SARS-CoV-2 infections among asymptomatic individuals contributed to COVID-19 cases: A cross-sectional study among prospective air travelers from Ghana

BackgroundThe spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by asymptomatic individuals has been reported since the early stages of the coronavirus disease 2019 (COVID-19) outbreak in various parts of the world. However, there are limited data regarding SARS-CoV-2 among asymptomatic individuals in Ghana. The aim of the study was to use test data of prospective travelers from Ghana as a proxy to estimate the contribution of asymptomatic cases to the spread of COVID-19.MethodsThe study analyzed the SARS-CoV-2 PCR test data of clients whose purpose for testing was classified as “Travel” at the COVID-19 walk-in test center of the Noguchi Memorial Institute for Medical Research (NMIMR) from July 2020 to July 2021. These individuals requesting tests for travel generally had no clinical symptoms of COVID-19 at the time of testing. Data were processed and analyzed using Microsoft Excel office 16 and STATA version 16. Descriptive statistics were used to summarize data on test and demographic characteristics.ResultsOut of 42,997 samples tested at the center within that period, 28,384 (66.0%) were classified as “Travel” tests. Of these, 1,900 (6.7%) tested positive for SARS-CoV-2. The majority (64.8%) of the “Travel” tests were requested by men. The men recorded a SARS-CoV-2 positivity of 6.9% compared to the 6.4% observed among women. Test requests for SARS-CoV-2 were received from all regions of Ghana, with a majority (83.3%) received from the Greater Accra Region. Although the Eastern region recorded the highest SARS-CoV-2 positivity rate of 8.35%, the Greater Accra region contributed 81% to the total number of SARS-CoV-2 positive cases detected within the period of study.ConclusionOur study found substantial SARS-CoV-2 positivity among asymptomatic individuals who, without the requirement for a negative SARS-CoV-2 result for travel, would have no reason to test. These asymptomatic SARS-CoV-2-infected individuals could have traveled to other countries and unintentionally spread the virus. Our findings call for enhanced tracing and testing of asymptomatic contacts of individuals who tested positive for SARS-CoV-2

Submicroscopic placental infection by non-<i>falciparum Plasmodium</i> spp.

<div><p>Background</p><p>Among the <i>Plasmodium</i> species that infect humans, adverse effects of <i>P</i>. <i>falciparum</i> and <i>P</i>. <i>vivax</i> have been extensively studied and reported with respect to poor outcomes particularly in first time mothers and in pregnant women living in areas with unstable malaria transmission. Although, other non-<i>falciparum</i> malaria infections during pregnancy have sometimes been reported, little is known about the dynamics of these infections during pregnancy.</p><p>Methods and findings</p><p>Using a quantitative PCR approach, blood samples collected from Beninese pregnant women during the first antenatal visit (ANV) and at delivery including placental blood were screened for <i>Plasmodium</i> spp. Risk factors associated with <i>Plasmodium spp</i>. infection during pregnancy were assessed as well as the relationships with pregnancy outcomes.</p><p><i>P</i>. <i>falciparum</i> was the most prevalent <i>Plasmodium</i> species detected during pregnancy, irrespective either of parity, of age or of season during which the infection occurred. Although no <i>P</i>. <i>vivax</i> infections were detected in this cohort, <i>P</i>. <i>malariae</i> (9.2%) and <i>P</i>. <i>ovale</i> (5.8%) infections were observed in samples collected during the first ANV. These non-<i>falciparum</i> infections were also detected in maternal peripheral blood (1.3% for <i>P</i>. <i>malariae</i> and 1.2% for <i>P</i>. <i>ovale</i>) at delivery. Importantly, higher prevalence of <i>P</i>. <i>malariae</i> (5.5%) was observed in placental than peripheral blood while that of <i>P</i>. <i>ovale</i> was similar (1.8% in placental blood). Among the non-<i>falciparum</i> infected pregnant women with paired peripheral and placental samples, <i>P</i>. <i>malariae</i> infections in the placental blood was significantly higher than in the peripheral blood, suggesting a possible affinity of <i>P</i>. <i>malariae</i> for the placenta. However, no assoctiation of non-<i>falciparum</i> infections and the pregnancy outcomes was observed</p><p>Conclusions</p><p>Overall this study provided insights into the molecular epidemiology of <i>Plasmodium</i> spp. infection during pregnancy, indicating placental infection by non-<i>falciparum Plasmodium</i> and the lack of association of these infections with adverse pregnancy outcomes.</p></div

Risk factors for <i>P</i>. <i>falciparum</i> malaria infections at enrolment.

<p>Risk factors for <i>P</i>. <i>falciparum</i> malaria infections at enrolment.</p

Association of <i>Plasmodium</i> spp. infections at enrolment with pregnancy outcomes.

<p>Association of <i>Plasmodium</i> spp. infections at enrolment with pregnancy outcomes.</p

Risk factors for <i>P</i>. <i>falciparum</i> and non-<i>falciparum</i> malaria mixed infections at enrolment.

<p>Risk factors for <i>P</i>. <i>falciparum</i> and non-<i>falciparum</i> malaria mixed infections at enrolment.</p

Parasite load of infections detected by microscopy and PCR.

<p>Parasite load of infections detected by microscopy and PCR.</p

Paired peripheral and placental samples of mono-infection of <i>P</i>. <i>malariae</i>.

<p>Paired peripheral and placental samples of mono-infection of <i>P</i>. <i>malariae</i>.</p

Association of <i>Plasmodium</i> spp. infections at delivery with pregnancy outcomes.

<p>Association of <i>Plasmodium</i> spp. infections at delivery with pregnancy outcomes.</p

Risk factors for <i>P</i>. <i>falciparum</i> malaria infections at delivery.

<p>Risk factors for <i>P</i>. <i>falciparum</i> malaria infections at delivery.</p

Monthly prevalence of <i>P</i>. <i>falciparum</i> and non-<i>falciparum</i> infections in Beninese pregnant women.

<p>The prevalence of <i>P</i>. <i>falciparum</i> (in red) and non-<i>falciparum</i> (in blue) infections detected in pregnant at the enrollment (A) and at delivery in the peripheral (B) and placental (C) blood samples are presented. Periods covered June 2008 to February 2010 corresponding to the recruitment of the pregnant women and October 2008 to August 2010 for the data collection at delivery.</p