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Published on Leave a comment on The Wiedermann Thanksgiving Massacree of 199?

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.

Published on Leave a comment on The Future is Bright

2023 wasn't exactly the best of years, but at least we didn't slip back into pandemic circumstances. I fear we will see some "old" infections become new again in 2024. General immunization rates are falling; even before that, we saw plenty of pertussis and even some tetanus, but now we may become reacquainted with measles and varicella, among other vaccine-preventable diseases. Time for some of those younger pediatric healthcare providers who have never seen children with these infections to hit the textbooks again - how's that for a New Year's resolution!

Still, we have lots of reasons to hope for improvements in 2024. Maybe AI won't take over the world but instead will help us practice more effectively.

Short Course Therapy for Febrile UTI in Children

The literature just got a bit muddier with regard to treatment duration for pediatric UTI with a new study from Italy. Investigators in 8 pediatric emergency departments randomized 142 children ages 3 months to 5 years with fever and UTI to receive either 5 or 10 days of oral amoxicillin/clavulanate. The study wasn't blinded, and the randomization occurred on day 4 of therapy when urine culture results were available. UTI was defined as a single organism growing at >100,000 cfu/ml in clean catch urine or > 10,000 cfu/ml in catheterized urine, and subjects were followed for 30 days after completion of antibiotic. After a planned interim analysis the study was stopped early due to finding of noninferiority of the short course therapy.

As you can see, the short course group had numerically lower rates of UTI recurrences during this time period. However, this study's results contradict another study, with a somewhat more reliable study design and definitions, that showed short course therapy to be inferior. I reviewed this earlier study in my July 2, 2023 post. The editorial accompanying the new study is an excellent discussion of weighing the relative merits of the 2 studies. Suffice to say, the jury is still out, and I would stick with 10 days of therapy for febrile UTI in most children.

More Evidence for Using Nirsevimab to Ameliorate Bad Outcomes from RSV

Investigators in 3 European countries conducted a randomized trial of the long-acting monoclonal antibody nirsevimab showing benefits in preventing RSV-associated hospitalization, especially in younger infants. Note that subjects for this study were not eligible for receiving nirsevimab currently in these countries; they were all healthy infants less than 12 months of age, born at > 29 weeks gestation, who were entering their first RSV season.

This was a pragmatic trial, meaning that it was carried out under more "real-world" practice situations rather than within the strict confines of "explanatory" trials used with most therapeutic research studies. It lends more evidence to benefits of nirsevimab for young children.

WRIS (Winter Respiratory Illness Season)

Most pediatric healthcare providers across the country know that we are in the midst of a busy WRIS. This also is a time when data are least reliable due to the extended holiday season - reporting lags a bit, so trends seen now are more likely to be revised in the next few weeks. Still, it's worth a look.

Researchers in Stockholm, Sweden, looked at pediatric hospitalization rates for the 3 "tripledemic" viruses during the period 8/1/21 to 9/15/22 and found that rates were higher for RSV than for omicron covid (the time period was entirely omicron in Sweden) or influenza; note especially the numbers for younger children. I'll be interested to see if this pattern is seen in the US this winter.

CDC has a new (to me) section charting epidemic growth status for covid and influenza, i.e. it depicts, by locale, the growth rates but not the absolute numbers of these pathogens. Another interesting tidbit.

Along the same lines is a monthly crystal ball page from CDC, a bit of sticking their necks out to predict what's in our future for respiratory illnesses. The last report is from November 29:

Lots of uncertainties here, but I appreciate the attempt.

Now for a look at our usual sources for data.

FLUVIEW

Circulating strains are still well-matched to this year's vaccine.

Covid wastewater is increasing, and several healthcare facilities across the country have reinstituted masking and other mitigation practices due to high rates in their communities.

RSV is the one "tripledemic" component that seems to be decreasing in most areas.

So, WRIS this year seems to be a double-whammy rather than a tripledemic, still more than enough to strain healthcare resources. I can only dream how much better people's health would be with widespread vaccine acceptance.

We're Still Safe from the AI Bots

I tried to use an AI program, Microsoft Copilot's Suno, to compose a song about this blog. Specifically, I asked it to create a song about the Pediatric Infection Connection blog using the blues genre. Here's what I got.

Their link doesn't exist, nor is there a pediatric infectious disease specialist Dr. Sarah Jones certified by the American Board of Pediatrics. I did find a Sarah Jones infectious diseases pharmacist at Boston Children's Hospital, but she doesn't appear to have a blog and I don't know if she has children.

I think, for the next year, we'll still be able to keep AI from fooling all of us.

Have a Happy and Safe New Year!

Published on Leave a comment on Lots of Thanks This Year

I didn't have any trouble thinking of things to be thankful for this Thanksgiving-time. That might seem odd given the horrific events on the world stage now, and I don't mean to minimize that, but gratitude can coexist with dismay.

First, let's get caught up on this week's ID happenings.

Disappointing Measles News

Measles is probably the most easily transmissible human infection known; a high level (probably 95%) of population immunity is needed to prevent outbreaks. Not surprisingly, a breakdown in immunization rates during the COVID-19 pandemic likely is to blame for increases in measles cases worldwide, as reported last week by the CDC. Concomitant with a decrease in measles-containing vaccine coverage from 86 to 81%, measles cases increased 18% (7.8 million to 9.2 million) worldwide from 2021 to 2022; deaths increased from 96,000 to 136,200. Still, and here's the thankful part, vaccination likely prevented 57 million measles deaths from 2000 to 2022. Here's hoping we can get our global immunization campaigns back on track.

2024 CDC Recommended Immunization Schedules Are Available

Even earlier than advertised, CDC has posted the 2024 immunization schedules. Primary care providers should study these closely due to some complex changes, particularly for pneumococcal and meningococcal vaccines. The AAP has posted a summary of key changes (click on the PDF link). As an aside, I'm a bit irked by what CDC and others call "shared clinical decision-making." Here's CDC's tool for SCDM for meningococcal group B vaccine:

I'm not a primary care provider, but I don't see a lot of help for busy frontline practitioners here. What we really need are more details about choices parents and patients need to consider. Specifically, what are the risks of not getting the vaccine versus those being vaccinated? As stated in the table, meningococcal B infections are relatively rare in the US, so vaccination isn't going to prevent much disease or mortality even with a highly fatal infection. The risks are different depending on individual circumstances. Are frontline providers supposed to have these numbers at their fingertips? Maybe the CDC or AAP will provide them. (Or, if not, maybe I will!)

MIS-C Cardiac Follow-Up

Multisystem inflammatory syndrome in children (MIS-C) following covid infection is very uncommon currently, but we shouldn't forget about monitoring children as they recover from MIS-C. A group at Children's Hospital of Los Angeles reported that even children who did not have clinical cardiac involvement during their acute illness still had some evidence of cardiac injury at the 6-month followup period. Most of the report deals with laboratory, imaging, and other testing, but of the 69 patients evaluated at 8 weeks 15 had clinical symptoms such as chest pain, palpitations, exertional dyspnea, or fatigue. The rate of clinical symptoms was actually lower in the group with no initial myocardial injury, although the difference was not statistically significant. The bottom line: make sure all MIS-C patients have good cardiology followup.

Variations in Influenza Antiviral Use

A group from Vanderbilt reported wide variation in prescribing practice for influenza antivirals during the period 2010-2019 (so, not affected by the pandemic). It is an administrative database study, a study design type that has inherent inaccuracies due to how administrative data is collected. In general, however, a wide variation in practice is an indication that something isn't right. Guideline-concordant compliance was low, for example <40% in children less than 2 years of age, a high risk group. I would have liked to have seen how flu vaccine status affected antiviral use since vaccination greatly lowers risk for severe adverse outcomes, but apparently the database did not contain that information. This is another opportunity for shared clinical decision making with parents; what are the specific rates for infection, hospitalization, etc versus medication side effects (primarily vomiting with oseltamivir) for an individual child, based on their risk factors? That's what a frontline health provider needs when discussing whether to treat a child for influenza.

The "New Normal"

I mention this catchphrase only to bury it. Not only does it seem nonsensical to me, it also is beyond retirement age. Some might wish to apply this catchphrase to the upcoming winter season. I'm strangely thankful/hopeful for this because it now appears we may get to see what a typical respiratory virus season looks like in the post-pandemic era. We haven't seen any weird covid upticks early on, and RSV looks more typical so far without the very severe season we saw last year. Flu may be starting to increase, similar to pre-pandemic seasons. Of course, all of the respiratory virus seasons vary somewhat from year to year. Will covid settle into just another winter respiratory virus?

FLUVIEW is back in business, and the map is heating up especially in the South.

Remember that this is a map of "influenza-like illness" so can capture other respiratory viruses. However, covid wastewater tracking hasn't had much of an uptick.

RSV-NET continues to show increase primarily in younger children, not matching last year's peak but possibly similar to prepandemic waves.

Happy Thanksgiving

I was looking around for something uplifting and fun to mention and happened on "Thanksgiving" by Edgar Albert Guest. Here's an excerpt:

"Greetings fly fast as we crowd through the door

And under the old roof we gather once more

Just as we did when the youngsters were small;

Mother’s a little bit grayer, that’s all.

Father’s a little bit older, but still

Ready to romp an’ to laugh with a will.

Here we are back at the table again

Tellin’ our stories as women an’ men."

I had never read anything by Guest, but I was sold on him when I read his Wikipedia page. Anyone who merits mention by Edith Bunker from "All in the Family," Lemony Snicket, Mad Magazine, and Benny Hill is my kind of guy. Furthermore, Dorothy Parker of Algonquin Round Table fame had the best line: "I'd rather flunk my Wassermann test than read a poem by Edgar Guest." I think maybe she wasn't a fan, but at least she knows her 1950s syphilis testing.

Wishing everyone a Safe and Happy Thanksgiving.

Published on Leave a comment on Happy St. Martin’s Day

I was thumbing through my Farmer's Almanac this morning and noticed a mention of "Indian summer" for November 12. That's not a great term to use nowadays, so I'm opting for the European version called St. Martin's summer or day. I never bothered to see what these terms really meant, but I've learned it represents a period officially from November 11 to November 20 where we experience unseasonably warm weather. We've certainly had that recently, though November 11 and 12 in Maryland is back to cool fall weather.

Miscellaneous Vaccine News

I have no idea what a "miscellaneous" vaccine is, I was just desperate for something to title this section.

A new vaccine to prevent chikungunya virus infection was approved by the FDA this week for individuals 18 years and older at increased risk for infection with this mosquito-borne pathogen. It is a live virus vaccine. As with most arboviral illnesses these days, the vector range is expanding as our climate warms, and transmission has occurred within the US. Still, most infections in US residents are acquired via travel to more endemic areas such as Africa, southeast Asia, and Central and South America. The clinical illness is similar to dengue fever and mostly is a miserable but self-limited illness. However, elderly are at risk for complications, principally chronic joint disease. Newborns also are at risk for more severe disease, including death, and it is unknown whether the vaccine virus could be transmitted to the fetus. The package insert includes precautions for use in pregnant people. The main study supporting approval appeared a few months ago and looked primarily at side effects and antibody response, not actual vaccine efficacy. One big caveat, the manufacturer is required to conduct post-marketing studies to ensure that vaccine recipients do not develop a worse form of chikungunya after becoming infected; this is a possibility though not highly likely. For now, I'd consider this mostly as an option for older individuals at very high risk for infection. Most other US residents should wait for further information about the vaccine, but it's good we have this option available.

This past week also saw publication of new data from Singapore about benefits to newborns of covid vaccination of mothers during pregnancy. It was a cohort study, which is a study design slightly more prone to inaccuracies than are randomized controlled trials, but it did show about 40% efficacy in preventing infection in newborns when their mothers were vaccinated during pregnancy. Of interest, pre-pregnancy vaccination of mothers was not effective in preventing newborn infection. The study covered the period from January, 2022, through March 2023. This is yet another reason to encourage covid vaccination for pregnant people, along with pertussis and RSV vaccination. The benefits do extend to their children.

Unfortunately, we also have some disappointing vaccine news in the category of missed opportunities. First, 2 studies from the CDC demonstrated poor influenza vaccine uptake by healthcare providers. In the first report, flu vaccination rates for HCP in acute care hospitals fell from 88.6 - 90.7% in the years 2017-2020 down to 85.9% in 2020-2021 and 81.1% in 2021-2022. We all know that the pandemic made it difficult to access regular health care for many people, but these are workers in acute care hospitals who didn't have that excuse. The second study looked at a broader range of HCP during the 2022-2023 flu season and showed 81.0% flu vaccination rates in acute care hospital employees and a shocking (to me) 47.1% rate for nursing home employees. Up to date covid vaccination status rates were even more depressing: 17.2% and 22.8% in acute care hospitals and nursing homes, respectively. I can understand why some people may choose not to receive these vaccines, but HCP do have a responsibility to protect those for whom they provide care. (IMHO; I'll get off my soap box now.)

Also in the Debbie Downer category, CDC reported that vaccine exemptions for kindergarteners increased for the 2022-2023 school year. The rogues' gallery includes 10 states (Alaska, Arizona, Hawaii, Idaho, Michigan, Nevada, North Dakota, Oregon, Utah, and Wisconsin) having exemption rates above 5%. Idaho easily came out on "top" with a 12.1% exemption rate. The reasons for high exemption rates are complex, note that the list of states doesn't necessarily follow political lines. States that make it more difficult for parents to apply for non-medical, aka philosophical, exemptions have lower exemption rates overall. An oldie but goodie study also stressed that exemption rates vary within a state, and small hot spots with high exemption rates can fuel outbreaks of vaccine-preventable diseases.

Missed Opportunities to Prevent Congenital Syphilis

The CDC was very busy this past week! Another report looked at missed opportunities for prevention of congenital syphilis in 2022. Looking at the 3761 cases of congenital syphilis reported that year, almost 90% of birth parents received inadequate management. This included no or nontimely testing (36.8% of parents) and no or nondocumented (11.2%) or inadequate (39.7%) treatment. I'm hoping our public health infrastructure can be shored up to lower cases of congenital syphilis, now at a 30-year high.

Tripledemic Update

Rather than showing yet another RSV-NET graph, where data are somewhat delayed anyway, I thought I'd mention a bit more about that system. It is set up in 14 states covering about 8% of the US population. Here's what the distribution and data collection looks like:

I'm not sure why (Veteran's Day?) but FLUVIEW did not update this past week, so nothing new to report there. Wastewater covid levels reported by Biobot remain lowish.

No Hasty Pudding Again This Year

I'm starting to help plan a Thanksgiving menu for later this month, and I was reminded of another ill-named item, Indian pudding. It is similar to the British hasty pudding that uses wheat flour rather than cornmeal. I have a wonderful recipe, dated 1958, from the Durgin-Park Restaurant in Boston. Durgin-Park opened in 1742 and closed in 2019, and this dessert was an icon on their menu. The reasons I won't be having it again this year are multiple but include the fact that I'm the only one in my family who likes it and that it contains about 5000 calories per tablespoon (only slight exaggeration). I think I'll just change the name to Durgin-Park pudding for future reference.

Published on Leave a comment on Yellow Jack in the US? Are You Kidding Me?

It's nice to be back after my brief website repair hiatus. Please let me know if you have any problems or have any suggestions for the website. I'll continue to work on design issues.

I won't attempt to cover all the issues in pediatric infectious diseases appearing during the hiatus. Needless to say, at lot happened, mostly old news by now. Some newer things I won't mention because they appear only in abstract form at national meetings, such as this month's ID Week (Infectious Diseases Society of America and other ID groups) and the American Society for Tropical Medicine and Hygiene. I have seen dramatic changes from the time data are presented at a meeting, which can be preliminary and incomplete, to the final publication or lack thereof. I've become averse to propagating that type of information source.

Yellow jack is another name for yellow fever; it takes its name from the yellow nautical flag that alerted others that yellow fever was on board. A variation of this flag is still used today to alert other ships about health issues on board. You might want to brush up on your yellow fever knowledge now, keep reading if you're intrigued.

Nirsevimab Supply Chain Flop

This isn't news to any practicing primary pediatric healthcare provider. The supply of the newly-approved long-acting monoclonal antibody preparation to prevent RSV infection for all infants has hit a major snag: demand has far outstripped supply. Maybe we will eventually hear the true story of what happened, but basically we are dealing with a single manufacturer who couldn't produce enough product. Even some hospitals aren't able to get a supply to administer to newborns at the time of discharge.

The AAP has a nice RSV page that healthcare providers may find useful, as well as an October 17 webinar with practical strategies. Remember that maternal RSV vaccination at 32-36 weeks gestation is another option to encourage; talk to preganant people visiting your practices. Palivizumab (Synagis) is still available for high risk infants.

Tripledemic Update

We're certainly not anywhere close to a tripledemic at present. Only RSV seems to be on a significant upswing:

Flu season hasn't yet started for most of the country. COVID-19 disease is much more difficult to track now that our tracking methods have changed so dramatically from the pandemic area. I look to wastewater reports as the most consistent indicator over time, and they suggest that we did not have a big spike this fall.

Future Pandemic Preparedness

The Journal of Infectious Diseases finally got around to publishing a supplement on vaccine and monoclonal antibody development for potential future viral pandemic pathogens. It was put together from presentations at a meeting in 2021. Here's a quick overview of the types of pathogens considered:

Comparison of pandemic potential and countermeasures for viral families known to infect humans. Viral families were categorized as having either low/moderate or high pandemic potential and low/moderate or high levels of existing resources and countermeasures. Cross-comparison revealed 10 viral families with high pandemic potential and low/moderate existing resources or countermeasures upon which the National Institute of Allergy and Infectious Diseases will focus its pandemic preparedness activities. Asterisks denote existing vaccine solutions for some viruses in that family; boldface type, potential vaccine solutions for the entire virus family; shaded box, viral families chosen for prototype pathogen selection.

I'm sure many of these names except for Coronaviridae are unrecognizable to most physicians, and several at best are vague even for infectious diseases specialists. Orthomyxoviridae include influenza viruses. Let's hope research funding comes through for the entities in that lower right box.

Yellow Fever

You probably haven't thought much about yellow fever unless you've considered travel to an endemic area, either for yourself or for patients in your practice. We have an effective vaccine available, but it is a live virus vaccine. Risks for vaccine side effects increase with age greater than 60; I actually received yellow fever vaccine for travel when I was in this high risk group; more on that later.

A recent Perspective essay in this week's New England Journal of Medicine raised the possibility of yellow fever reappearing in the US, particularly in the southeastern United States. This is already a problem with other mosquito-borne infections like dengue, chikungunya, and Zika viruses. (Note these are in the family Flaviviridae, also included in the gray box above.) The vectors for yellow fever, Aedes aegypti and A. albopictus, are well represented in the US, and their range is increasing as our climate warms.

Yellow fever is endemic in some parts of South America and Africa, and its range appears to be spreading in recent years. (The maps below are a few years old, updated WHO country recommendations usually are published in November.)

Diagnosing yellow fever without a travel history will be very difficult in most instances. In about 85% of those infected, the clinical presentation is a self-limited, nonspecific febrile illness with chills, myalgia, headache, and some GI symptoms lasting about 3 days. An unlucky 15% have a more biphasic presentation with the second stage appearing after around 48 hours of improvement and characterized by more severe symptoms including jaundice, renal failure, coagulopathy, and other life-threatening problems. At that stage the diagnosis might occur to an astute provider and diagnostic testing can be obtained. No specific antiviral therapy is available.

Yellow fever vaccine is highly effective, and a single dose confers life-long immunity. It is relatively safe, but there are rare severe side effects. These severe reactions are 3- to 4-fold higher in vaccine recipients over 60 years of age:

Yellow fever vaccine associated neurologic disease (YEL-AND; mostly encephalitis, Guillain-Barre syndrome):

  • over 60 years of age = 2.2 cases per 100,000 doses of vaccine administered
  • less than 60 years of age = 0.8 cases per 100,000 doses of vaccine administered

Yellow fever vaccine associated viscerotropic disease (YEL-AVD; similar to severe infection itself with approximately 50% mortality):

  • over 60 years of age = 1.2 cases per 100,000 doses of vaccine administered
  • less than 60 years of age = 0.3 cases per 100,000 doses of vaccine administered

I was over 60 years of age when my travel to Ethiopia caused me to consider yellow fever vaccine. My reasoning wasn't based on the 3- to 4- fold increase in risk, which is a relative risk increase, but rather focused on the absolute risk. This is a topic I've revisited many times in this blog; it has immediately applicability to vaccination of any type but especially for COVID-19 and RSV now.

Adding together the risks for YEL-AND and YEL-AVD for the older population comes to 3.4 cases per 100,000 vaccinations, or 0.0034%. As a comparison, risk of airplane crash is about 1 in 11 million (o.oooo1%) and risk of being struck by lightening is 1 in a million or less (0.0001%). Of course these risks vary by how many miles you spend on airplanes and how often you are out walking around in thunderstorms. Weighing my yellow fever vaccine risks and benefits, I chose to receive the vaccine rather than not travel to Ethiopia where my specific yellow fever risk was very low because I was staying at high altitude for most of the time.

Speaking of Travel

I timed my blog hiatus with a major trip to the Umbria region of Italy. It was a hiking vacation through rural areas with occasional forays into medieval towns and was a wonderful experience. I'm still nursing a few minor musculoskeletal aches and pains - my muscles and joints aren't what they used to be.

In addition to beautiful churches, ruins, and the medieval towns, I was also surprised to see many unfamiliar butterfly species including this Hipparchia hermione example.

Unless otherwise indicated, the content and opinions expressed on this web site are those of the author(s). They are not endorsed by and do not necessarily reflect the views of the George Washington University.
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