunistic testing. There is limited evidence about the beneficial effect of testing on pelvic inflammatory disease prevention. The risk of tubal factor infertility resulting from chlamydia infection is low and evidence on the preventable fraction remains uncertain. Overdiagnosis and overtreatment with antibiotics for self-limiting and non-viable infections have contributed to antimicrobial resistance in other pathogens and may affect oral, anal and genital microbiota. These changing insights could affect the outcome of previous cost–effectiveness analysis.ConclusionThe balance between benefits and harms of widespread testing to detect asymptomatic chlamydia infections is changing. The opinion of our expert group deviates from the existing paradigm of ‘test and treat’ and suggests that future strategies should reduce, rather than expand, the role of widespread testing for asymptomatic chlamydia infections.

Download Full-text