This Week in Infectious Disease — Sep 4, 2026

Welcome to This Week in Infectious Disease. This week we're covering 10 notable papers spanning outbreak preparedness and filovirus response, drug safety and antimicrobial resistance, and prevention — from measles exposure management to nirsevimab rollout across Europe. Let's dive in.

We'll start with drug safety, because one paper this week deserves the attention of anyone who signs an order for intramuscular ceftriaxone. In Clinical Infectious Diseases, Pierce and colleagues report a multistate investigation launched after clusters of deaths were reported following ceftriaxone injections in late 2024. The Centers for Disease Control and Prevention issued a national call for cases, defining an event as death or cardiopulmonary resuscitation within six hours of a ceftriaxone injection in a non-intensive-care setting and not otherwise explained [1]. Thirty-one cases turned up across 18 states, most of them in outpatient facilities, and 12 of those patients died. What should catch your ear is the clinical picture. Roughly three quarters of the cases looked like anaphylaxis, but in about two thirds of those there was no skin or mucosal involvement at all — no urticaria, no angio-oedema, just cardiovascular collapse. Most patients had received ceftriaxone before, most had cardiac comorbidities, and the median age was 67. Two thirds were on antihypertensives, which plausibly blunts the compensatory response. Laboratory testing at the Food and Drug Administration found no tampering, no adulteration, no endotoxin, and no purity or potency problem, and national trend analyses using Medicare claims and adverse drug event surveillance showed no increase over the past decade. So the reassuring message is that there is no evidence of a bad batch or a new safety signal — but the practical message is that fatal reactions to a very commonly given drug do happen, that they can present without any rash, and that outpatient settings giving intramuscular ceftriaxone need resuscitation capability and an observation period. Report these to MedWatch.

Staying with antimicrobials, two papers address resistance from very different angles. In Antimicrobial Agents and Chemotherapy, Wiederhold and colleagues reviewed twenty years of azole susceptibility testing against Coccidioides at a reference laboratory, comparing the last decade with their previously published data [6]. The headline is stability: minimum inhibitory concentration distributions for fluconazole, itraconazole, posaconazole and voriconazole looked much the same across the two periods, with posaconazole the most potent agent and fluconazole showing consistently reduced susceptibility. Isavuconazole, newly represented, behaved like voriconazole. There were fluctuations in elevated values between 2011 and 2019, and importantly the correlation between fluconazole minimum inhibitory concentrations and those of the other azoles was weak — so a high fluconazole value does not predict failure of the newer triazoles. What we still lack is outcome data linking these laboratory numbers to how patients actually do. Meanwhile in the Journal of Antimicrobial Chemotherapy, Tickler and colleagues offer a hypothesis-generating argument about Clostridioides difficile ribotype 027 and related lineages [3]. Their hierarchical model puts fluoroquinolones as the dominant selective force behind the worldwide expansion of these epidemic strains, with rifampin and the rifamycins acting as secondary modifiers that shaped persistence and regional dominance. It is a proposal rather than a dataset, but it is a reminder that stewardship of drug classes we rarely associate with C. difficile may still be shaping its epidemiology.

The third theme this week is outbreak response, and The Lancet Infectious Diseases contributes two complementary papers on the 2026 Bundibugyo virus outbreak in the Democratic Republic of Congo. Andrews and colleagues built a stochastic transmission model on a household-community contact network, calibrated to outbreak data, to ask what a partially cross-protective vaccine would actually buy you [4]. The answer is sobering and clarifying. Strengthening the basics — raising case detection from about thirty to seventy percent and contact tracing from thirty to eighty percent, with isolation — cut expected mortality by around eighty percent on its own, with no vaccine at all. Layering reactive ring vaccination of contacts and contacts-of-contacts on top of those enhanced operations added only a further ten percent or so. Broad community vaccination produced the largest reductions, up to roughly eighty-seven percent at eighty percent coverage, but at a cost of between about fifty and one hundred and ten doses per death averted, compared with about thirty-five doses for ring vaccination under weaker operations. The practical implication is that for a vaccine of uncertain cross-protection, the population value depends principally on rapid and broad delivery, and that no vaccine substitutes for competent case finding and isolation. Alongside that, Best and colleagues tackled the diagnostic bottleneck [5]. The test deployed at the start of the outbreak was designed for Ebola virus, a distinct species, and no isolate of the outbreak strain was available. The group generated an inactivated, patient-derived genome reference standard from a throat swab, distributed it internationally, and analytically validated four real-time reverse-transcription polymerase chain reaction assays. The reference material was stable at four and twenty degrees for ninety hours, degrading meaningfully only at thirty-seven degrees. Bundibugyo-specific assays were roughly four times more sensitive than broad-range filovirus screens, and specificity testing across nine laboratories — against thirty pathogens and more than a hundred clinical samples per assay — was completed in fifteen days with no cross-reactivity. That is a model for how laboratory networks can bridge the gap between recognising an outbreak and having certified tests in hand.

Our fourth theme is prevention and the practical business of infection control. In PLOS Medicine, Lenglart and colleagues analysed more than one hundred thousand bronchiolitis presentations from 27 paediatric emergency departments across 12 European countries, using a controlled interrupted time-series design [8]. Reductions after nirsevimab introduction ranged from essentially nothing in some regions to a sixty-one percent drop in others, and that variability tracked almost perfectly with local nirsevimab coverage. Control countries showed flat bronchiolitis trends, and urinary tract infections — the control outcome — were unchanged, which argues against a generic post-pandemic drift. This is ecological data, so causality cannot be inferred, but the message for programme design is clear: the benefit of nirsevimab is delivered by implementation, not by efficacy alone. On the infection-control side, Askari and colleagues in Clinical Infectious Diseases reviewed New York City surveillance of over two thousand people exposed to 28 measles cases in healthcare facilities between December 2023 and September 2025 [2]. Not a single secondary case occurred — including among the ninety-five non-immune contacts who received no post-exposure prophylaxis. Two thirds of exposures happened in emergency departments or inpatient units, and roughly a quarter of contacts with known exposure timing were never in the room with the case at all, arriving within two hours after the patient left or was isolated. The authors argue that purely time-based exposure definitions may be too broad and that incorporating facility air-exchange data could target these very resource-intensive investigations more precisely.

Rounding out the week, two papers on chronic and conceptual questions. In the Journal of Antimicrobial Chemotherapy, Sempere and colleagues report DorSwitch, a prospective pilot in 13 virologically suppressed adults with documented historical non-nucleoside reverse transcriptase inhibitor resistance mutations who switched from etravirine to doravirine [9]. All evaluable participants stayed below fifty copies per millilitre through week 48, with no virological failures; doravirine had an equal or lower predicted resistance penalty than etravirine in eleven of thirteen, trough concentrations were as expected in those on darunavir with cobicistat, and total and LDL cholesterol fell significantly. This is thirteen carefully selected people, so it is hypothesis-generating, not practice-changing — but it supports formal evaluation. Nature Reviews Disease Primers published a comprehensive primer on varicella zoster virus, worth bookmarking for its emphasis on the reactivation syndromes that occur without rash or temporally dissociated from it — vasculopathy, cranial neuropathies, myelopathy — where diagnosis is genuinely hard, and on valacyclovir as the oral drug of choice [7]. And in The Lancet Infectious Diseases, Salomão and colleagues argue in a Personal View that lumping malaria, leptospirosis, tuberculosis and severe gastroenteritis under the sepsis umbrella distorts both burden estimates and therapeutic logic, since these illnesses follow different trajectories and demand disease-specific diagnostics [10]. They propose stratifying them as sepsis from an endemic or emerging infectious disease, to separate milder cases from those with organ dysfunction.

If you only have time for one paper this week, make it the ceftriaxone investigation in Clinical Infectious Diseases [1]. It concerns a drug nearly all of us prescribe, in outpatient settings where resuscitation resources are thin, and it reframes what a fatal reaction looks like.

Here are the key takeaways from this week in Infectious Disease. First, fatal anaphylaxis-type reactions to ceftriaxone occur, often without any skin or mucosal signs and often in patients previously exposed — ensure observation and resuscitation capacity wherever you give it, and report events to MedWatch. Second, in filovirus outbreak response, case detection, tracing and isolation avert most deaths; a partially protective vaccine adds value mainly through broad, rapid delivery, not ring strategies alone. Third, nirsevimab's real-world impact on bronchiolitis presentations is driven by coverage — implementation is the intervention. Fourth, measles exposure investigations in healthcare facilities based purely on the two-hour rule may be far broader than transmission risk warrants. And fifth, fluconazole susceptibility in Coccidioides remains reduced but stable over twenty years, and does not predict activity of the newer triazoles.

That's your roundup for This Week in Infectious Disease. The full transcript and references are available on the episode page in your AudioScholar library. This is an AI-curated summary — for clinical decisions, always consult primary sources and current guidelines. See you next week.

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This is an automated summary generated by artificial intelligence, which can make mistakes. Always review the original source materials.