Scrub typhus and the rickettsial diseases represent some of the oldest recognized vector-transmitted diseases, fraught with a rich historical aspect, particularly as applied to military/wartime situations. The vectors of Orientia tsutsugamushi were once thought to be confined to an area designated as the Tsutsugamushi Triangle. However, recent reports of scrub typhus caused by Orientia species other than O. tsutsugamushi well beyond the limits of the Tsutsugamushi Triangle have triggered concerns about the worldwide presence of scrub typhus. It is not known whether the vectors of O. tsutsugamushi will be the same for the new Orientia species, and this should be a consideration during outbreak/surveillance investigations. Additionally, concerns surrounding the antibiotic resistance of O. tsutsugamushi have led to considerations for the amendment of treatment protocols, and the need for enhanced public health awareness in both the civilian and medical professional communities. In this review, we discuss the history, outbreaks, antibiotic resistance, and burgeoning genomic advances associated with one of the world’s oldest recognized vector-borne pathogens, O. tsutsugamushi.

Background SARS-CoV-2 epidemiology implicates airborne transmission; aerosol infectiousness and impacts of masks and variants on aerosol shedding are not well understood. Methods We recruited COVID-19 cases to give blood, saliva, mid-turbinate and fomite (phone) swabs, and 30-minute breath samples while vocalizing into a Gesundheit-II, with and without masks at up to two visits two days apart. We quantified and sequenced viral RNA, cultured virus, and assayed sera for anti-spike and anti-receptor binding domain antibodies. Results We enrolled 49 seronegative cases (mean days post onset 3.8 ±2.1), May 2020 through April 2021. We detected SARS-CoV-2 RNA in 45% of fine (≤5 µm), 31% of coarse (>5 µm) aerosols, and 65% of fomite samples overall and in all samples from four alpha-variant cases. Masks reduced viral RNA by 48% (95% confidence interval [CI], 3 to 72%) in fine and by 77% (95% CI, 51 to 89%) in coarse aerosols; cloth and surgical masks were not significantly different. The alpha variant was associated with a 43-fold (95% CI, 6.6 to 280-fold) increase in fine aerosol viral RNA, compared with earlier viruses, that remained a significant 18-fold (95% CI, 3.4 to 92-fold) increase adjusting for viral RNA in saliva, swabs, and other potential confounders. Two fine aerosol samples, collected while participants wore masks, were culture-positive. Conclusion SARS-CoV-2 is evolving toward more efficient aerosol generation and loose-fitting masks provide significant but only modest source control. Therefore, until vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.

Rickettsial diseases and scrub typhus constitute a group of the oldest known vector-borne diseases. The cosmopolitan distribution of the vectors that transmit rickettsiae and orientiae leads to a worldwide prevalence of these diseases. Despite their significant historical status, detection and diagnosis of these diseases are still evolving today. Serological methods remain among the most prevalent techniques used for the detection/diagnosis of rickettsial diseases and scrub typhus. Molecular techniques have been instrumental in increasing the sensitivity/specificity of diagnosis, identifying new Rickettsia and Orientia species and have enhanced epidemiological capabilities when used in combination with serological methods. In this review, we discuss these techniques and their associated pros and cons.

Background: SARS-CoV-2 epidemiology implicates airborne transmission; mask source-control efficacy for, variant impact on, and infectiousness of aerosols are not well understood. Methods: We recruited COVID-19 cases to give blood, saliva, mid-turbinate and fomite (phone) swabs, and 30-minute breath samples while vocalizing into a Gesundheit-II, with and without masks at up to two visits two days apart. We quantified and sequenced viral RNA, cultured virus, and assayed sera for anti-spike and anti-receptor binding domain antibodies. Results: We enrolled 61 participants with active infection, May 2020 through April 2021. Among 49 seronegative cases (mean days post onset 3.8 ±2.1), we detected SARS-CoV-2 RNA in 45% of fine (≥5 μm), 31% of coarse (>5 μm) aerosols, and 65% of fomite samples overall and in all samples from four alpha variant cases. Masks reduced viral RNA by 48% (95% confidence interval [CI], 3 to 72%) in fine and by 77% (95% CI, 51 to 89%) in coarse aerosols. The alpha variant was associated with a 43-fold (95% CI, 6.6 to 280-fold) increase in fine aerosol viral RNA that remained a significant 18-fold (95% CI, 3.4 to 92-fold) increase adjusting for viral RNA in saliva, in mid-turbinate swabs, and other potential confounders. Two fine aerosol samples, collected days 2-3 post illness onset, while participants wore masks, were culture-positive. Conclusion: SARS-CoV-2 is evolving toward more efficient airborne transmission and loose-fitting masks provide significant but only modest source control. Therefore, until vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.

Whole blood lactate concentration is widely used in shock states to assess perfusion. We aimed to determine if the change in plasma renin concentration over time would be superior to the change in lactate concentration for predicting in-hospital mortality in hypotensive patients on vasopressors.

Three novel isolates of the genus Bartonella were recovered from the blood of two patients enrolled in a clinical trial for the treatment of chronic stage Bartonella bacilliformis infection (verruga peruana) in Caraz, Ancash, Peru. The isolates were initially characterized by sequencing a fragment of the gltA gene, and found to be disparate from B. bacilliformis. The isolates were further characterized using phenotypic and genotypic methods, and found to be genetically identical to each other for the genes assessed, but distinct from any known species of the genus Bartonella, including the closest relative B. bacilliformis. Other characteristics of the isolates, including their morphology, microscopic and biochemical properties, and growth patterns, were consistent with members of the genus Bartonella. Based on these results, we conclude that these three isolates are members of a novel species of the genus Bartonella for which we propose the name Bartonella ancashensis sp. nov. (type strain 20.00T = ATCC BAA-2694T = DSM 29364T).

A recently described clinical isolate, "Candidatus Bartonella ancashi," was obtained from a blood sample of a patient presenting with verruga peruana in the Ancash region of Peru. This sample and a second isolate obtained 60 days later from the same patient were molecularly typed using multilocus sequence typing (MLST) and multispacer sequence typing (MST). The isolates were 100% indistinguishable from each other but phylogenetically distant from Bartonella bacilliformis and considerably divergent from other known Bartonella species, confirming their novelty.

Orientia tsutsugamushi, formerly Rickettsia tsutsugamushi, is an obligate intracellular pathogen that causes scrub typhus, an underdiagnosed acute febrile disease with high morbidity. Scrub typhus is transmitted by the larval stage (chigger) of Leptotrombidium mites and is irregularly distributed across endemic regions of Asia, Australia and islands of the western Pacific Ocean. Previous work to understand population genetics in O. tsutsugamushi has been based on sub-genomic sampling methods and whole-genome characterization of two genomes. In this study, we compared 40 genomes from geographically dispersed areas and confirmed patterns of extensive homologous recombination likely driven by transposons, conjugative elements and repetitive sequences. High rates of lateral gene transfer (LGT) among O. tsutsugamushi genomes appear to have effectively eliminated a detectable clonal frame, but not our ability to infer evolutionary relationships and phylogeographical clustering. Pan-genomic comparisons using 31 082 high-quality bacterial genomes from 253 species suggests that genomic duplication in O. tsutsugamushi is almost unparalleled. Unlike other highly recombinant species where the uptake of exogenous DNA largely drives genomic diversity, the pan-genome of O. tsutsugamushi is driven by duplication and divergence. Extensive gene innovation by duplication is most commonly attributed to plants and animals and, in contrast with LGT, is thought to be only a minor evolutionary mechanism for bacteria. The near unprecedented evolutionary characteristics of O. tsutsugamushi, coupled with extensive intra-specific LGT, expand our present understanding of rapid bacterial evolutionary adaptive mechanisms.