Certain bacteria that normally live on the skin or in the nose without causing problems can sometimes lead to diseases elsewhere in the body. For example, the bacterium Staphylococcus aureus can cause blood infections or a severe and painful infection of the muscle called pyomyositis, which is very common in children who live in the tropics.

Scientists believe that pyomyositis happens when S. aureus bacteria in the blood stream infect the muscles. Some strains of this bacteria are more likely to cause such infections, but why is unclear. One potential cause is a toxin produced by some S. aureus bacteria called Panton-Valentine leucocidin (PVL). So far, studies looking at whether PVL-producing bacteria are more likely to cause pyomyositis have had conflicting results.

Now, Young et al. show that the gene for PVL is always present in S. aureus strains that cause pyomyosistis in Cambodian children, but is rarely found in S. aureus taken from the noses of their healthy counterparts. In the experiments, bacteria were collected from 101 children with pyomyositis and from the noses of 417 healthy children at the Angkor Hospital for Children in Cambodia over a 5-year period. The DNA in these bacteria were compared using very sensitive genetic techniques. The comparisons showed having the gene for PVL increased the odds of having pyomyositis 130-fold, showing that this one toxin likely accounts for much of the risk of developing this disease.

If more studies confirm the link between PVL and pyomyositis, developing vaccines that block the gene for PVL might be one way to protect children in the tropics from developing this infection. Treating children with pyomyositis with antibiotics that reduce the production of the PVL toxin may also be helpful.

Microbial genome sequencing and bacterial genome-wide association studies (GWAS) present new opportunities to discover bacterial genes involved in the pathogenesis of serious infections (Sheppard et al., 2013; Chewapreecha et al., 2014; Earle et al., 2016; Lees et al., 2016; Falush, 2016; Power et al., 2017). Pyomyositis is a severe infection of skeletal muscle most commonly seen in children in the tropics (Chauhan et al., 2004; Verma, 2016; Bickels et al., 2002). In up to 90% of cases, it is caused by a single bacterial pathogen, Staphylococcus aureus (S. aureus) (Chauhan et al., 2004; Verma, 2016; Bickels et al., 2002; Moriarty et al., 2015). Unlike infections of the skin and superficial soft tissues, the skin and subcutaneous tissues are not usually involved in pyomyositis, by contrast to intense inflammation in the infected muscles (Chauhan et al., 2004; Verma, 2016). Pyomyositis is thought to arise from haematogenous seeding of bacteria from blood to muscle (Verma, 2016). There is evidence that some S. aureus strains have heightened propensity to cause pyomyositis – the incidence in the USA doubled during an epidemic of community-associated methicillin resistant S. aureus (CA-MRSA) (Pannaraj et al., 2006) – but molecular genetic investigation of S. aureus from pyomyositis has been limited (Borges et al., 2012).

Panton–Valentine leucocidin (PVL), a well-known staphylococcal toxin causing purulent skin infections and found in epidemics caused by CA-MRSA, has been implicated in pyomyositis, pneumonia and other S. aureus disease manifestations, but its role in these invasive infections is disputed (Shallcross et al., 2013; Vandenesch et al., 2003; Labandeira-Rey et al., 2007; Villaruz et al., 2009). PVL is a bipartite pore-forming toxin comprising the co-expressed LukF-PV and LukS-PV proteins (Löffler et al., 2010; Boakes et al., 2011). The coding sequence for PVL, lukSF-PV, is usually carried on bacteriophages, (Shallcross et al., 2013; Löffler et al., 2010), which facilitate lukSF-PV exchange between lineages (McCarthy et al., 2012). The mechanism of PVL toxicity has been shown to involve cell lysis in human myeloid cells, particularly neutrophils, by insertion into the cellular membrane, (Niemann et al., 2018) leading the tissue to release inflammatory neutrophil products (Spaan et al., 2013). Neutrophil lysis is mediated by PVL binding to target complement receptors C5aR; in binding, PVL has both toxic and immunomodulatory effects, as it also inhibits C5a mediated immune activation (Sina et al., 2013).

Although small case series testing for candidate genes have reported a high prevalence of PVL among pyomyositis-causing S. aureus, (Pannaraj et al., 2006; Sina et al., 2013; García et al., 2013) a detailed meta-analysis found no evidence for an increased rate of musculoskeletal infection (or other invasive disease) in PVL-positive bacteria versus controls (Shallcross et al., 2013). These conflicting results may reflect insufficiently powered studies, and some case series lack comparative control strains (Sina et al., 2013). A further problem with the use of candidate gene studies in studying pathogenesis is that they may miss important variation elsewhere in the genome. One study reporting a critical role for PVL in the causation of severe pneumonia (Labandeira-Rey et al., 2007) was later found to have overlooked mutations in key regulatory genes, capable of producing the virulence that had been attributed to PVL by the original study (Villaruz et al., 2009). Thus, while some evidence suggests an association between pyomyositis and PVL, there remains significant uncertainty regarding the bacterial genetic predisposition of S. aureus to pyomyositis, and whether PVL is an important virulence factor, or merely an epiphenomenon, carried by bacteria alongside unidentified genetic determinants (Otto, 2011; Day, 2013).

GWAS offer a means to screen entire bacterial genomes to discover genes and genetic variants associated with disease risk. They are particularly appealing because they enable the investigation of traits not readily studied in the laboratory, and do not require the nomination of specific candidate genes (Falush, 2016). Proof-of-principle GWAS in bacteria have demonstrated the successful rediscovery of known antimicrobial resistance (AMR) determinants (Chewapreecha et al., 2014; Earle et al., 2016; Lees et al., 2016). However, AMR is under extraordinarily intense selection in bacteria. More subtle traits, including host specificity (Sheppard et al., 2013) and the duration of pneumococcal carriage, (Lees et al., 2017) have also been demonstrated using GWAS. Promising results for GWAS in human infecting bacteria include identifying possible loci for invasive infection with Streptococcus pyogenes (Lees et al., 2016) and Staphylococcus epidermidis (Méric et al., 2018),and the identification of virulence-associated genes corresponding with regional differences in disease manifestations of melioidosis (Chewapreecha et al., 2017). Within species, lineage-specific variants have been shown to predict mortality following S. aureus bacteraemia (Recker et al., 2017). These studies support the potential GWAS has to precisely pinpoint genes and genetic variants underlying the propensity to cause specific human infections, making it a promising tool to investigate the possible contribution of bacterial genomic variation to pyomyositis.

To understand the bacterial genetic basis of pyomyositis, we sampled and whole-genome sequenced S. aureus from 101 pyomyositis infections and 417 asymptomatic nasal carriage episodes in 518 children attending Angkor Hospital for Children in Siem Reap, Cambodia between 2008 and 2012 (Supplementary file 1). As expected, we observed representatives of multiple globally common lineages in Cambodia, together with some globally less common lineages at high frequency, in particular clonal complex (CC) 121, identified by multi-locus sequence typing (MLST). There were no major changes in lineage frequency over time (Figure 1—figure supplement 1).

In our study, some S. aureus lineages were strongly overrepresented among cases of pyomyositis compared with asymptomatic, nasally-carried controls over the same time period. Notably, 86/101 (85%) of pyomyositis cases were caused by CC-121 bacteria, whereas no pyomyositis cases were caused by the next two most commonly carried lineages, sequence type (ST)−834 and CC-45 (Figure 1). We estimated the overall heritability of case/control status to be 63.8% (95% CI 49.2–78.4%) in the sample, reflecting the strong relationship between bacterial genetic variation and case/control status. We used bugwas (Power et al., 2017) to decompose this heritability into the principal components (PCs) of bacterial genetic variation. PC 1, which distinguished CC-121 (the most common pyomyositis lineage) from ST-834 (which was only found in carriage), showed the strongest association with case/control status (p=10^-29.6, Wald test). The strongest association was with PC 20, which differentiated a sub-lineage of CC-121 within which no cases were seen (p=10^-13.9), and PC 2, which distinguished CC-45 from the rest of the species (p=10^-4.9).

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We conducted a GWAS to identify bacterial genetic variants associated with pyomyositis, controlling for differences in pyomyositis prevalence between S. aureus lineages. We used a kmer-based approach (Sheppard et al., 2013) in which every variably present 31 bp DNA sequence observed among the 518 genomes was tested for association with pyomyositis versus asymptomatic nasal carriage, controlling for population structure using GEMMA (Zhou and Stephens, 2012). These kmers captured bacterial genetic variation including single nucleotide polymorphisms (SNPs), insertions or deletions (indels), and presence or absence of entire accessory genes. We found 10.7 million unique kmers variably present across the bacterial genomes. In total, 9175 kmers were significantly associated with case/control status after correction for multiple testing (10^-6.8 ≤ p ≤ 10^-21.4; Figure 2A). When mapped to the de novo assembly of a CC121 isolate from pyomyositis (PYO2134), the vast majority of these kmers (9,074/9,175; 98.9%) localised to a 45.7 kb region spanning an integrated prophage with 95% nucleotide identity to φSLT (Figure 2B). Most (9,173/9,175; 99.98%) significant kmers were found at an increased frequently in pyomyositis, with odds ratios (OR) ranging from 2.7 to 139.8, indicating that the presence of each was associated with increased risk of disease. The presence of bacteriophage φSLT was thus strongly associated with pyomyositis.

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We were able to localise the most statistically significant signal of association to kmers that mapped within φSLT to the lukS-PV and lukF-PV cargo genes. These genes encode the subunits of PVL, which multimerise into a pore-forming toxin capable of rapidly lysing the membranes of human neutrophils (Löffler et al., 2010; Otto, 2011). 1630 kmers tagging the presence of the lukSF-PV coding sequences (CDS) were highly significantly associated with disease, being present in 98/101 (97%) pyomyositis cases and 84/417 (20%) carriage controls (unadjusted OR 129.5, p=10^-17.9). Kmers tagging variation in the 389 bp region immediately upstream of the CDS were also strongly associated with disease (p=10^-21.4). The most significant of these kmers were co-present with the CDS in the same cases (98/101, 97.0%), but present in fewer controls (79/417, 18.9%), producing an OR of 140.

Closer examination of this ~400 bp upstream region in genomes assembled from short-read Illumina sequencing showed that assembly of the region was problematic, with breaks or gaps in the assembly (Figure 2—figure supplement 2). To improve the accuracy of this region of the assembled genomes we performed long-read Oxford Nanopore sequencing on the 37 genomes with incomplete or discontinuous assembly upstream of the PVL CDS. By integrating long-read and short-read data we were able to assemble a single contig spanning this region in all isolates (Figure 2—figure supplement 2). When these improved assemblies were introduced, the signal of association upstream of the PVL CDS was no more significant than within the CDS (Figure 2C). Therefore, the presence of genomic sequence spanning the PVL toxin-coding sequences and the upstream, presumed regulatory, region exhibited the strongest association with pyomyositis in the S. aureus genome. All isolates with kmers mapping to the PVL CDS had 98% or more coverage for the PVL CDS genes in de novo assembly (Figure 2—figure supplement 3). The signal of association in the earlier and later periods of the study were examined and found to be consistent (Figure 2—figure supplement 4).

Out of 9175 kmers significantly associated with pyomyositis, we only found 101 kmers related to regions outside the PVL-carrying prophage (Figure 2A, Supplementary file 2). Two kmers mapping at a position near 0.2 Mb in the PYO2014 reference genome showed homology to platelet adhesin sraP by BLAST. Thirty-five kmers mapping to a 50 bp non-coding fragment at 0.6 Mb and two kmers mapping to 2.8 Mb showed homology to an MSSA476 intergenic sequence between adhesin-encoding sdrC and sdrD by BLAST. One kmer mapping to position 2.0 Mb showed no sequence homology by BLAST. Sixty-one kmers mapping to a 61 bp non-coding region at 2.7 Mb showed homology to an MSSA476 intergenic sequence between acetyltransferase-encoding genes SAS2453 and SAS2454 by BLAST. In conclusion, these other signals were short, fragmentary and mostly non-coding so we did not investigate them further.

The presence of high-risk kmers mapping to the PVL region explained the vast majority of observed heritability. When the presence or absence of the most significant kmer pattern, a set of kmers with an identical pattern of presence in the population, all of which mapped to the PVL region, was included as a covariate in GEMMA, the remaining heritability not explained by other factors was estimated and found to be 0.0% (95% CI 0–2.5%). Thus, the point estimate for heritability (not explained by the inclusion of PVL-tagging kmers) is reduced by 100% (95% CI 93.5–100%), meaning we have little evidence for any remaining heritability in case/control status.

Presence or absence of the PVL region accounted for the differences in pyomyositis rates between lineages. It was common in pyomyositis-associated lineages including CC-121 and absent from carriage/non-pyomyositis-associated lineages including ST-834 and CC-45 (Figure 1), explaining over 99.9% of observed heritability in case-control status. It was infrequent in the non-pyomyositis-associated sub-lineage of CC-121 (2/36, 5.6%), and sporadically present in pyomyositis cases in otherwise non-pyomyositis-associated, PVL-negative strains CC-1 and CC-88. Its absence from only three cases (in lineages CC-88, CC-1 and CC-121) suggested that the PVL region approached necessity for development of pyomyositis in the current setting in Cambodian children, while its presence in 20% of controls indicated that PVL-associated pyomyositis is incompletely penetrant, that is presence of the PVL region does not always lead to disease.

PVL genes were carried on multiple genetic backgrounds in this population, and the phage backgrounds vary by clonal complex. We examined all assemblies for sequence similarity to six known bacteriophages that carry the PVL genes, (Boakes et al., 2011) as well as the 45.7 kb region in PYO2134, a hypothesised integrated prophage identified in the reference genome prepared for this study, which we have called φCC121 (Figure 2—figure supplement 3). The finding of PVL genes on BLAST corresponded completely with the presence of kmers mapping across the PVL locus. We find sequences with >95% homology to four of these seven phages in the population. Regions in some assemblies showed homology for multiple phages, reflecting the similarity between jSLT, jSa2USA and jCC121 rather than the presence of multiple phages, and resolution of phages was limited by fragmented assemblies from short reads (Supplementary File 2B). Phage types were restricted within most lineages, with jSLT found in ST-3206, jSa2USA in ST-1232 and jPVL in CC-1. jCC121 was the phage most often identified in the dominant pyomyositis strain CC-121, but it was absent in all but one isolate from the low risk subclade within CC-121. Strikingly, PVL-negative isolates in CC-121 and ST-834 strains frequently retained sequence homologous to >95% of jSLT, suggesting that some PVL-negative CC-121 isolates lost PVL secondarily by gene deletion rather than prophage excision.

In this study, we found a strong association between pyomyositis, a highly distinctive tropical infection of skeletal muscle in children, and Panton-Valentine leukocidin, a bacterial toxin commonly carried by bacteriophages. We found that a single coding region together with the upstream sequence are all but necessary for the development of pyomyositis: its sporadic presence is associated with pyomyositis in otherwise low-frequency strains, and its absence is associated with asymptomatic carriage in a high-propensity strain. PVL appears to be carried on multiple phage backgrounds in this population, but PVL-positive lineages generally carry a single phage type, as expected given the observed strain restriction of phages in S. aureus (Xia and Wolz, 2014; Stegger et al., 2014). The locally common PVL-positive CC-121 lineage contributes most strongly to the prevalence of pyomyositis in Cambodian children.

While PVL has long been thought an important S. aureus virulence factor, (Diep et al., 2008; Bocchini et al., 2006; Kurt et al., 2013) its role in invasive disease has been controversial, (Otto, 2011; Day, 2013) with conflicting results in case-control studies and an absence of supporting evidence on meta-analysis (Shallcross et al., 2013). In previous studies, the PVL-positive USA300 lineage was associated with musculoskeletal infection (both pyomyositis and osteomyelitis), however in these studies almost all such infections were caused by the USA300 strain, so the role of PVL was almost completely confounded by both methicillin resistance and strain background (Pannaraj et al., 2006; Bocchini et al., 2006). In our study, this confounding influence is broken down by the movement of PVL on mobile genetic elements (MGEs). Despite the emergence of CA-MRSA in carriage in Cambodia (Nickerson et al., 2011), all the pyomyositis cases were MSSA (Figure 1—figure supplement 1). By applying a GWAS method to a well-powered cohort, our study resolves the controversy around pyomyositis and PVL, demonstrating strong heritability which localises to a single region, even when the full bacterial genome is considered. Bacterial GWAS can pinpoint virulence variants when MGEs act to unravel linkage disequilibrium, if effect sizes are sufficiently strong.

There is strong biological plausibility for the association demonstrated in this study. PVL is a well characterised S. aureus toxin, toxic to the myeloid cells that form a first line of defence against bacterial infection, (Oliveira et al., 2018) and, in binding to myeloid cells by a complement receptor (C5aR), exerts immunomodulatory effects (Spaan et al., 2013). The establishment of muscle abscesses is a critical step in the pathogenesis of pyomyositis, but unlike renal, hepatic and splenic abscesses, skeletal muscle abscesses are rarely observed in experimental models of bacteraemia, unless there is preceding muscle trauma (Miyake, 1904). S. aureus strains containing PVL show increased duration of bacteraemia in a rabbit model of sepsis, (Xia and Wolz, 2014) and result in larger muscle abscesses (Tseng et al., 2009). PVL has been found strongly bound to necrotic muscle in an individual with myositis associated with necrotizing fasciitis (Lehman et al., 2010). These observations support the hypothesis that PVL may facilitate bacterial seeding to muscles via the bloodstream and tropism for muscular infection.

These results establish that, for children in Cambodia, staphylococcal pyomyositis is a disease whose pathogenesis depends crucially on a single toxin. This property is shared by toxin-driven, vaccine-preventable diseases such as tetanus and diphtheria. Therefore, vaccines that generate neutralising anti-toxin antibodies against PVL (Landrum et al., 2017) might protect human populations specifically against this common tropical disease. These results also raise the hypothesis that antibiotics which decrease toxin expression, and have been recommended in some PVL-associated infections, (Saeed et al., 2018) may offer specific clinical benefit in treating pyomyositis. More generally, our study provides an example of how microbial GWAS can be used to elucidate the pathogenesis of bacterial infections and identify specific virulence genes associated with human disease.

Sequence data has been submitted to Short Read Archive (Bioproject ID PRJNA418899).

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Author details

1. Bernadette C Young

   1. Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
   2. NIHR Oxford Biomedical Research Centre, Infection Theme, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Oxford, United Kingdom

   Contribution

   Investigation, Visualization, Methodology, Writing—original draft, Writing—review and editing

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0001-6071-6770

2. Sarah G Earle

   Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom

   Contribution

   Data curation, Formal analysis, Methodology, Writing—review and editing

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0002-0738-7557

3. Sona Soeng

   Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia

   Contribution

   Investigation, Methodology

   Competing interests

   No competing interests declared

4. Poda Sar

   Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia

   Contribution

   Investigation, Methodology

   Competing interests

   No competing interests declared

5. Varun Kumar

   Department of Pediatrics, East Tennessee State University Quillen College of Medicine, Johnson City, United States

   Contribution

   Conceptualization, Writing—review and editing

   Competing interests

   No competing interests declared

6. Songly Hor

   Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia

   Contribution

   Investigation, Writing—review and editing

   Competing interests

   No competing interests declared

7. Vuthy Sar

   Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia

   Contribution

   Investigation, Writing—review and editing

   Competing interests

   No competing interests declared

8. Rachel Bousfield

   Department of Infectious Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom

   Contribution

   Data curation, Investigation, Writing—review and editing

   Competing interests

   No competing interests declared

9. Nicholas D Sanderson

   Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom

   Contribution

   Investigation, Methodology, Writing—review and editing

   Competing interests

   No competing interests declared

10. Leanne Barker

    Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom

    Contribution

    Investigation, Methodology, Writing—review and editing

    Competing interests

    No competing interests declared

11. Nicole Stoesser

    1. Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
    2. Public Health England Academic Collaborating Centre, John Radcliffe Hospital, Oxford, United Kingdom

    Contribution

    Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

12. Katherine RW Emary

    NIHR Oxford Biomedical Research Centre, Infection Theme, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Oxford, United Kingdom

    Contribution

    Conceptualization, Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

13. Christopher M Parry

    1. Clinical Sciences, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
    2. School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan

    Contribution

    Conceptualization, Investigation, Methodology, Writing—review and editing

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0001-7563-7282

14. Emma K Nickerson

    Department of Infectious Diseases, Cambridge University Hospitals NHS Foundation Trust, Cambridge, United Kingdom

    Contribution

    Investigation, Methodology, Writing—review and editing

    Competing interests

    No competing interests declared

15. Paul Turner

    1. Cambodia Oxford Medical Research Unit, Angkor Hospital for Children, Siem Reap, Cambodia
    2. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom

    Contribution

    Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0002-1013-7815

16. Rory Bowden

    Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom

    Contribution

    Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0001-8596-0366

17. Derrick W Crook

    1. Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
    2. NIHR Oxford Biomedical Research Centre, Infection Theme, Oxford University Hospitals NHS Foundation Trust, John Radcliffe Hospital, Oxford, United Kingdom
    3. Public Health England Academic Collaborating Centre, John Radcliffe Hospital, Oxford, United Kingdom

    Contribution

    Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0002-0590-2850

18. David H Wyllie

    1. Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
    2. Public Health England Academic Collaborating Centre, John Radcliffe Hospital, Oxford, United Kingdom
    3. The Jenner Institute Laboratories, University of Oxford, Oxford, United Kingdom

    Contribution

    Investigation, Writing—review and editing

    Competing interests

    No competing interests declared

19. Nicholas PJ Day

    Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom

    Contribution

    Conceptualization, Supervision, Writing—review and editing

    Competing interests

    No competing interests declared

20. Daniel J Wilson

    1. Nuffield Department of Medicine, Experimental Medicine Division, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
    2. Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
    3. Institute for Emerging Infections, Oxford Martin School, University of Oxford, Oxford, United Kingdom

    Contribution

    Resources, Supervision, Writing—original draft, Writing—review and editing

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0002-0940-3311

21. Catrin E Moore

    1. Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, United Kingdom
    2. Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand

    Contribution

    Conceptualization, Resources, Data curation, Formal analysis, Supervision, Funding acquisition, Investigation, Methodology, Writing—original draft, Project administration, Writing—review and editing

    For correspondence

    catrin.moore@ndm.ox.ac.uk

    Competing interests

    No competing interests declared

    "This ORCID iD identifies the author of this article:" 0000-0002-8639-9846

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