-
Scientific Reports Jun 2023Asymptomatic Plasmodium infection raises a problem for the persistent transmission of malaria in low-endemic areas such as Asia. This systematic review was undertaken to... (Meta-Analysis)
Meta-Analysis
Asymptomatic Plasmodium infection raises a problem for the persistent transmission of malaria in low-endemic areas such as Asia. This systematic review was undertaken to estimate the prevalence and proportion of asymptomatic Plasmodium infection in Asia. The systematic review was registered at PROSPERO (ID: CRD42022373664). The research followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A comprehensive search of five databases, Ovid, Scopus, MEDLINE, PubMed, and Embase, was conducted to identify studies of asymptomatic Plasmodium infection in Asian countries. The pooled prevalence of asymptomatic Plasmodium infection, the pooled proportion of asymptomatic Plasmodium infection among all parasitised individuals, and the associated 95% confidence intervals were estimated using a random-effects model. A total of 916 articles were retrieved, and 87 articles that met the criteria were included in the systematic review. The pooled prevalence of asymptomatic Plasmodium infection among enrolled participants in Southeast Asia, South Asia, and Western Asia was 5.8%, 9.4%, and 8.4%, respectively. The pooled proportion of asymptomatic Plasmodium infection among all parasitised individuals in Southeast Asia, South Asia, and Western Asia was 89.3%, 87.2%, and 64.8%, respectively. There was a low prevalence of asymptomatic Plasmodium infection, but there was a high proportion of asymptomatic Plasmodium infection per all parasitised individuals in different parts of Asia. These results may support and facilitate elimination and control programs for asymptomatic Plasmodium infection in Asia.
Topics: Humans; Malaria, Falciparum; Prevalence; Malaria; Plasmodium; Asia; Asymptomatic Infections
PubMed: 37369862
DOI: 10.1038/s41598-023-37439-9 -
International Journal of Environmental... Feb 2023Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection has brought new challenges to the global prevention and control of coronavirus disease 2019... (Meta-Analysis)
Meta-Analysis Review
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection has brought new challenges to the global prevention and control of coronavirus disease 2019 (COVID-19) pandemic; however, current studies suggest that there is still great uncertainty about the risk of severe COVID-19 and poor outcomes after SARS-CoV-2 reinfection. Random-effects inverse-variance models were used to evaluate the pooled prevalence (PP) and its 95% confidence interval (CI) of severity, outcomes and symptoms of reinfection. Random-effects were used to estimate the pooled odds ratios (OR) and its 95%CI of severity and outcomes between reinfections and primary infections. Nineteen studies involving a total of 34,375 cases of SARS-CoV-2 reinfection and 5,264,720 cases of SARS-CoV-2 primary infection were included in this meta-analysis. Among those SARS-CoV-2 reinfection cases, 41.77% (95%CI, 19.23-64.31%) were asymptomatic, and 51.83% (95%CI, 23.90-79.76%) were symptomatic, only 0.58% (95%CI, 0.031-1.14%) manifested as severe illness, and 0.04% (95%CI, 0.009-0.078%) manifested as critical illness. The PPs for SARS-CoV-2 reinfection-related hospitalization, admission to ICU, and death were, respectively, 15.48% (95%CI, 11.98-18.97%), 3.58% (95%CI, 0.39-6.77%), 2.96% (95%CI, 1.25-4.67%). Compared with SARS-CoV-2 primary infection cases, reinfection cases were more likely to present with mild illness (OR = 7.01, 95%CI, 5.83-8.44), and the risk of severe illness was reduced by 86% (OR = 0.14, 95%CI, 0.11-0.16). Primary infection provided some protection against reinfection and reduces the risk of symptomatic infection and severe illness. Reinfection did not contribute to extra risk of hospitalization, ICU, or death. It is suggested to scientifically understand the risk of reinfection of SARS-CoV-2, strengthen public health education, maintain healthy habits, and reduce the risk of reinfection.
Topics: Humans; SARS-CoV-2; COVID-19; Reinfection; Health Education; Hospitalization
PubMed: 36834029
DOI: 10.3390/ijerph20043335 -
Endocrine Nov 2023The prevalence of type 2 diabetes mellitus (T2DM) is increasing each year and has become one of the most prominent health concerns worldwide. Patients with T2DM are... (Meta-Analysis)
Meta-Analysis
BACKGROUND
The prevalence of type 2 diabetes mellitus (T2DM) is increasing each year and has become one of the most prominent health concerns worldwide. Patients with T2DM are prone to infectious diseases, and urinary tract infections are also widespread. Despite a comprehensive understanding of urinary tract infection (UTI), there is a lack of research regarding primary prevention strategies for asymptomatic bacteriuria (ASB).
OBJECTIVE
To clarify the incidence and risk factors of asymptomatic urinary tract infection in patients with T2DM by meta-analysis to provide evidence for preventing UTI. Help patients, their families, and caregivers to identify the risk factors of patients in time and intervene to reduce the incidence of ASB in patients with T2DM. Fill in the gaps in existing research.
STUDY DESIGN
Meta-analyses were conducted in line with PRISMA guidelines.
METHODS
Eleven databases were systematically searched for articles about ASB in T2DM, and the retrieval time was selected from the establishment of the database to February 5, 2023. Literature screening, quality evaluation, and meta-analysis were independently performed by two researchers according to the inclusion and exclusion criteria, and a meta-analysis was performed using Stata 17.0.
RESULTS
Fourteen articles were included, including cohort and case-control studies. A meta-analysis of 4044 patients with T2DM was included. The incidence of ASB in patients with T2DM was 23.7%(95% CI (0.183, 0.291); P < 0.001). After controlling for confounding variables, the following risk factors were associated with ASB in patients with T2DM: age (WMD = 3.18, 95% CI (1.91, 4.45), I = 75.5%, P < 0.001), female sex (OR = 1.07, 95% CI(1.02, 1.12), I = 79.3%, P = 0.002), duration of type 2 diabetes (WMD = 2.54, 95% CI (1.53, 5.43), I = 80.7%, P < 0.001), HbA1c (WMD = 0.63, 95% CI (0.43, 0.84), I = 62.6,%. P < 0.001), hypertension (OR = 1.59, 95% CI (1.24, 2.04), I = 0%, <0.001), hyperlipidemia (OR = 1.66, 95% CI (1.27, 2.18), I = 0%, P < 0.001), Neuropathy (OR = 1.81, 95% CI (1.38, 2.37), I = 0%, P < 0.001), proteinuria (OR = 3.00, 95% CI (1.82, 4.95), I = 62.7%, P < 0.001).
CONCLUSION
The overall prevalence of ASB in T2DM is 23.7%. Age, female sex, course of T2DM, HbA1C, hypertension, hyperlipidemia, neuropathy, and proteinuria were identified as related risk factors for ASB in T2DM. These findings can provide a robust theoretical basis for preventing and managing ASB in T2DM.
Topics: Humans; Female; Bacteriuria; Diabetes Mellitus, Type 2; Incidence; Glycated Hemoglobin; Risk Factors; Urinary Tract Infections; Proteinuria; Hyperlipidemias; Hypertension
PubMed: 37599328
DOI: 10.1007/s12020-023-03469-6 -
The Lancet. Microbe Apr 2023The efficacy of SARS-CoV-2 vaccines in preventing severe COVID-19 illness and death is uncertain due to the rarity of data in individual trials. How well the antibody... (Meta-Analysis)
Meta-Analysis
BACKGROUND
The efficacy of SARS-CoV-2 vaccines in preventing severe COVID-19 illness and death is uncertain due to the rarity of data in individual trials. How well the antibody concentrations can predict the efficacy is also uncertain. We aimed to assess the efficacy of these vaccines in preventing SARS-CoV-2 infections of different severities and the dose-response relationship between the antibody concentrations and efficacy.
METHODS
We did a systematic review and meta-analysis of randomised controlled trials (RCTs). We searched PubMed, Embase, Scopus, Web of Science, Cochrane Library, WHO, bioRxiv, and medRxiv for papers published between Jan 1, 2020 and Sep 12, 2022. RCTs on the efficacy of SARS-CoV-2 vaccines were eligible. Risk of bias was assessed using the Cochrane tool. A frequentist, random-effects model was used to combine efficacy for common outcomes (ie, symptomatic and asymptomatic infections) and a Bayesian random-effects model was used for rare outcomes (ie, hospital admission, severe infection, and death). Potential sources of heterogeneity were investigated. The dose-response relationships of neutralising, spike-specific IgG and receptor binding domain-specific IgG antibody titres with efficacy in preventing SARS-CoV-2 symptomatic and severe infections were examined by meta-regression. This systematic review is registered with PROSPERO, CRD42021287238.
FINDINGS
28 RCTs (n=286 915 in vaccination groups and n=233 236 in placebo groups; median follow-up 1-6 months after last vaccination) across 32 publications were included in this review. The combined efficacy of full vaccination was 44·5% (95% CI 27·8-57·4) for preventing asymptomatic infections, 76·5% (69·8-81·7) for preventing symptomatic infections, 95·4% (95% credible interval 88·0-98·7) for preventing hospitalisation, 90·8% (85·5-95·1) for preventing severe infection, and 85·8% (68·7-94·6) for preventing death. There was heterogeneity in the efficacy of SARS-CoV-2 vaccines against asymptomatic and symptomatic infections but insufficient evidence to suggest whether the efficacy could differ according to the type of vaccine, age of the vaccinated individual, and between-dose interval (p>0·05 for all). Vaccine efficacy against symptomatic infection waned over time after full vaccination, with an average decrease of 13·6% (95% CI 5·5-22·3; p=0·0007) per month but can be enhanced by a booster. We found a significant non-linear relationship between each type of antibody and efficacy against symptomatic and severe infections (p<0·0001 for all), but there remained considerable heterogeneity in the efficacy, which cannot be explained by antibody concentrations. The risk of bias was low in most studies.
INTERPRETATION
The efficacy of SARS-CoV-2 vaccines is higher for preventing severe infection and death than for preventing milder infection. Vaccine efficacy wanes over time but can be enhanced by a booster. Higher antibody titres are associated with higher estimates of efficacy but precise predictions are difficult due to large unexplained heterogeneity. These findings provide an important knowledge base for interpretation and application of future studies on these issues.
FUNDING
Shenzhen Science and Technology Programs.
Topics: Humans; COVID-19 Vaccines; Asymptomatic Infections; COVID-19; SARS-CoV-2; Immunoglobulin G; Randomized Controlled Trials as Topic
PubMed: 36868258
DOI: 10.1016/S2666-5247(22)00390-1 -
Vaccines Jun 2021Human papillomavirus (HPV) infection is the most common sexually transmitted infection worldwide. Although most HPV infections are transient and asymptomatic, persistent... (Review)
Review
Human papillomavirus (HPV) infection is the most common sexually transmitted infection worldwide. Although most HPV infections are transient and asymptomatic, persistent infection with high-risk HPV types may results in diseases. Although there are currently three effective and safe prophylactic HPV vaccines that are used across the world, HPV vaccination coverage remains low. This review evaluates the effects of the interventions to improve HPV vaccination coverage. We searched the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, Scopus, and the World Health Organization International Clinical Trials Registry Platform and checked the reference lists of relevant articles for eligible studies. Thirty-five studies met inclusion criteria. Our review found that various evaluated interventions have improved HPV vaccination coverage, including narrative education, outreach plus reminders, reminders, financial incentives plus reminders, brief motivational behavioral interventions, provider prompts, training, training plus assessment and feedback, consultation, funding, and multicomponent interventions. However, the evaluation of these intervention was conducted in high-income countries, mainly the United States of America. There is, therefore, a need for studies to evaluate the effect of these interventions in low-and middle-income countries, where there is a high burden of HPV and limited HPV vaccination programs.
PubMed: 34201421
DOI: 10.3390/vaccines9070687 -
The Cochrane Database of Systematic... Aug 2021Systemic corticosteroids are used to treat people with COVID-19 because they counter hyper-inflammation. Existing evidence syntheses suggest a slight benefit on... (Review)
Review
BACKGROUND
Systemic corticosteroids are used to treat people with COVID-19 because they counter hyper-inflammation. Existing evidence syntheses suggest a slight benefit on mortality. So far, systemic corticosteroids are one of the few treatment options for COVID-19. Nonetheless, size of effect, certainty of the evidence, optimal therapy regimen, and selection of patients who are likely to benefit most are factors that remain to be evaluated.
OBJECTIVES
To assess whether systemic corticosteroids are effective and safe in the treatment of people with COVID-19, and to keep up to date with the evolving evidence base using a living systematic review approach.
SEARCH METHODS
We searched the Cochrane COVID-19 Study Register (which includes PubMed, Embase, CENTRAL, ClinicalTrials.gov, WHO ICTRP, and medRxiv), Web of Science (Science Citation Index, Emerging Citation Index), and the WHO COVID-19 Global literature on coronavirus disease to identify completed and ongoing studies to 16 April 2021.
SELECTION CRITERIA
We included randomised controlled trials (RCTs) that evaluated systemic corticosteroids for people with COVID-19, irrespective of disease severity, participant age, gender or ethnicity. We included any type or dose of systemic corticosteroids. We included the following comparisons: systemic corticosteroids plus standard care versus standard care (plus/minus placebo), dose comparisons, timing comparisons (early versus late), different types of corticosteroids and systemic corticosteroids versus other active substances. We excluded studies that included populations with other coronavirus diseases (severe acute respiratory syndrome or Middle East respiratory syndrome), corticosteroids in combination with other active substances versus standard care, topical or inhaled corticosteroids, and corticosteroids for long-COVID treatment.
DATA COLLECTION AND ANALYSIS
We followed standard Cochrane methodology. To assess the risk of bias in included studies, we used the Cochrane 'Risk of bias' 2 tool for RCTs. We rated the certainty of evidence using the GRADE approach for the following outcomes: all-cause mortality, ventilator-free days, new need for invasive mechanical ventilation, quality of life, serious adverse events, adverse events, and hospital-acquired infections.
MAIN RESULTS
We included 11 RCTs in 8075 participants, of whom 7041 (87%) originated from high-income countries. A total of 3072 participants were randomised to corticosteroid arms and the majority received dexamethasone (n = 2322). We also identified 42 ongoing studies and 16 studies reported as being completed or terminated in a study registry, but without results yet. Hospitalised individuals with a confirmed or suspected diagnosis of symptomatic COVID-19 Systemic corticosteroids plus standard care versus standard care plus/minus placebo We included 10 RCTs (7989 participants), one of which did not report any of our pre-specified outcomes and thus our analysis included outcome data from nine studies. All-cause mortality (at longest follow-up available): systemic corticosteroids plus standard care probably reduce all-cause mortality slightly in people with COVID-19 compared to standard care alone (median 28 days: risk difference of 30 in 1000 participants fewer than the control group rate of 275 in 1000 participants; risk ratio (RR) 0.89, 95% confidence interval (CI) 0.80 to 1.00; 9 RCTs, 7930 participants; moderate-certainty evidence). Ventilator-free days: corticosteroids may increase ventilator-free days (MD 2.6 days more than control group rate of 4 days, 95% CI 0.67 to 4.53; 1 RCT, 299 participants; low-certainty evidence). Ventilator-free days have inherent limitations as a composite endpoint and should be interpreted with caution. New need for invasive ventilation: the evidence is of very low certainty. Because of high risk of bias arising from deaths that occurred before ventilation we are uncertain about the size and direction of the effects. Consequently, we did not perform analysis beyond the presentation of descriptive statistics. Quality of life/neurological outcome: no data were available. Serious adverse events: we included data on two RCTs (678 participants) that evaluated systemic corticosteroids compared to standard care (plus/minus placebo); for adverse events and hospital-acquired infections, we included data on five RCTs (660 participants). Because of high risk of bias, heterogeneous definitions, and underreporting we are uncertain about the size and direction of the effects. Consequently, we did not perform analysis beyond the presentation of descriptive statistics (very low-certainty evidence). Different types, dosages or timing of systemic corticosteroids We identified one study that compared methylprednisolone with dexamethasone. The evidence for mortality and new need for invasive mechanical ventilation is very low certainty due to the small number of participants (n = 86). No data were available for the other outcomes. We did not identify comparisons of different dosages or timing. Outpatients with asymptomatic or mild disease Currently, there are no studies published in populations with asymptomatic infection or mild disease.
AUTHORS' CONCLUSIONS
Moderate-certainty evidence shows that systemic corticosteroids probably slightly reduce all-cause mortality in people hospitalised because of symptomatic COVID-19. Low-certainty evidence suggests that there may also be a reduction in ventilator-free days. Since we are unable to adjust for the impact of early death on subsequent endpoints, the findings for ventilation outcomes and harms have limited applicability to inform treatment decisions. Currently, there is no evidence for asymptomatic or mild disease (non-hospitalised participants). There is an urgent need for good-quality evidence for specific subgroups of disease severity, for which we propose level of respiratory support at randomisation. This applies to the comparison or subgroups of different types and doses of corticosteroids, too. Outcomes apart from mortality should be measured and analysed appropriately taking into account confounding through death if applicable. We identified 42 ongoing and 16 completed but not published RCTs in trials registries suggesting possible changes of effect estimates and certainty of the evidence in the future. Most ongoing studies target people who need respiratory support at baseline. With the living approach of this review, we will continue to update our search and include eligible trials and published data.
Topics: Adrenal Cortex Hormones; COVID-19; Humans; Immunization, Passive; Randomized Controlled Trials as Topic; Respiration, Artificial; SARS-CoV-2; COVID-19 Drug Treatment
PubMed: 34396514
DOI: 10.1002/14651858.CD014963 -
PLoS Neglected Tropical Diseases Jun 2018Chikungunya virus (CHIKV) is an emerging arboviral infection with a global distribution and may cause fetal and neonatal infections after maternal CHIKV-infections... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Chikungunya virus (CHIKV) is an emerging arboviral infection with a global distribution and may cause fetal and neonatal infections after maternal CHIKV-infections during gestation.
METHODOLOGY
We performed a systematic review to evaluate the risk for: a) mother-to-child transmission (MTCT), b) antepartum fetal deaths (APFD), c) symptomatic neonatal disease, and d) neonatal deaths from maternal CHIKV-infections during gestation. We also recorded the neonatal clinical manifestations after such maternal infections (qualitative data synthesis). We searched PubMed (last search 3/2017) for articles, of any study design, with any of the above outcomes. We calculated the overall risk of MTCT, APFDs and risk of symptomatic neonatal disease by simple pooling. For endpoints with ≥5 events in more than one study, we also synthesized the data by random-effect-model (REM) meta-analysis.
PRINCIPAL FINDINGS
Among 563 identified articles, 13 articles from 8 cohorts were included in the quantitative data synthesis and 33 articles in the qualitative data synthesis. Most cohorts reported data only on symptomatic rather than on all neonatal infections. By extrapolation also of these data, the overall pooled-MTCT-risk across cohorts was at least 15.5% (206/1331), (12.6% by REMs). The pooled APFD-risk was 1.7% (20/1203); while the risk of CHIKV-confirmed-APFDs was 0.3% (3/1203). Overall, the pooled-risk of symptomatic neonatal disease was 15.3% (203/1331), (11.9% by REMs). The pooled risk of symptomatic disease was 50.0% (23/46) among intrapartum vs 0% (0/712) among antepartum/peripartum maternal infections. Infected newborns, from maternal infections during gestation were either asymptomatic or presented within their first week of life, but not at birth, with fever, irritability, hyperalgesia, diffuse limb edema, rashes and occasionally sepsis-like illness and meningoencephalitis. The pooled-risk of neonatal death was 0.6% (5/832) among maternal infections and 2.8% (5/182) among neonatal infections; long-term neurodevelopmental delays occurred in 50% of symptomatic neonatal infections.
CONCLUSIONS/SIGNIFICANCE
Published cohorts with data on the risk to the fetus and/or newborn from maternal CHIKV-infections during gestation were sparse compared to the number of recently reported CHIKV-infection outbreaks worldwide; however perinatal infections do occur, at high rates during intrapartum period, and can be related to neonatal death and long-term disabilities.
Topics: Chikungunya Fever; Chikungunya virus; Female; Humans; Infant, Newborn; Infant, Newborn, Diseases; Infectious Disease Transmission, Vertical; Male; Pregnancy; Pregnancy Complications, Infectious
PubMed: 29897898
DOI: 10.1371/journal.pntd.0006510 -
Journal of Parasitology Research 2021Malaria is one of the most public health important and life-threatening parasitic infections caused by the protozoan parasite. Since children are immunologically naive... (Review)
Review
BACKGROUND
Malaria is one of the most public health important and life-threatening parasitic infections caused by the protozoan parasite. Since children are immunologically naive to the malaria parasite, they are the main vulnerable groups. During malaria infection, they might have a complication of anemia, cerebral malaria, coma, respiratory distress, and a decrease in cognitive and behavioral improvement. Therefore, this review was aimed at determining the pooled prevalence of malaria among children in Ethiopia.
METHODS
The current systematic review and meta-analysis were conducted based on the guideline of Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guideline. Electronic bibliographic databases such as Google Scholar, PubMed, and Science Direct were used for searching relevant literature. Besides, the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI) was used for critical appraisal of studies. Using the STATA 14 software, the pooled Meta logistic regression was computed to present the pooled prevalence with a 95% confidence interval (CI).
RESULT
The overall estimated pooled prevalence of malaria among children in Ethiopia was 9.07 (95% CI: 6.32, 11.82). Subgroup analysis based on malaria signs and symptoms showed that the pooled prevalence of malaria among asymptomatic and symptomatic children was 6.67% (95% CI: 0.36, 12.98) and 27.17% (95% CI: 18.59, 35.76), respectively.
CONCLUSION
The findings revealed a high prevalence of malaria among children in Ethiopia. As a result, still there is a need of improving and rechecking the existing malaria prevention and control measures of the country.
PubMed: 33936806
DOI: 10.1155/2021/6697294 -
Annals of the Royal College of Surgeons... Apr 2020Since the seminal works by Singh and Blandy in the 1970s, the management of staghorn stones has almost exclusively involved surgical intervention. In contrast, a more...
INTRODUCTION
Since the seminal works by Singh and Blandy in the 1970s, the management of staghorn stones has almost exclusively involved surgical intervention. In contrast, a more recent study found that conservative management was not as unsafe as previously believed. The present review sought to examine the available literature to understand the implications of a conservative strategy.
METHODS
A systematic search of the literature was carried out using MEDLINE, Embase™ and the Cochrane Central Register of Controlled Trials. All papers looking at management of staghorn calculi were reviewed and studies with a conservative management arm were identified. Outcomes of interest were recurrent or severe urinary tract infections, progressive renal deterioration, dialysis requirements, morbidity and disease specific mortality. Owing to the lack of relevant data, a descriptive review was carried out.
RESULTS
Our literature search yielded 10 suitable studies involving a total of 304 patients with staghorn stones managed conservatively. Progressive renal deterioration occurred in 0-100% of cases (mean 27.5%) with a higher rate among bilateral staghorn sufferers (44% vs 9%). Dialysis was required in 9% of patients (20% bilateral, 6% unilateral). The mean rate of severe infection was 8.7% and recurrent urinary tract infections occurred in as high as 50% of cases (80% bilateral, 41% unilateral). Disease specific mortality ranged from 0% to 67% (mean 20.5%).
CONCLUSIONS
It appears that conservative management of staghorn calculi is not as unsafe as previously thought and selection of patients with unilateral asymptomatic stones with minimal infection should be considered.
Topics: Conservative Treatment; Humans; Renal Dialysis; Renal Insufficiency; Severity of Illness Index; Staghorn Calculi; Urinary Tract Infections
PubMed: 31918554
DOI: 10.1308/rcsann.2019.0176 -
Epidemiology (Cambridge, Mass.) Nov 2015The fraction of persons with influenza virus infection, who do not report any signs or symptoms throughout the course of infection is referred to as the asymptomatic... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
The fraction of persons with influenza virus infection, who do not report any signs or symptoms throughout the course of infection is referred to as the asymptomatic fraction.
METHODS
We conducted a systematic review and meta-analysis of published estimates of the asymptomatic fraction of influenza virus infections. We found that estimates of the asymptomatic fraction were reported from two different types of studies: first, outbreak investigations with short-term follow-up of potentially exposed persons and virologic confirmation of infections; second, studies conducted across epidemics typically evaluating rates of acute respiratory illness among persons with serologic evidence of infection, in some cases adjusting for background rates of illness from other causes.
RESULTS
Most point estimates from studies of outbreak investigations fell in the range 4%-28% with low heterogeneity (I = 0%) with a pooled mean of 16% (95% confidence interval = 13%, 19%). Estimates from the studies conducted across epidemics without adjustment were very heterogeneous (point estimates 0%-100%; I = 97%), while estimates from studies that adjusted for background illnesses were more consistent with point estimates in the range 65%-85% and moderate heterogeneity (I = 58%). Variation in estimates could be partially explained by differences in study design and analysis, and inclusion of mild symptomatic illnesses as asymptomatic in some studies.
CONCLUSIONS
Estimates of the asymptomatic fraction are affected by the study design, and the definitions of infection and symptomatic illness. Considerable differences between the asymptomatic fraction of infections confirmed by virologic versus serologic testing may indicate fundamental differences in the interpretation of these two indicators.
Topics: Asymptomatic Infections; Disease Outbreaks; Epidemics; Humans; Influenza, Human
PubMed: 26133025
DOI: 10.1097/EDE.0000000000000340