acute flaccid myelitis – Pediatric Infection Connection

It's been an eventful week for me but relatively quiet in the world of infectious diseases. I've just returned from a week's trek in the semi-wilds of Colorado. You may recall that last week's post included a mention of mosquitoes and high altitudes, noting that climate warming has been accompanied by trends of more mosquitoes at those upper elevation. I'm happy to report that after spending the week in the great outdoors at 5000 - 10,000 feet I only had a few bites and didn't even touch my insect repellent.

Turning skyward, I was able to view the September 17 partial lunar eclipse from Mesa Verde National Park; sadly my antique cell phone camera was unable to capture it. This morning I consulted my trusted 2024 print edition of The Old Farmer's Almanac to remind myself of the difference between an equinox and a solstice. The earth's axis is tilted at 23.5 degrees from the perpendicular as it revolves around the sun, and the equinoxes occur when both northern and southern hemispheres equally face the sun. Northern hemisphere solstices occur when the North Pole is most tilted towards (winter) or away (summer) from the sun. I learned so much this week!

Pertussis

Whooping cough was in the news recently, though really this is just a return to "normal" after the pandemic years. Here's the long view from CDC data.

On a more recent view, you can see the age breakdown.

I was involved in pertussis immunology and vaccine research very briefly in my career. I always like to mention an oldie-but-goodie article from 1992 showing that about one-quarter of UCLA college students with cough lasting longer than 5 days showed evidence of recent pertussis infection. It's a good reminder that pertussis in adults usually looks very different, and milder, than the classical whooping cough in infants. Diagnosis is difficult unless you think about pertussis as a possbility.

Maybe not so coincidentally with these news reports, the FDA VRBPAC meeting last Friday focused on using Controlled Human Infection Models (CHIMs) to try to develop a better pertussis vaccine. Yes, that's right, intentional infection of human volunteers to study various aspects of the disease. We need more information to improve pertussis control, given that our current acellular vaccines are less effective (but also with less side effects) than the predecessor whole cell vaccines. Large scale trials are difficult, expensive, and largely impractical in the present era, so it's time for new approaches. A group at the University of Southhampton in the UK presented some preliminary data from a CHIMs trial and also had a nice graph to put into perspective relative mortalities and contagiousness of pertussis compared to other pathogens:

The study itself was just a challenge study of human volunteers to determine the dose of organisms and the immunologic responses surrounding infection and colonization. It seems likely that these types of studies will be utilized more frequently in the future to improve our understanding of pertussis prevention.

Needless to say, I didn't join this meeting live, I was off the grid in Colorado, but I did skim through the recording and slides today. This wasn't a typical VRBPAC meeting where voting occurred, it was more of a discussion to guide future research.

More Wastewater

Speaking of returning to pre-pandemic levels of infection, I've been watching wastewater trends for enterovirus D68. You may recall that this was an enterovirus strain that figured prominently, but not exclusively, in outbreaks of acute flaccid myelitis that tended to occur in even-numbered years - pretty strange.

As you can see, the pandemic really ended this pattern, and nothing new is going on so far this year. However, wastewater numbers, at least for EV D68, have looked very different.

Will we see a blip upwards in AFM cases this year? I hope not.

More Colorado Learning

My landscape designer wife clued me in to the details of the quaking aspens, so named due to the fluttering of the leaves that have their own distinct sound. They are beautiful, both my wife and I wished we had better pictures to show you.

On another note, although I love to learn, one new factoid I happened upon was perhaps less exciting. Hiking at these altitudes, I learned that I'm not as young as I used to be!

If past experience with wastewater monitoring is worth anything, we will see a surge in covid illnesses starting in the next few weeks. And, that may not be the only summer surge in the works.

Wastewater

CDC wastewater data for SARS-CoV-2 is very reminiscent of the last 2 summers when we saw subsequent upticks in covid illness.

Of course this can vary across the country and is less informative due to absence of wastewater tracking in large swatches of the country. Still, you can see that higher levels of activity (the darker the blue the more the virus concentrations, with gray denoting insufficient data) are common all over. (Data as of July 18, 2024.)

Contrast this with the latest map of influenza-like illness that should pick up covid cases - nothing much doing here.

Wastewater tracking methodology is the least changed post-pandemic, so it is the most useful information to use to compare with past years. Monitoring of infections, illnesses, hospitalizations, and deaths have all changed dramatically, due both to changes in individual behaviors in testing use and changes in reporting mandates for communities and medical institutions, with resulting under-reporting of clinical events due to covid. Keep an eye on what happens on the west coast, probably the first region to ring in the clinical surge.

Take-away point: it might be time for high-risk individuals to go back to masking and avoidance of high-density indoor crowds for a while. New covid vaccines may be available as early as next month.

Speaking of Influenza

Not surprisingly, more human cases of influenza A H5N1 have cropped up in Colorado, this time in poultry workers involved in culling infected chickens. Clinical illness is mild. CDC has sent an outbreak investigation team to these sites and, coupled with a serologic survey getting going in Michigan, should help define modes of transmission and range of clinical illness.

PEP Didn't Work for Covid

A new article in NEJM failed to show any benefit of nirmatrelvir-ritonavir (Paxlovid) compared to placebo in postexposure prophylaxis for household contacts of persons with covid infection.

It's a well-constructed study and should end talk about using this agent for post-exposure prophylaxis in most circumstances.

Fear of Flying

No, not the Erica Jong book. I came across a systematic review published recently suggesting that masking was beneficial on long airline flights. It covered studies performed in the early pandemic period so it may not be entirely reflective of current events, but it was interesting.

It's not overwhelming evidence, but wearing a mask on long airline flights might be a choice, both for high-risk individuals as well as for those who just don't want their expensive vacations spoiled.

Enterovirus Surge?

July through October usually is peak enterovirus season in the US, with much variability depending on climate and who knows what else. You may not be aware, but CDC has a National Enterovirus Surveillance System (NESS) set up to monitor enteroviral activity. It is a laboratory based system, and reporting is passive and voluntary, so it tends to have relatively little data and a significant lag in reporting spikes in enterovirus illness. 2023 data, as of April 2024, reported on 193 specimens tested at CDC for that entire year. It is mostly useful for identifying strains responsible for more severe illnesses such as acute flaccid myelitis.

Anecdotally though, it seems as if we're having one of those bumper years for enteroviral disease. In my telemedicine practice at a few regional hospitals surrounding Washington, DC, I've had a handful of newborns with mostly mild illness test positive. Similarly, I'm hearing a lot about hand, foot, and mouth disease from primary care doctors consulting me as part of some nationwide volunteer curbside consults I perform.

If this is true, primary care offices, urgent care settings, and emergency departments could get a little busy with covid and enterovirus illnesses soon.

Tag: acute flaccid myelitis

Happy Autumnal Equinox 2