I finished a wonderful novel last week; among other things, it reminded me of the beauty, complexity, and destructive forces in nature, certainly applicable to infections, pathogens, and vectors of disease.
The past week saw more publications than I could cover in depth (or that readers could tolerate, probably), so I had to narrow things down even more than I usually do. If you're feeling particularly adventuresome, some of the topics I excluded pertain to a new phase I Chlamydia vaccine trial that could prove to be a breakthrough eventually, more advice on use of the new pentavalent meningococcal vaccine, an in vitro study suggesting nasal epithelial properties account for less severe covid disease in children, and a tularemia outbreak in Utah beavers. I also left out the growing Salmonella outbreak linked to organic basil, though I did alert one of my sons who often shops at a store featuring the tainted product. Here's what made the cut this week.
Respiratory Disease Transmission is Not Binary
Most things in biology and medicine aren't binary, even if we tend to reduce our thinking to that level to simplify things. For example, most lab tests aren't just positive or negative, even though they are reported that way. The cutoff between those two choices are made to maximize specificity and sensitivity of the tests, but they don't necessarily work for all circumstances.
The World Health Organization provided an important new proposal for changing our longstanding terminology for spread of respiratory infections as either droplet or aerosol (airborne). It's just not that simple, as SARS-CoV-2 painfully taught us. I found I couldn't improve on WHO's explanation of the complexity of pathogen transmission through the air, so here it is verbatim with some highlights in red that are mine:
The following descriptors and stages have been defined by this extensively discussed consultation
to characterize the transmission of pathogens through the air (under typical circumstances):
- Individuals infected with a pathogen, during the infectious stage of the disease (the source), can generate particles containing the pathogen, along with water and respiratory secretions. Such particles are herein described as potentially ‘infectious particles’.
- These potentially infectious particles are carried by expired airflow, exit the infectious person’s mouth/nose through breathing, talking, singing, spitting, coughing or sneezing and enter the surrounding air. From this point, these particles are known as ‘infectious respiratory particles’ or IRPs.
- IRPs exist in a wide range of sizes (from sub-microns to millimetres in diameter). The emitted IRPs are exhaled as a puff cloud (travelling first independently from air currents and then dispersed and diluted further by background air movement in the room).
- IRPs exist on a continuous spectrum of sizes, and no single cut off points should be applied to distinguish smaller from larger particles, this allows to move away from the dichotomy of previous terms known as ‘aerosols’ (generally smaller particles) and ‘droplets’ (generally larger particles).
- Many environmental factors influence the way IRPs travel through air, such as ambient air temperature, velocity, humidity, sunlight (ultraviolet radiation), airflow distribution within a space, and many other factors, and whether they retain viability and infectivity upon reaching other individuals.
WHO still proposes a somewhat binary system of IRP spread, with "airborne transmission/inhalation" denoting pathogens which can spread at both short and longer distances, depending on various factors, versus "direct deposition," e.g. someone sneezes on you. It still may be confusing, but this is an important attempt to get past somewhat misleading advice such as a establishing a standard 6-foot distance between persons waiting in line.
Children and Adolescents Likely Still Benefit From Covid Vaccination
CDC has an update on covid vaccine effectiveness and durability, looking at the original monovalent vaccines over the time period from mid-December 2021 to late October 2023. Two doses of vaccine were 52% (95% CI 33%-66%) effective against hospitalization in the 5 - 18 year-old age group if vaccines were received no more than 4 months prior to hospitalization. From 4 to 12 months, protection against hospitalization waned significantly to 19% (95% CI 2%-32%). The report doesn't mention children less than 5 years of age, I suspect because vaccine authorization occurred later, numbers vaccinated are too small, and hospitalization was too uncommon to give reliable numbers.
Vaccine Adverse Events: New Numbers and a Terrific Interactive Web Site
The National Academies of Science, Engineering, and Medicine published new reports on adverse events from covid vaccines as well as an assessment of shoulder injuries from all vaccine administrations. The reports are excellent, but I fell in love with their web site. The NASEM group used levels of evidence to summarize current knowledge about various vaccine adverse events. The categories are evidence that a) establishes a causal relationship; b) favors acceptance of a causal relationship; c) inadequate to accept or reject a causal relationship; or d) favors rejection of a causal relationship. (Certainly this is far from a binary categorization!)
For covid vaccination they looked at six categories of adverse events: cardiac and vascular, female infertility, hearing conditions, immune-mediated events, neurologic events, and sudden deaths. The interactive web site allows you to pick and choose among various topics and subtopics and vaccines. Here's what the portion on myocarditis looks like:
Here's a look at acute biceps tendinopathy from vaccine administration in general:
You can also access the pdf version of the report (note it is a pre-publication proof, could contain some typos) to look at the summary and/or more details.
A Significant Change for Syphilis Screening From ACOG
I'm thrilled to see new recommendations for syphilis screening of pregnant people from the American College of Obstetricians and Gynecologists. I feel like my practice is a congenital syphilis quagmire right now. This updated recommendation gets away from the risk-based approach for screening which has always been a bit vague and clearly less useful with the resurgence of syphilis in the US. Now, every pregnant person should have syphilis testing 3 times: at the first prenatal visit, during the third trimester, and at birth. Previously a pregnant person with good prenatal care could escape with being screened only once early in pregnancy, a practice that would miss recent infection or infection acquired later in pregnancy. They also remind us that 40% of congenital syphilis occurs in infants whose mothers did not receive prenatal care; syphilis screening should be considered for pregnant people at every interaction with the healthcare system, such as emergency or urgent care visits.
Fake News From USDA?
Because of the avian flu concerns in the US, I've been trying for the first time to use alerts from the US Department of Agriculture on the status of avian influenza in wildlife and domesticated animals, including the recent importance of dairy animals. So far the alerts aren't telling me much, just clogging my in box with unhelpful information. So, I was a bit dismayed to see a recent NY Times article criticizing USDA transparency. Unfortunately the article requires a subscription, but it mentions an "obscure" USDA update (that I didn't receive) mentioning influenza A H5N1 further spreading among dairy cow herds and from there to poultry. More distressing to me is a claim in the Times article stating that asymptomatic infections have been discovered in a herd, but not yet reported by USDA; this is important since screening advice for dairy farmers currently is focused on symptoms in the cattle, with no screening of healthy-appearing cows. Perhaps USDA hasn't reported this asymptomatic infection possibility because it hasn't been verified, but one hopes they will be more transparent (and provide better updates) than they have so far. CDC learned a lot about public communication and transparency during the covid pandemic that should inform communications from USDA and other government agencies that we depend on.
Measles
Only 4 new cases reported in the last week, hoping we stay in this lull for a good while.
Elm Beetle Romance
That novel I finished recently was Daniel Mason's North Woods; it's had mixed reviews but I thoroughly enjoyed it. The author happens to be a psychiatrist, and this recent offering from him is an entertaining look at the happenings in a house in rural Massachusetts over several centuries. I had a great chuckle from a brief description of Dutch elm disease complete with a steamy sex scene involving elm bark beetles. Maybe I need to get out more.