respiratory disease transmission – Pediatric Infection Connection

The Wiedermann Thanksgiving Massacree of 199?

Bud WiedermannNovember 24, 2024November 24, 2024Leave a comment

Thanksgiving week has arrived, which for me means making checklists and time schedules and then revising them several times up until Thursday, at which point nothing happens according to schedule and I just go with the flow. It's also a time I remember the infamous Wiedermann Thanksgiving Massacree of 199? (I can't remember the exact year), with apologies to Arlo Guthrie.

Understandably in the past few years, this blog has drifted to the latest public health and epidemiologic trends, but I'm comforted by the fact that respiratory infections remain relatively calm and that this past week's publications allow me to focus more on recent original studies of interest to pediatric healthcare providers and the general public.

Macrolide-resistant Mycoplasma pneumoniae

I'm getting pretty tired of hearing about our resurgence of "walking pneumonia," but this article caught my eye. It's a report from North Dakota, and my interest wasn't in the fact that the investigators found evidence of macrolide resistance; that's nothing new. The bigger question is whether the resistance has major clinical significance. I've stated previously that, because Mycoplasma lower respiratory infection is largely a self-limited disease, it's difficult to know whether antibiotic treatment helps, and if it does, whether the amount of benefit is worth treating with antibiotics. The vast majority of "walking pneumonia" cases in children don't need any nasal swab or radiographic testing, nor any treatment.

The study was small, just based on 10 children of which 8 had macrolide resistance genes detected in their nasal swab assays. Six of them were said to have failed azithromycin treatment, though the authors didn't define treatment failure. Six of the patients who had fever and received doxycycline or levofloxacin became afebrile within 24-48 hours. Needless to say, this doesn't translate to great evidence that macrolide resistance is clinically important; it does point to the fact that we need randomized controlled trials to answer this question. Unfortunately, studies need funding, and this condition isn't likely to be profitable enough for funding from a pharmaceutical company. My only takeaway from the study is that further evaluation and treatment should be considered in children with possible pneumonia in whom symptoms worsen or fever persists more than a few days. Unfortunately, M. pneumoniae susceptibility testing isn't routinely available. For mild community-acquired pneumonia in children, amoxicillin is the treatment of choice, with azithromycin as a second-line agent. Switching to doxycycline or levofloxacin should be reserved for macrolide treatment failure, however that is defined.

Certainly we are having a banner year for mycooplasma respiratory infections, likely a combination of the normal mycoplasma surges we see every few years and lack of exposure during pandemic years. Which brings us to ...

Immune Debt

I really liked this new article that looked at the concept of a dose response effect in immune debt, i.e. that the magnitude of illness we see in rebounds of respiratory infections post-pandemic should be proportional to how much less frequent these infections were during the pandemic. The statistical methods in the study are somewhat beyond my expertise, but I mostly think the authors proved their point that lifting of non-pharmaceutical interventions (NPI) around the world seemed to be a point of increase for various respiratory infections. Here's a sample of the findings.

If this is all true, presumably we'll be back to the "old normal" of seasonal respiratory infections soon (barring another serious pandemic).

UTI Diagnosis

I must confesse my eyes rolled when I saw the title of this new study. Early in my career I was involved in UTI research. I've been very disappointed in analyses of UTI diagnosis in recent years because most of them seemed to ignore how variable accuracy of different UTI diagnostic laboratory methods are, even for something as basic as urinalysis. For example, it makes a big difference whether the number of white blood cells in urine is determined by machine (usually flow cytometry), manual counting by a lab technician with or without use of a hemocytometer, or just a urine leukocyte esterase dipstick. So, I was very pleasantly surprised that this group of investigators highlighted precisely those concerns. This was a study of around 4000 febrile children evaluated for UTI with urinalysis and culture, and the results showed that virtually all urinalysis components were poor at predicting a positive urine culture, defined as > 50,000 cfu/mL of a single pathogen in a catheterized urine specimen. The authors concluded that around 20% of children with febrile UTI could have normal urinalyses but also acknowledged how difficult it is to factor in asymptomatic bacteriuria (estimated rate 2%, but tough to assign an exact number) and specimen contamination. I don't think this study solves any of these issues, but it is an important contribution to our understanding of UTI diagnosis.

WRIS and Nowcasting

Last week CDC published a more detailed explanation of how the time-varying estimated reproductive number (Rt) can be used as an early warning for changes in respiratory pathogen transmission activity. This report is of interest mostly to true epidemiologic nerds, so of course I found it very enlightening. The authors did provide convincing evidence that this methodology has been working well recently.

We're not due for another respiratory illness outlook update from the CDC until mid-December, they only provide these every 2 months, but we remain mostly quiet. I suspect we'll see RSV and influenza hit pretty soon around the country. Again, you can check your own local illness and wastewater activity at the CDC' site.

Beware Studies Based on Administrative Data

This is one of my pet peeves: not the studies themselves, but how too much importance seems to be given to them in the lay press (bolstered by academic organizations seeking to get their names in the news). A new study shows how variable results can be from these databases, using the example of invasive bacterial infections in febrile infants. It's easy to imagine how any system based on diagnosis codes entered into various databases could lead to classification errors, but this report provides an excellent example to keep in mind. Any study using an administrative database should evaluate accuracy of diagnoses on a subset of patients to give some evaluation of the accuracy of their results (IMHO).

New 2025 Vaccination Schedules Published

The information isn't new, just based on prior FDA and ACIP deliberations mostly happening over the summer, but now we have the colorful schedules to use. The AAP has a quick summary of changes.

Happy Thanksgiving!

I have so much to be thankful for this year, and I hope not to repeat the Wiedermann Thanksgiving Massacree of maybe 30 years ago. I won't explain in full; it's too painful to spend anything like the 18 minutes, 34 seconds that Arlo Guthrie took to explain his Alice's Restaurant Thanksgiving Massacree of 1965. (Restaurant namesake Alice Brock died a few days ago.) The short version is that my attempt to create the perfect turkey gravy ended badly in an oil slick of glass shards in the kitchen. Why I'm still allowed to have any Thanksgiving responsibilities at all is a prime example of my wife's incredible powers of forgiveness.

We'll be hosting a relatively small gathering at our place this year. My duties are limited to turkey, gravy, and drinks. Starting today I'll have my checklists made out, separated into daily tasks. Thursday itself will have a well-choreographed timeline to include oven and stove use times in our smallish kitchen. As I said at the start, these scraps of paper will bear little resemblance to how the meal actually unfolds.

I won't go into detail about all the food-borne illnesses linked to turkey dinners, but please make good use of your food thermometer and follow guidelines.

And, speaking of Arlo, some of you might be interested in his live recording of "Amazing Grace" with Pete Seeger in 1993 (around the time of the Wiedermann Massacree!). It's 13 minutes of music and meanderings still meaningful in today's world.

Beautiful Beetles

Bud WiedermannApril 21, 2024April 21, 2024Leave a comment

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.

Tag: respiratory disease transmission