Understanding the perspective of users and stakeholders.

To produce new digital diagnostics that will be widely used, it is important to understand the perspectives of all stakeholders involved in and impacted by their implementation. Understanding the perspectives of patients and healthcare workers is important, but consideration must also be given to the broader health system, government organisations, the commercial sector, international funders, and policy makers. This may start with mapping who the stakeholders are, identifying their needs, discussing their expectations for a new diagnostic, and engaging them throughout product design, development and evaluation in a codesign process.</p

Translation of molecular detection towards point-of-care digital diagnostics.

Translation of molecular detection towards point-of-care digital diagnostics.</p

Contrasting access to healthcare and diagnostics between low-resourced SSA settings and highly resourced healthcare settings.

In countries with highly resourced health systems, most of the population have easy access to health care services, often through multiple different routes. A wide range of diagnostic tests can be accessed through most healthcare providers, even if the samples need to be sent elsewhere for analysis. Strong infrastructure allows rapid transport, testing, and feedback of results, and diagnostic information can be shared between providers and patients with relative ease. Healthcare providers are often highly skilled and able to interpret the results of many different tests. In contrast, access to healthcare facilities and skilled healthcare workers in SSA is more heterogeneous and often limited, sometimes involving long journeys or incurring high costs to patients and their families. In rural and remote areas, the only accessible healthcare may be delivered by less skilled community healthcare workers, equipped with a limited range of point-of-care diagnostic tests. Healthcare facilities with high-quality laboratories do exist, but their capacity and the infrastructure to transport samples from distant facilities to these laboratories and return results in a timely fashion is often insufficient for the needs of the population, and results in further gaps in their linkage to appropriate and timely patient care. SSA, sub-Saharan Africa.</p

What is a digital molecular diagnostic?

Throughout this article, the term “digital molecular diagnostic” describes a small electronic device, providing a sample-to-answer solution to a diagnostic problem, in a portable, easy-to-use, robust, and cheap format. Any processing of a biological sample would ideally be integrated into the device, before allowing quantitative detection of the molecules used to make the diagnosis. The molecules detected are typically nucleic acids (DNA or RNA), but could also include proteins, or small chemical molecules. Such digital diagnostics will often use lab-on-chip technology, with their defining features being the generation, processing, and storage of data. Signals from the detection of molecules undergo processing within the device, so that actionable results are reported to the user without the need for further analysis. Results may be displayed on the device itself, or linked to other interfaces such as smartphones, and decision support may be integrated. Quantitative data generated by the device can be easily and immediately transmitted to facilitate patient care and contribute to disease surveillance.</p

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Table A: Names and affiliations of The Digital Diagnostics for Africa Network Contributors. Table B: Author contributions (CRediT Taxonomy). (DOCX)</p

A roadmap for digital molecular diagnostic development.

The development of new diagnostics is not linear, although it can be imagined as a progressive and staged process. At the outset, the current gaps and needs should be assessed and use cases developed. Context-appropriate TPPs should be developed in partnership with the potential users. Desirability (will people want to use it?), feasibility (is it technically possible?), viability (what is affordable?), and sustainability (long-term funding, readiness of and integration into the health system) should also be considered from the start of development. Prototype devices meeting the TPP are tested and refined through an iterative codevelopment and codesign process with users and an increasing number of other stakeholders who influence the diagnostic ecosystem. To bridge from prototype to implementation, scalability must be addressed, regulatory approvals gained, and continuous evaluation should ensure sustainable business models and compatibility with the evolving digital infrastructure. TPP, target product profile.</p

Current and future diagnostics in the integrated management of childhood febrile illness.

One of the most common and important diagnostic challenges in SSA is the management of fever in young children. WHO recommends that primary healthcare workers in resource-limited settings use a syndromic approach for managing childhood febrile illness, incorporating a mRDT in malaria endemic countries (current situation, pink area). Initial management involves a triage step to establish if the child is seriously ill, based on clinical danger signs; if these are present, the child is given antimalarial treatment, antibiotics, and referred urgently to a facility where additional diagnostic tests and treatments are available. If a child is not seriously ill, then a mRDT is performed and, if positive, the child is treated with antimalarials. If the mRDT is negative, the child is evaluated for clinical signs indicating a bacterial infection (there are currently no RDTs to confirm this at the point of care) and receives antibiotics if these are present. If symptoms are persistent, then the child is referred to a higher-level facility for further assessment. Many new diagnostics and decision support tools are currently being developed to improve outcomes by addressing weaknesses at each stage in this process (grey track). Additional diagnostics are in development to improve the speed or accuracy of diagnosis in the referral healthcare facilities with clinical laboratories. New digital molecular diagnostic devices (green track) have the potential to integrate accurate diagnosis, evaluation of severity, and decision support in a single device and, through modular design of diagnostic cartridges, could provide solutions throughout the patient journey. Connectivity means that data can be shared between facilities to support patient care and for public health decision-making. mRDT, malaria rapid diagnostic test; RDT, rapid diagnostic test.</p

DataSheet_1_‘Bouncing Back’ From Subclinical Malaria: Inflammation and Erythrocytosis After Resolution of P. falciparum Infection in Gambian Children.docx

Recent malaria is associated with an increased risk of systemic bacterial infection. The aetiology of this association is unclear but malaria-related haemolysis may be one contributory factor. To characterise the physiological consequences of persistent and recently resolved malaria infections and associated haemolysis, 1650 healthy Gambian children aged 8–15 years were screened for P. falciparum infection (by 18sRNA PCR) and/or anaemia (by haematocrit) at the end of the annual malaria transmission season (t1). P. falciparum-infected children and children with moderate or severe anaemia (haemoglobin concentration 2). Persistently infected children (PCR positive at t1 and t2) had stable parasite burdens and did not differ significantly haematologically or in terms of proinflammatory markers from healthy, uninfected children. However, among persistently infected children, IL-10 concentrations were positively correlated with parasite density suggesting a tolerogenic response to persistent infection. By contrast, children who naturally resolved their infections (positive at t1 and negative at t2) exhibited mild erythrocytosis and concentrations of pro-inflammatory markers were raised compared to other groups of children. These findings shed light on a ‘resetting’ and potential overshoot of the homeostatic haematological response following resolution of malaria infection. Interestingly, the majority of parameters tested were highly heterogeneous in uninfected children, suggesting that some may be harbouring cryptic malaria or other infections.</p

Additional file 1 of Modelling upper respiratory viral load dynamics of SARS-CoV-2

Additional file 1: Supplementary Table S1. Summary of studies which were identified during the literature search but did not provide viral load data when the corresponding authors were contacted. Studies included both male and female patients, unless stated. All ages stated are in years. *For some studies, particularly those carried out early in the pandemic, patients were hospitalised to ensure isolation (i.e. cohorts may include asymptomatic subjects or those with very mild symptoms). † These studies were identified during our literature search, but we were informed by the study authors that quantitative viral load was not available (i.e. only positive or negative result recorded). Supplementary Table S2. Summary of antiviral and immunomodulatory treatment in the studies included in analysis. Supplementary Table S3. Summary of the population-level (i.e. not study- or patient-specific) parameter values (and 95% credible intervals) obtained for the multi-level regression modelling (as displayed in Fig. 2). Patient- and study-specific random effects were used for both the peak (log-transformed) viral load, and its rate of decline per day. Supplementary Table S4. assessing the goodness of fit of the regression models using leave-one-out cross-validation. Supplementary Table S5. Summary of the population-level (i.e. not study- or patient-specific) parameter values (and 95% credible intervals) obtained for the mechanistic viral load model (Eqs. 6–8). Samples from k a 0 $${k}_a^0$$ and I max 0 $${I}_{\mathrm{max}}^0$$ were used to generate the black line and dark grey shaded area in Fig. 4. Supplementary Figure S1. Standard curves relating cycle-threshold (Ct) values to viral load. Seven standard curves, identified from published studies (see Methods) are plotted. Supplementary Figure S2. Summary of all the data collected (see Table 1 in the main text). For the studies shown in blue, viral loads have been estimated using an averaged standard curve (see Methods for details). Supplementary Figure S3 Comparison of timing of first sample and viral load by severity. Supplementary Figure S4. Estimations of the statistical power in the regression analyses. Supplementary Figure S5. Relationship between patient-specific parameters governing the immune response in the mechanistic model and disease severity. Supplementary Figure S6. Posterior means and 95% credible intervals for the study-specific offsets in the mechanistic model. Supplementary Figure S7. A comparison of the prior and posterior distributions for the early and late immune responses in the mechanistic model. Supplementary Figure S8. (shown over the following 7 pages): Output from the mechanistic model alongside the data, for all 155 patients considered. In the heading of each panel, the first number indicates the study (studies numbered as in Table 1)

Potent Virustatic Polymer–Lipid Nanomimics Block Viral Entry and Inhibit Malaria Parasites In Vivo

Infectious diseases continue to pose a substantial burden on global populations, requiring innovative broad-spectrum prophylactic and treatment alternatives. Here, we have designed modular synthetic polymer nanoparticles that mimic functional components of host cell membranes, yielding multivalent nanomimics that act by directly binding to varied pathogens. Nanomimic blood circulation time was prolonged by reformulating polymer–lipid hybrids. Femtomolar concentrations of the polymer nanomimics were sufficient to inhibit herpes simplex virus type 2 (HSV-2) entry into epithelial cells, while higher doses were needed against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given their observed virustatic mode of action, the nanomimics were also tested with malaria parasite blood-stage merozoites, which lose their invasive capacity after a few minutes. Efficient inhibition of merozoite invasion of red blood cells was demonstrated both in vitro and in vivo using a preclinical rodent malaria model. We envision these nanomimics forming an adaptable platform for developing pathogen entry inhibitors and as immunomodulators, wherein nanomimic-inhibited pathogens can be secondarily targeted to sites of immune recognition