Seroepidemiological Study Research Articles

Cohort profile: a longitudinal regional cohort study to assess COVID-19 seroprevalence in blood donors – baseline characteristics of the SeMaCo study participants

PurposeThe SeMaCo study (Serologische Untersuchungen bei Blutspendern des Großraums Magdeburg auf Antikörper gegen SARS-CoV-2), a prospective, longitudinal cohort study with four survey phases spanning 3–5 months each over a period...

Seroprevalence of COVID-19 infection in a rural district of Tamil Nadu: A population-based seroepidemiological study

Background: Coronavirus disease 2019 (COVID-19) was a recent global pandemic of the era which posed a great challenge for the health care in terms of preventive, diagnostic and treatment dimensions. The seroprevalence rate of COVID IgG antibodies is very crucial in estimating the susceptibility of a particular area to the viral disease. In our study, we estimated the seroprevalence of COVID-19 in a rural area. Aims and Objectives: We aimed to estimate the seroprevalence of COVID-19 in a rural district of Tamil Nadu, 6 months after the index case. Materials and Methods: We conducted a cross-sectional study of 509 adults aged more than 18 years. From all the seven Taluks, two gram panchayats (administrative cluster of 8–10 villages) were randomly selected followed by one village through convenience. The participants were invited for the study to the community-based study kiosk set up in all the eight villages through village health committees. We collected sociodemographic characteristics and symptoms using a mobile application-based questionnaire, and we tested samples for the presence of IgG antibodies for severe acute respiratory syndrome coronavirus 2 using an electro chemiluminescent immunoassay. We calculated age-gender adjusted and test performance adjusted seroprevalence. Results: The age-and gender-adjusted seroprevalence was 8.5% (95% confidence interval [CI] 6.9–10.8%). The unadjusted seroprevalence among participants with hypertension and diabetes was 16.3% (95% CI: 9.2–25.8) and 10.7% (95% CI: 5.5–18.3), respectively. When we adjusted for the test performance, the seroprevalence was 6.1% (95% CI 4.02–8.17). The study estimated 7 (95% CI 1:4.5–1:9) undetected infected individuals for every reverse transcription polymerase chain reaction confirmed case. Infection fatality rate (IFR) was calculated as 12.38/10,000 infections as on October 22, 2020. History of self-reported symptoms and education were significantly associated with positive status (P<0.05). Conclusion: A significant proportion of the rural population in a district of Tamil Nadu remains susceptible to COVID-19. A higher proportion of susceptible, relatively higher IFR, and a poor tertiary health-care network stress the importance of sustaining the public health measures and promoting early access to the vaccine are crucial to preserving the health of this population. Low population density, good housing, adequate ventilation, limited urbanization combined with public, private, and local health leadership are critical components of curbing future respiratory pandemics.

Development and validation of a flow cytometry antibody test for Lawsonia intracellularis.

Lawsonia intracellularis is the etiologic agent of porcine proliferative enteropathy (PPE), an inflammatory bowel disease with a major economic impact on the pig industry. The serological diagnosis of PPE can be performed using Blocking or Indirect ELISA, Immunoperoxidase Monolayer Assay (IPMA) and Indirect Fluorescence Antibody Test (IFAT). Here, we designed a most sophisticated immunological method for the detection of porcine anti-L. intracellularis IgGs, named Flow Cytometry Antibody Test - FCAT. This assay uses whole, live-attenuated L. intracellularis bacteria derived from a commercial vaccine. For the assay, we set up the optimal antigen concentration (106 bacterium/assay), primary antibody dilution (1:100), time of incubation (20min), antigen stability (15 days), precision (coefficient of variation - CV < 10%), reproducibility (CV ≤ 13%) and Receiver Operating Characteristic (ROC). When using a cut-off of >15.15% for FCAT, we determined that it showed a sensitivity of 98.8% and specificity of 100%. The rate of agreement with IPMA was 84.09% with a kappa index of 0.66. FCAT was used to screen 1,000 sera from non-vaccinated pigs housed in 22 different farms and we found that 730 pigs (73%) from 16 farms (72.7%) had L. intracellularis IgG. This high prevalence confirms that L. intracellularis is endemic on Brazilian pig farms. Finally, we determined that FCAT is an easy to perform diagnostic assay and we would highly recommend it for: i) seroepidemiological studies; ii) evaluation of infection dynamics; and iii) characterization of the humoral response profile induced by vaccines.

Zika, Flavivirus and Malaria Antibody Cocirculation in Nigeria

Introduction. Arboviruses and malaria pose a growing threat to public health, affecting not only the general population but also immunocompromised individuals and pregnant women. Individuals in vulnerable groups are at a higher risk of severe complications from the co-circulation and transmission of ZIKV, malaria, and FLAVI fever. In sub-Saharan countries, such as Nigeria, these mosquito-borne infections have clinical presentations that overlap with other diseases (dengue, West Nile virus, and Japanese encephalitis, chikungunya, and O'nyong o'nyong virus), making them a diagnostic challenge for clinicians in regions where they co-circulate. Vertical transmission can have a devastating impact on maternal health and fetal outcomes, including an increased risk of fetal loss and premature birth. Despite the global recognition of the burden of malaria and arboviruses, particularly ZIKV and other flaviviruses, there is limited data on their prevalence in Nigeria. In urban settings, where these diseases are endemic and share common biological, ecological, and economic factors, they may impact treatment outcomes and lead to epidemiological synergy. Hence, it is imperative to conduct sero-epidemiological and clinical studies to better understand the disease burden and hidden endemicity, thereby enabling improved prevention and clinical management. Method. Serum samples collected from outpatients between December 2020 and November 2021 in three regions of Nigeria were tested for the presence of IgG antibody seropositivity against ZIKV and FLAVI using immunoblot serological assay. Results. The overall cohort co-circulation antibody seropositivity of ZIKV, FLAVI and malaria was 24.0% (209/871). A total of 19.2% (167/871) of the study participants had ZIKV-seropositive antibodies and 6.2% (54/871) were FLAVI-seropositive, while 40.0% (348/871) of the subjects had malaria parasite antigens. Regional analysis revealed that participants from the southern region had the highest antibody seropositivity against ZIKV (21.7% (33/152)) and FLAVI (8.6% (13/152)), whereas those from the central region had a higher malaria parasite antigen (68.5% (287/419)). Conclusions. This study represents the largest comparative cross-sectional descriptive sero-epidemiological investigation of ZIKV-FLAVI and malaria cocirculation in Nigeria. The findings of this study revealed increased antibody seropositivity, hidden endemicity, and the burden of ZIKV, FLAVI, and malaria co-circulating in Nigeria.

Plasmodium vivax MSP1-42 kD Variant Proteins Detected Naturally Induced IgG Antibodies in Patients Regardless of the Infecting Parasite Phenotype in Mesoamerica

The serological tests using blood stage antigens might be helpful for detecting recent exposure to Plasmodium parasites, and seroepidemiological studies would aid in the elimination of malaria. This work produced recombinant proteins of PvMSP142 variants and evaluated their capacity to detect IgG antibodies in symptomatic patients from Mesoamerica. Three variant Pvmsp142 genes were cloned in the pHL-sec plasmid, expressed in the Expi293F™ eukaryotic system, and the recombinant proteins were purified by affinity chromatography. Using an ELISA, 174 plasma or eluted samples from patients infected with different P. vivax haplotypes were evaluated against PvMSP142 proteins and to a native blood stage antigen (NBSA). The antibody IgG OD values toward PvMSP142 variants (v88, v21, and v274) were heterogeneous (n = 178; median = 0.84 IQR 0.28-1.64). The correlation of IgG levels among all proteins was very high (spearman's rho = 0.96-0.98; p < 0.0001), but was lower between them and the NBSA (rho = 0.771; p < 0.0001). In only a few samples, higher reactivity to the homologous protein was evident. Patients with a past infection who were seropositive had higher IgG levels and lower parasitemia levels than those who did not (p < 0.0001). The PvMSP142 variants were similarly efficient in detecting specific IgG antibodies in P. vivax patients from Mesoamerica, regardless of the infecting parasite's haplotype, and might be good candidates for malaria surveillance and epidemiological studies in the region.

A Sero-Epidemiological Study on Visceral Leishmaniasis among Volunteer Children and Adults in Rural Areas of Shahroud, Iran 2018-2019.

Visceral leishmaniasis (VL) also known as Kala-azar is considered as one of the zoonotic infections in Mediterranean countries. The disease reservoir and vectors are dogs and sandflies respectively. Due to reported sporadic cases of Kala-azar in the past five years in Shahroud County, Semnan Province, Iran, this study aimed to investigate the status of this infection in this area and to determine its seroepidemiology to take required measurements for infection control and treatment. This study was conducted on 504 subjects residing in seven villages in Shahroud County. Blood samples were randomly selected using the cluster sampling method and were collected from subjects aged up to 13 years old (90%) and adults over 13 years old (10%) from September to May 2019. After separating sera from whole blood, samples were subjected to direct agglutination test (DAT) to detect anti-Leishmania infantum antibodies. A range of 1:10 to 1:800 dilutions were prepared from the samples. Results of 1:800 titration indicated that no sample was positive for antibodies against L. infantum. After the secondary screening, 10 cases (1.98%) showed the antibody titer of 1:100, while four cases (0.79%) showed the antibody titer of 1:400. Of 14 cases with the L. infantum antibodies, all were detected from the children <13 years old. According to clinical findings, no patient was suffering from fever, weight loss, splenomegaly, hepatomegaly, and cachexia and therefore did not show the Kala-azar symptoms. The results of the current study indicate that Kala-azar is not prevalent in Shahroud County.

Seroprevalence of Coxiella burnetii in sheep and goats in the Istrian Region, Croatia

A seroepidemiological study was conducted on the presence of Coxiella burnetii (C. burnetii) antibodies in sheep and goats in Istria, the largest peninsula in Croatia. Random blood samples were taken from 634 sheep and goats at different localities throughout the region. The aim of the study was to assess the prevalence of C. burnetii infection in sheep and goats, which represent the most important reservoir of infection in humans. C. burnetii antibody detection was performed by ELISA (LSIVet Ruminant Q Fever-Serum/Milk). Seroprevalence of C. burnetii was proven in 6.2% of sheep and 3.5% of goats. Larger herds, poor hygienic conditions on farms, a higher presence of goats in a restricted area, and the northern part of Istria proved to be significant risk factors for the seropositivity of animals.The southern part of Istria is known to have endemic Q fever, but no studies have been carried out so far to explore this issue. To gain a more complete epidemiological picture of Q fever in Istria, studies in humans, especially those professionally exposed to C. burnetii infection, should be performed.

National seroepidemiological study of COVID-19 after the initial rollout of vaccines: Before and at the peak of the Omicron-dominant period in Japan.

Based on routine surveillance data, Japan has been affected much less by COVID-19 compared with other countries. To validate this, we aimed to estimate SARS-CoV-2 seroprevalence and examine sociodemographic factors associated with cumulative infection in Japan. A population-based serial cross-sectional seroepidemiological investigation was conducted in five prefectures in December 2021 (pre-Omicron) and February-March 2022 (Omicron [BA.1/BA.2]-peak). Anti-nucleocapsid and anti-spike antibodies were measured to detect infection-induced and vaccine/infection-induced antibodies, respectively. Logistic regression was used to identify associations between various factors and past infection. Among 16 296 participants (median age: 53 [43-64] years), overall prevalence of infection-induced antibodies was 2.2% (95% CI: 1.9-2.5%) in December 2021 and 3.5% (95% CI: 3.1-3.9%) in February-March 2022. Factors associated with past infection included those residing in urban prefectures (Tokyo: aOR 3.37 [95% CI: 2.31-4.91], Osaka: aOR 3.23 [95% CI: 2.17-4.80]), older age groups (60s: aOR 0.47 [95% CI 0.29-0.74], 70s: aOR 0.41 [95% CI 0.24-0.70]), being vaccinated (twice: aOR 0.41 [95% CI: 0.28-0.61], three times: aOR 0.21 [95% CI: 0.12-0.36]), individuals engaged in occupations such as long-term care workers (aOR: 3.13 [95% CI: 1.47-6.66]), childcare workers (aOR: 3.63 [95% CI: 1.60-8.24]), food service workers (aOR: 3.09 [95% CI: 1.50-6.35]), and history of household contact (aOR: 26.4 [95% CI: 20.0-34.8]) or non-household contact (aOR: 5.21 [95% CI:3.80-7.14]) in February-March 2022. Almost all vaccinated individuals (15 670/15 681) acquired binding antibodies with higher titers among booster dose recipients. Before Omicron, the cumulative burden was >10 times lower in Japan (2.2%) compared with the US (33%), the UK (25%), or global estimates (45%), but most developed antibodies owing to vaccination.

Sero-Epidemiological Study of Varicella in the Italian General Population.

The aim of this study was to analyze the seroprevalence of varicella in Italy and to evaluate the impact of varicella vaccination, which has been mandatory for newborns since 2017. The levels of VZV-specific IgG antibodies were determined by the ELISA method in residual serum samples obtained from subjects aged between 6 and 64 years and residing in 13 Italian regions. Overall, 3746 serum samples were collected in the years 2019 and 2020. The overall seroprevalence was 91.6% (89.9% in males and 93.3% in females; p = 0.0002). Seroprevalence showed an increasing trend (p < 0.0001) starting in the younger age groups: 6-9 years: 84.1%; 10-14 years: 88.7%; 15-19 years: 89.3%; 20-39 years: 93.1% and >40 years: 97.0%. The seroprevalence data obtained in the present study were compared with those relating to previous sero-epidemiological surveys conducted, respectively, in the years 1996-1997, 2003-2004 and 2013-2014, taking into consideration only data from regions monitored in all surveillance campaigns. The comparison highlighted for the period 2019-2020 showed significantly higher values in the age groups 6-9 (p < 0.001), 10-14 (p = 0.018) and 15-19 years (p = 0.035), while in adults, the trend did not change over time (ns). These results highlight the positive impact of varicella vaccination in Italy.

Seroepidemiological study of Toxoplasma gondii in equids in different European countries.

Toxoplasmosis, caused by the obligate intracellular protozoan Toxoplasma gondii, is a worldwide parasitic zoonosis. A cross-sectional study was carried out to determine the exposure to T. gondii in equids in Europe. Serum samples from 1399 equids (1085 horses, 238 donkeys, and 76 mules/hinnies) bred in four European countries (Italy, Spain, United Kingdom [UK], and Ireland) were collected during the period of 2013-2021. The overall seroprevalence of T. gondii was 18.9% (95% Confidence Interval [CI]: 16.9-21.0) by using the modified agglutination test (MAT) at a cut-off of 1:25. Seropositivity by country was 27.1% in Italy, 16.6% in Spain, 12.0% in UK and 7.0% in Ireland. Anti-T. gondii antibodies were detected in 12.8% of the horses, 43.7% of the donkeys, and in 28.9% of the mules/hinnies. A Generalized Estimating Equation (GEE) analysis was carried out to study the associations between seropositivity and explanatory variables related to individuals, herds, and management measures on these herds, selected based on the bivariate analysis. The risk for being seropositive for T. gondii was 5.3 and 2.7 times higher in donkeys and mules/hinnies than in horses, respectively. In addition, significantly higher seropositivity was observed in horses from herds that used disinfectants less than once a week (13.9%; p=0.038, odds ratio [OR]=1.6; 95% CI: 1.03-2.62) compared with those from herds that performed weekly disinfection of the facilities (9.4%). This is the first large-scale seroepidemiological study on T. gondii comprising horses, donkeys, and mules/hinnies in Europe and the first report of T. gondii exposure in horses from Ireland and UK. We found a widespread distribution of T. gondii among equid populations in different European countries. The seroprevalence found in these species, especially in donkeys and mules/hinnies, highlights the potential risk of human infection through the consumption of their raw/undercooked milk or meat.

Understanding the epidemiology of iNTS disease in Africa in preparation for future iNTS- vaccine studies in endemic countries: Seroepidemiology in Africa of iNTS (SAiNTS) Study Protocol [Version 9.0

Background: Non-typhoidal Salmonella (NTS) are a major cause of bloodstream infections amongst children in sub-Saharan Africa. A clear understanding of the seroepidemiology and correlates of protection for invasive NTS (iNTS) in relation to key risk factors (malaria, anaemia, malnutrition) in children in Africa is needed to inform strategies for disease control including vaccine implementation. Methodology: The SAiNTS study is a prospective community cohort study with paired serology samples from 2500 children 0-5 years at baseline and three months to measure age-stratified acquisition of lipopolysaccharide (LPS) O-antigen antibody (IgG) and serum bactericidal activity to the main serovars causing iNTS (Salmonella typhimurium and S. enteritidis). Children are selected from mapped and censused randomly selected households in Chikwawa, Malawi; an area with substantial malaria burden. The sampling framework is set within a malaria vaccination (RTS,S/ AS01) phase 4 cluster randomized trial (EPIMAL), allowing exploration of the impact of malaria vaccination on acquisition of immunity to NTS. Data on risk factors for invasive disease: malaria, anaemia and malnutrition as well as indicators of socioeconomic status and water and sanitation, will be collected using rapid diagnostic tests, anthropometry and electronic CRF’s. Stool sample analysis includes NTS culture and pan-Salmonella polymerase chain reaction to assess enteric exposure and biomarkers of environmental enteric dysfunction. Cases with iNTS disease will be followed up for comparison with community controls. Conclusions: The final cohort of 2500 children will allow investigation into the impact of risk factors for iNTS on the acquisition of immunity in children 0-5 years in an endemic setting, including comparisons to partner sero-epidemiology studies in three other sub-Saharan African sites. The data generated will be key to informing iNTS disease control measures including targeted risk factor interventions and vaccine implementation through investigation of correlates of protection and identifying windows of immune susceptibility in at-risk populations.

Nigeria healthcare worker SARS-CoV-2 serology study: Results from a prospective, longitudinal cohort.

Healthcare workers, both globally and in Nigeria, have an increased risk for SARS-CoV-2 infection compared with the general population due to higher risk contacts, including occupational exposures. In addition, primary healthcare workers represent an important group for estimating prior infection to SARS-CoV-2 because they work at the first point-of-contact for most patients yet have not been included in prior COVID-19 seroepidemiology research in Nigeria. We sought to evaluate baseline seroprevalence, rates of seroconversion (IgG- to IgG+) and seroreversion (IgG+ to IgG-), change in IgG concentration at 3- and 6-month follow-up, and factors associated with seropositivity. From June 2020 to December 2020, we conducted a longitudinal seroepidemiology study among frontline health care workers in Nigeria using a validated dried blood spot assay. Among 525 participants, mean (SD) age was 39.1 (9.7) years, 61.0% were female, and 45.1% were community health workers. The six-month follow-up rate was 93.5%. Seropositivity rates increased from 31% (95% CI: 27%, 35%) at baseline to 45% (95% CI: 40%, 49%) at 3-month follow-up, and 70% (95% CI: 66%, 74%) at 6-month follow-up. There was a corresponding increase in IgG levels from baseline (median = 0.18 ug/mL) to 3-month (median = 0.35 ug/mL) and 6-month follow-up (median = 0.59 ug/mL, Ptrend < .0001). A minority of participants reported symptoms from February 2020 until baseline (12.2%) or during 3-month (6.6%) or 6-month (7.5%) follow-up. only 1 participant was hospitalized. This study demonstrated high baseline, 3-month and 6-month follow-up prevalence of IgG antibodies to SARS-CoV-2 during the first two waves of the COVID-19 pandemic in Nigeria among a cohort of unvaccinated frontline healthcare workers, including primary healthcare workers despite low symptomatology. These results may have implications in state- and national-level disease pandemic modeling. Trial registration: NCT04158154.

Human Infections with Borna Disease Virus 1 (BoDV-1) Primarily Lead to Severe Encephalitis: Further Evidence from the Seroepidemiological BoSOT Study in an Endemic Region in Southern Germany

More than 40 human cases of severe encephalitis caused by Borna disease virus 1 (BoDV-1) have been reported to German health authorities. In an endemic region in southern Germany, we conducted the seroepidemiological BoSOT study ("BoDV-1 after solid-organ transplantation") to assess whether there are undetected oligo- or asymptomatic courses of infection. A total of 216 healthy blood donors and 280 outpatients after solid organ transplantation were screened by a recombinant BoDV-1 ELISA followed by an indirect immunofluorescence assay (iIFA) as confirmatory test. For comparison, 288 serum and 258 cerebrospinal fluid (CSF) samples with a request for tick-borne encephalitis (TBE) diagnostics were analyzed for BoDV-1 infections. ELISA screening reactivity rates ranged from 3.5% to 18.6% depending on the cohort and the used ELISA antigen, but only one sample of a patient from the cohort with requested TBE diagnostics was confirmed to be positive for anti-BoDV-1-IgG by iIFA. In addition, the corresponding CSF sample of this patient with a three-week history of severe neurological disease tested positive for BoDV-1 RNA. Due to the iIFA results, all other results were interpreted as false-reactive in the ELISA screening. By linear serological epitope mapping, cross-reactions with human and bacterial proteins were identified as possible underlying mechanism for the false-reactive ELISA screening results. In conclusion, no oligo- or asymptomatic infections were detected in the studied cohorts. Serological tests based on a single recombinant BoDV-1 antigen should be interpreted with caution, and an iIFA should always be performed in addition.

Seroepidemiological Studies for the Detection of Antibodies against Seven Infectious Diseases in Old World Camels from Different Countries

Seroepidemiological Studies for the Detection of Antibodies against Seven Infectious Diseases in Old World Camels from Different Countries

Understanding the epidemiology of iNTS disease in Africa in preparation for future iNTS- vaccine studies in endemic countries: Seroepidemiology in Africa of iNTS (SAiNTS) Study Protocol: Malawi site [Version 9.0

Non-typhoidal Salmonella (NTS) are a major cause of bloodstream infections amongst children in sub-Saharan Africa. A clear understanding of the seroepidemiology and correlates of protection for invasive NTS (iNTS) in relation to key risk factors (malaria, anaemia, malnutrition) in children in Africa is needed to inform strategies for disease control including vaccine implementation. The SAiNTS study is a prospective community cohort study with paired serology samples from 2500 Malawian children 0-5 years at baseline and three months to measure age-stratified acquisition of lipopolysaccharide (LPS) O-antigen antibody (IgG) and serum bactericidal activity to the main serovars causing iNTS ( Salmonella Typhimurium and S. Enteritidis). Children are selected from mapped and censused randomly selected households in Chikwawa, Malawi; an area with substantial malaria burden. The sampling framework is set within a malaria vaccination (RTS,S/ AS01) phase 4 cluster randomized trial, known as the Epidemiology Study of Malaria Transmission Intensity (EPI-MAL), allowing exploration of the impact of malaria vaccination on acquisition of immunity to NTS. Risk factor data for invasive disease will be collected using rapid diagnostic tests for malaria and anaemia, anthropometry for malnutrition, and a validated questionnaire for indicators of socioeconomic status, water and sanitation. All data will be recorded through electronic case report forms using the REDCap and the Open Data Kit (ODK) platforms. Stool sample analysis includes NTS culture and pan-Salmonella polymerase chain reaction to assess enteric exposure and biomarkers of environmental enteric dysfunction. Cases with iNTS disease will be followed up for comparison with community controls. The final cohort of 2500 children will allow investigation into the impact of risk factors for iNTS on the acquisition of immunity in children 0-5 years in an endemic setting, including comparisons to partner seroepidemiology studies in three other sub-Saharan African sites (1000 children per site). The data generated will be key to informing iNTS disease control measures including targeted risk factor interventions and vaccine implementation through investigation of correlates of protection and identifying windows of immune susceptibility in at-risk populations.

Prevalence of SARS-CoV-2 infection and associated risk factors among asylum seekers living in asylum centres: A cross-sectional serologic study in Canton of Vaud, Switzerland

BackgroundUnderstanding the factors influencing SARS-CoV-2 transmission in asylum seekers and refugees living in centres is crucial to determine targeted public health policies protecting these populations fairly and efficiently. In response, this study was designed to explore the pandemic's spread into asylum centres during the first wave of the pandemic in Switzerland. Specifically, it aimed to identify the risk factors associated with a positive anti-SARS-CoV-2 seroprevalence test after the first semi-confinement period (16 March to 27 April 2020) amongst asylum seekers and refugees living in centres. MethodsThis research is part of SérocoVID, a seroepidemiologic study of SARS-CoV-2 infection conducted in the canton of Vaud, Switzerland. Migrants living in two asylum centres, one known to have had an epidemic outbreak, were invited to participate in this study. Anti-SARS-CoV-2 IgG and IgA antibodies targeting the spike viral protein were measured in all participants using a Luminex immunoassay. Each participant also completed a questionnaire measuring socio-demographic characteristics, medical history (comorbidities, smoking status, BMI, flu-like symptoms), health literacy, public health recommendations (wearing a masque in a public area, social distancing and hands cleaning), behaviours and exposures (daily life activities, number of contacts weekly). The association of these independent variables with the serologic test result were estimated using a multivariable logistic regression model. FindingsA total of 124 participants from the two asylum centres took part in the study (Centre 1, n = 82; Centre 2, n = 42). The mean participation rate was 36.7%. The seroprevalence in Centres 1 and 2 were 13% [95% CI 0.03, 0.14] and 50% [0.34, 0.65], respectively. Next, 40.63% of SARS-CoV-2 positive people never developed symptoms (asymptomatic cases), and no one had severe forms of the Covid-19 disease requiring hospitalisation. Participants report high compliance with public health measures, especially hygiene rules (96.3% of positive answers) and social distancing (88.7%). However, only 11.3% said they always wore a masque in public. After adjusting for individual characteristics, infection risk was lower amongst people with high health literacy (aOR 0.16, p = 0.007 [0.04, 0.60]) and smokers (aOR 0.20, p = 0.013 [0.06, 0.69]). ConclusionDespite the lack of severe complications of Covid-19 disease in this study, findings suggest that developing targeted public health measures, especially for the low health literacy population, would be necessary to limit the risk of outbreaks in asylum centres and improve this population's safety. Further investigations and qualitative approach are required to understand more finely how living conditions, risks and behaviours such as tobacco consumption, and the adoption of protective measures impact SARS-CoV-2 infection.

Seroepidemiological Survey of Lumpy Skin Disease among Cattle in El Gezira State (Central Sudan)

Lumpy skin disease (LSD) is an infectious viral disease that affects cattle, buffalos and selected wild animals. A cross-sectional study was conducted in El Gezira State, Central Sudan to determine the seroprevalence and risk factors of LSD in cattle in seven localities. A total of 197 serum samples were collected randomly from apparently healthy cattle during the period between April – May, 2021 and tested serologically with a commercial ELISA kit. The overall true seroprevalence of lumpy skin disease virus (LSDV) was 24.6% (50/198). Univariate analysis showed that there was a significant difference (p &lt; 0.05) in seropositivity to LSD between age groups, sex as well as breed. Multivariate analysis revealed that only two independent risk factors (age and breed) were statistically significant (p &lt; 0.05). It is apparent from the present study that LSDV infection is quite prevalent among cattle in El Gezira State, Central Sudan. To the best of the author’s knowledge, this is the first seroepidemiological study of LSDV infection in Central Sudan. The authors recommend that the concerned authorities expend more efforts to control this economically important disease in Sudan.

Serological Evaluation of Human Toxocariasis in Patients With Hypereosinophilia Referred to Tabriz Hospitals in Iran

Introduction: Toxocariasis is a parasitic infection that causes eosinophilia in humans. Infection in humans is created by swallowing parasite eggs through contaminated soil or hands. Then, the larvae exit from eggs in the small intestine and enter the bloodstream through the perforation of the intestine, and from there, they migrate to all various organs, leading to the creation of visceral larva migrans syndrome and ocular larva migrans syndrome. Methods: In this case study, a prospective study was performed on 100 patients who referred to these centers from February 2017 to January 2018 in different hospitals in Tabriz, in Iran. After the diagnosis of 50 hypereosinophilic patients (more than 10% eosinophilia) without a history of allergic disease as a case group and 50 patients without eosinophilia as a control group, we collected blood samples from these individuals and isolated their serum or plasma. Then, anti-Toxocara antibodies were measured by the enzyme-linked immunosorbent assay (ELISA) method in these patients. The data were analyzed by SPSS software. Results: The prevalence of anti-Toxocara antibodies was observed in 20% (10 patients) and 2% (1 patient) of hyperosinophils and controls, respectively. The mean age of the case and control groups was 22–75 years and 17–79 years, respectively, and 57% and 43% of the subjects were males and females. Conclusion: Seroepidemiological studies in Iran have shown a seroprevalence of the disease between 2% and 25.6%. Due to the fact that toxocariasis is caused by worm larvae, this disease can be diagnosed only by serological methods. Therefore, it is necessary to suspect toxocariasis in people with unspecified hypereosinophilia and perform an immunoserological test by the ELISA method. The findings demonstrated that this infection exists in the city of Tabriz.

Airport Personnel and Coronavirus Disease-2019: A Seroprevalence Study in Taiwan

Introduction Many countries tried to lifted the travel restriction to revive their stagnant tourism-based economies. However, infection risks among airport personnel are incompletely understood. We therefore conducted this seroepidemiological study targeting airport personnel. Methods This cross-sectional study was conducted from October 20th, 2020 to February 28th, 2021 at the Taoyuan International Airport in Taiwan. All adults who worked at Taoyuan International Airport and were older than 20-years of age were eligible for participation. Serological tests were collected and study participants were asked to complete an online questionnaire which collected self reported data including demographic characteristics, occupation, exposure risk assessment, recent symptoms, and self-perceived risk of infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Continuous data were expressed with median and interquartile ranges; categorical data were expressed with counts and proportions. Results A total of 450 volunteers agreed to participate in the study. Most of the participants worked as ground crew (40.7%). Approximately 43.6% of participants did not feel any symptoms in the 3-months prior to serologic testing. Only 8 participants (1.8%) reported close contact with confirmed coronavirus disease-2019 (COVID-19) cases. Overall, none of the study participants had serologic confirmation of immunoglobulin G (IgG) antibodies against SARS-CoV-2. Conclusion The SARS-CoV-2 infection rate among airport personnel was low. This study demonstrates that a well-designed border control strategy may work and so that transmission of SARS-CoV-2 may be controllable.

Socioeconomic differences in the reduction of face-to-face contacts in the first wave of the COVID-19 pandemic in Germany

BackgroundThe COVID-19 pandemic has led to physical distancing measures to control the spread of SARS-CoV-2. Evidence on contact dynamics in different socioeconomic groups is still sparse. This study aimed to investigate the association of socioeconomic status with private and professional contact reductions in the first COVID-19 wave in Germany.MethodsData from two especially affected municipalities were derived from the population-based cross-sectional seroepidemiological CORONA-MONITORING lokal study (data collection May–July 2020). The study sample (n = 3,637) was restricted to working age (18–67 years). We calculated the association of educational and occupational status (low, medium, high) with self-reported private and professional contact reductions with respect to former contact levels in the first wave of the pandemic. Multivariate Poisson regressions were performed to estimate prevalence ratios (PR) adjusted for municipality, age, gender, country of birth, household size, contact levels before physical distancing measures, own infection status, contact to SARS-CoV-2 infected people and working remotely.ResultsThe analyses showed significant differences in the initial level of private and professional contacts by educational and occupational status. Less private contact reductions with lower educational status (PR low vs. high = 0,79 [CI = 0.68–0.91], p = 0.002; PR medium vs. high = 0,93 [CI = 0.89–0.97], p = 0.001) and less professional contact reductions with lower educational status (PR low vs. high = 0,87 [CI = 0.70–1.07], p = 0.179; PR medium vs. high = 0,89 [CI = 0.83–0.95], p = 0.001) and lower occupational status (PR low vs. high = 0,62 [CI = 0.55–0.71], p < 0.001; PR medium vs. high = 0,82 [CI = 0.77–0.88], p < 0.001) were observed.ConclusionsOur results indicate disadvantages for groups with lower socioeconomic status in private and professional contact reductions in the first wave of the pandemic. This may be associated with the higher risk of infection among individuals in lower socioeconomic groups. Preventive measures that a) adequately explain the importance of contact restrictions with respect to varying living and working conditions and b) facilitate the implementation of these reductions especially in the occupational setting seem necessary to better protect structurally disadvantaged groups during epidemics.