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Published on Leave a comment on The Year in Review

It's fashionable for this time of year to give some reflections on the events of the last 12 months; seemingly every pundit/publication does it in some form or another. I won't buck the trend. What follows is a bit of a "highlight reel," plus the 3 things I'm watching closely for next year.

The Unexplained Explained

Recently we all had the opportunity to watch as a mystery outbreak unfolded in the Democratic Republic of Congo. Was it a novel pathogen set to launch a new pandemic or simply a localized outbreak of a known pathogen, complicated by poor health resources delaying accurate diagnosis and treatment? It took a little longer than I predicted to unravel everything, but we now have an answer from WHO as of December 27. That's still pretty quick, the original alert from the Panzi health zone in the Kwango province was November 29. I'm reassured that our global public health system is working well for outbreak detection.

The case definition used for investigation was fairly broad: "any person living in the Panzi health zone from September 2024 to date, presenting with fever, cough, body weakness, runny nose, with or without one of the following symptoms and signs: chills, headache, difficulty breathing, malnutrition, body aches." Here's an excerpt from the report:

"As of 16 December, laboratory results from a total of 430 samples indicated positive results for malaria, common respiratory viruses (Influenza A (H1N1, pdm09), rhinoviruses, SARS-COV-2, Human coronaviruses, parainfluenza viruses, and Human Adenovirus). While further laboratory tests are ongoing, together these findings suggest that a combination of common and seasonal viral respiratory infections and falciparum malaria, compounded by acute malnutrition led to an increase in severe infections and deaths, disproportionally affecting children under five years of age."

In other words, it was a combination of known pathogens already present in the area, layered on a background of falciparum malaria and malnutrition: a perfect storm. Let's hope the added health resources will dampen the outbreak in this very rural, isolated region of the DRC. Nutritional support is particularly needed.

WHO 2024

The WHO published its look back at 2024, including "highlights, breakthroughs and challenges." Many countries achieved milestones in either elimination or significant decreases of a number of diseases, including human African trypanosomiasis, leprosy, lymphatic filariasis, trachoma, malaria, measles, and mother-to-child transmission of HIV, syphilis, and hepatitis B. Their Expanded Programme on Immunization celebrated its 50th anniversary this year, with an estimated 154 million deaths prevented, most of them infants.

WRIS

CDC took a bit of a holiday break this week, so the level of detail in reports is less. However, Winter Respiratory Infection Season is officially High nationally.

The big 3 (covid, influenza, and RSV) all are increasing at this point. I'm hoping they don't peak at the same time and cause big logjams in healthcare settings.

What I'm Watching For

Mpox

In spite of the few cases in North America, Asia, and Europe, mpox is still primarily an African problem. As we know, however, no communicable disease in one area is just a problem limited to that area - international spread is always a few contacts away. In that regard, I found a recent review/opinion article enlightening.

Of interest, smallpox (vaccinia virus) vaccine protects against mpox infection. Our success in eliminating smallpox and subsequent cessation of smallpox vaccination led to a new population susceptible to mpox infection. A major hurdle to control the outbreaks will be vaccinia virus vaccine testing and distribution to high risk populations.

Avian Influenza

The influenza A H5N1 viruses now circulating in birds (both domestic poultry and wild birds) and dairy cows is the most likely source of a new pandemic, but fortunately the risk is still very remote especially if the public health system can keep on top of tracking infections and characterizing variants.

In the past week we learned that feeding your cat raw pet food derived from poultry is not a good idea, it resulted in 1 cat death in Oregon. I think most of us could have predicted that. One thing for cat owners to keep in mind is that the current avian flu, while still causing some respiratory symptoms in felines, is noteworthy for neurologic symptoms.

Also this week we learned about the mutation found in the hemagluttinin gene segment in the Louisiana human patient with severe avian flu illness. This is the H1 part of the virus which is important for attachment to respiratory epithelial cells. Mutations in this area can increase the effectiveness of spread in humans. However, it is completely expected that a human infected with the virus and experiencing severe disease would develop these types of viral mutations. What would be more concerning is if an isolate from a bird or cow developed such mutations, because of the potential for wider spread.

The risk for widespread human A H5N1 infections is still extremely low. I'll be watching in 2025 for any evidence of human-to-human transmission as well as any significant changes in the virus circulating in the wild animal kingdom. Again, I'm reassured that surveillance is allowing for rapid sequencing of human isolates. I hope that resources continue to be available to track this virus in animal and human populations.

SARS-CoV-2

Covid remains a wild card. It has perhaps the highest mutation rate of any virus causing human disease, it has yet to develop a true seasonality like other coronaviruses making it difficult to plan vaccination recommendations, and infections are still relatively frequent plus underreported due to lack of resources for testing, public apathy, and misinformation/disinformation fueling political decision-making. In short, we're in big trouble if another new variant appears with significantly greater pathogenicity and infectivity.

WHO published another year in review on covid that included a big overview of what's happened since 2020. They do note that our tracking systems worldwide are diminished compared to earlier in the pandemic, so recent data are likely to be significant underestimates. In the post-pandemic phase, we all need to transition from the type of extensive pandemic case tracking into a more sustainable surveillance system similar to what we do for influenza.

I was surprised to see some areas blank for what's going on the US, perhaps due to delayed reporting, and I was also a bit overwhelmed trying to decide what graphs to display here; if you're interested I'd suggest perusing the document itself. First, I've copied a quick highlight summary:

  • While there are periodic waves of COVID-19 in some countries, SARS-CoV-2, the virus that causes COVID-19,
    largely circulates without clear seasonality and continues to infect, cause severe acute disease and post
    COVID-19 condition.
  • The impact of COVID-19 has varied by country depending on the circulating variants, national policies,
    capacities to respond and access to countermeasures.
  • WHO’s ability to monitor circulation, severity, virus evolution and impact is challenged by reduced
    surveillance, testing, sequencing, limited integration into longer term infectious disease prevention and
    control programs, and reporting, as Member States adapt from crisis management to longer term prevention
    and control of COVID-19.
  • Changes to COVID-19 surveillance over the past five years have been consistent and expected, adapting to
    the changing landscape of the pandemic. Many Member States are transitioning from comprehensive case
    reporting to integrating SARS-CoV-2 monitoring into existing respiratory disease and infectious diseases
    surveillance systems. This is an important step towards sustainable infectious disease surveillance,
    monitoring and risk assessment. At the present time, the integration of SARS-CoV-2 into existing influenza
    surveillance systems is variable across regionsranging from 41% in countries from the Western Pacific Region
    to 96% in countries in the European Region.

Here's a great overview of the past few years on a global level.

Even with more inaccuracies in tracking recently, it's nice to see how far we've come in lowering cases and deaths.

Here's a look at deaths by age group, but what isn't apparent in the graph is that mortality rates in infants are comparable to mortality in 20-45-year-olds. Another advertisement for vaccination of pregnant people, who themselves are in high risk group.

And here's the crazy lack of seasonality expressed as percentage of positive tests. I might be tempted to see a trend towards winter seasonality, but remember these data include the southern hemisphere and thus we should see a biphasic pattern if/when seasonality develops.

And lastly a look at how far our variants have drifted over time.

Auld Lang Syne

My apologies to Scotsman Robert Burns, but I must turn to Londoner (with Scottish heritage) Sir Rod Stewart for my favorite version of the song at Stirling Castle in Scotland, complete with bagpipes.

Wishing everyone a Safe and Happy New Year. See you next year.

Published on Leave a comment on All Politics is Local

U.S. Representative Tip O'Neill popularized this phrase in the early 1980s, but perhaps it lost its meaning in later years. Has that changed? Infectious diseases, on the other hand, are most certainly not local.

Infectious Diseases Abroad

Any ripple in communicable infectious diseases in one locale inevitably affects others in far-away locations. Last week saw a number of ripples.

(Not) Measles in American Samoa

Yes, I'm aware that American is a US territory, but it certainly qualifies as far-away.

In 2023, health authorities in American Samoa went on a wild goose chase based on non-recommended testing practices of a suspected case, resulting in a large expenditure of time and money with no benefit. I'm not faulting Samoan practitioners, they had to deal with a lack of available testing resources in the setting of an island rocked by a deadly measles outbreak a few years ago; that outbreak had been fueled in part by prominent anti-vaccination proponents. This recent episode should serve to remind us of proper use of measles diagnostic testing which relies most prominently on use only for individuals who fulfill proper case definitions.

The above report was in last week's MMWR which also contained a WHO measles update. Here's a comparison of 2000 and 2023 measles cases and deaths (note North America is not included in these numbers.)

Severe Avian Influenza in Canada?

Last week Canadian officials confirmed that a critically ill teenager is infected with influenza A H5N1. The source is still unknown, and no close contacts are known to be infected. It's been very tough to get details about the patient's illness, but after going through a transcript of a British Columbia health official's briefing on November 12, it seems that the previously healthy child presented with typical H5N1 symptoms of conjunctivitis, cough, and fever, but then several days later had deterioration. That sequence of events, a sort of biphasic illness, is classic for secondary bacterial complications of influenza. Influenza virus infection of any type can be complicated by secondary bacterial processes, including sepsis and toxic shock syndrome, usually several days after initial flu symptoms begin. Canadian authorities haven't provided any more details, but I wouldn't be surprised if this is what's going on. I'm hoping it was recognized quickly and his healthcare team can return this person to normal health.

Along these lines, NASEM just issued a new publication detailing research priorities for avian influenza A H5N1 readiness. Some of this is already happening, and I hope funding priorities will continue to support planning.

Mpox Update

Last week WHO updated the status of the mpox outbreaks across Africa, a mixture of good news and bad news. Priorities are delivering vaccine to those at risk and implementing newer PCR testing for mpox just approved by the AfricaCDC. Also this past week we learned of the first mpox clade 1 case in the US, occurring in a traveler returning from Africa.

Number Needed to Vaccinate for Covid in the UK

I've mentioned in previous posts that the UK recommends many fewer groups for covid vaccination than we do in the US, primarily because of cost considerations. Last week the UK's Joint Commission on Vaccination and Immunization gave us a bit of a closer look at how those decisions are made with some NNV calculations. NNV (along with its cousin Number Needed to Treat for medication) are a good way to explain "bang for the buck." NNV simply refers to the number of individuals needed to vaccinate to prevent one additional case of the infection, compared to no vaccination. It depends on many variables including the rate of the disease and the number of susceptible individuals in the community and the vaccine effectiveness. Also, NNVs vary with the outcome of interest, such as infection versus hospitalization versus death. It's increasingly harder to calculate NNVs for covid vaccine because of asymptomatic infections and less widespread testing being performed.

The JCVI didn't give us NNVs for all age groups, but they did provide a close look at pregnant people and infants under 3 months of age, the latter group of course not eligible for vaccination and dependent on maternal immunity passed to them transplacentally. I had to dig into attachments to the reports, but here's the bottom line: NNV to prevent hospitalization of a pregnant person is "just under 2000" and "around 300,000" to prevent severe hospitalization. I couldn't find a definition of severe hospitalization but from the context it appears to be something more than overnight observation but less than ICU admission.

For infants < 3 months of age, NNVs (for maternal vaccination) were "under 500" for any hospitalization, "just over 13,000" for severe hospitalization, "almost 190,000" for ICU admission, and ranged from 380,000 to 1.5 million for mortality, the latter extremely hard to calculate due to rarity of the outcome. (But we're all thankful that it is rare.)

Just for comparison, NNV for flu vaccine to prevent 1 additional outpatient visit or 1additional hospitalization in children 6 - 59 months of age ranged from 12 - 42 and about 1000 - 7000, respectively, in one study.

Novavax Combination Covid-Flu Vaccine Study Allowed to Resume

I mention this item mostly to show how well our vaccine safety oversight is working. This study was paused when 1 phase 2 study participant developed what was initially diagnosed as motor neuropathy (with concern for Guillain-Barre syndrome) but then turned out to be amyotrophic lateral sclerosis, not an inflammatory disorder plausibly related to vaccination. This is one of many mechanisms for detecting evaluating rare events after vaccination. Novavax now can proceed with phase 3 studies.

E. coli O157:H7 Outbreak Numbers Grow ...

... but not related to ongoing infection, simply reflecting a delay in case reporting/verification. CDC and FDA report we are now up to 104 cases spread over 14 states. Of the 98 persons with more detailed information available, 34 were hospitalized and 4 developed hemolytic-uremic syndrome. "Of the 81 people interviewed, 80 (99%) report eating at McDonald's. Seventy-five people were able to remember specific menu items they ate at McDonald's. 63 of 75 people (84%) reported a menu item containing fresh slivered onions."

The case map strongly resembles the distribution map for the suspected onions which are now out of the food chain.

In the meantime, we have another E. coli O157:H7 outbreak, this time associated with carrots. [Correction added 11/18/24: this outbreak is due to E. coli O121, not O157:H7 as originally stated.]

I have a feeling I'm going to be washing my salad items more carefully for a while!

WRIS

The winter season still hasn't started, so I'm reduced to browsing the wastewater maps, all updated through November 14 and current through November 9. Here is maybe a look at things to come. First, here's covid:

Now flu (wastewater only tracks influenza A):

Last but not least, RSV:

I'm a Throwback

When I started practicing medicine, implicit in my professional obligations was the duty to do my best to treat anyone who presented to me, without regard to their backgrounds including race, gender, sex, legal status, and, I guess must be said in today's world, political affiliation. Having practiced in Washington, DC for over 40 years, that last category came up frequently as I encountered parents who were elected officials and/or involved in jobs in the political realm. In keeping with that sentiment, I'll still be keeping politics out of this blog and restrict my pontification to infectious diseases. I'll also avoid commenting on various conspiracy theories and other wild ideas emanating from individuals with no scientific basis for their claims. I will, however, comment on any proposed policies related to pediatric infectious diseases where scientific analysis can enlighten the discussion. Nuff said for now.

Published on Leave a comment on A Modest Proposal

Quite an eventful week! In general, I try to keep politics out of my commentary, though I fell short of this goal in my February 25, 2024, post where I blasted the Surgeon General of Florida; that may be the only time I've singled out an individual in a negative manner in this blog. Now, I find that his name is being mentioned as the next Secretary of Health and Human Services. All of this reminded me of an almost 300-year-old pamphlet.

But first a bit of the other health news from last week.

Mayaro Virus

In spite of my voracious appetite for medical knowledge, the list of viruses I've never heard of is lengthy. Now my list is one item shorter due to a new report. Mayaro virus is another of the arthropod-transmitted alphaviruses prevalent in parts of South America, causing a febrile illness with severe arthralgias very similar to its cousin Chikungunya virus. Primates serve as a reservoir with the primary vector the mosquito Haemagogus janthinomys. If like me you are a bit shaky on some elements of South American geography and history, Suriname is a former Dutch colony located just north of Brazil and has territorial disputes (in light green) with neighboring countries.

Measles in Vietnam

Vietnam is introducing earlier measles vaccines to try to stem an epidemic. In this WHO Western Pacific region report, you can see Vietnam is going the wrong way in measles incidence. Like the rest of the world, we all "enjoyed" a pandemic period where many traditional infectious diseases transmitted by respiratory routes showed significant declines due to non-pharmaceutical interventions, only to now reappear in greater numbers. For measles, Vietnam showed an incidence of 7.4/million population in 2020, dropping to 0.3 in 2022 but now back up to 7.1/million in 2024.

Normally Vietnam recommends measles immunization at 9 months of age, but now this is being dropped to 6 months due to an increase in cases in younger age groups. (You'll need Google translate for this link.)

Computerized Radiograph Interpretation for TB?

Although this study was performed only in adults, I thought it was worth mentioning as a possible glimpse of the future. Investigators in Africa and southeast Asia looked at the performance of a computer program to interpret chest radiographs in about 1400 adults with cough > 2 weeks in duration and found the program to have significantly higher sensitivity than a relatively new blood test for host response gene activation in TB as well as superior to CRP. When trying to diagnose TB in resource-poor settings that may not have access to good molecular and other microbiologic methods for TB diagnosis, we need every tool available. I'll be interested to see how newer methods for TB diagnosis evolve.

More on Bird Flu

CDC reported that 7% of 115 dairy workers at farms known to have infected cows showed serologic evidence of influenza A H5N1 infection. Four of the 8 seropositive workers did not recall having any respiratory signs or symptoms since the cows were first noted to be sick. This rate wasn't terribly different from the 60% of those with no illness history in the seronegative group. Given that H5N1 so far seems to be a mild illness in humans, the finding of asymptomatic infection isn't surprising. Clearly we need a lot more data on human illness in these and other settings.

Benefits of Quadrivalent Meningococcal Vaccine

Of our recommended vaccines, meningococcal vaccine probably has the lowest "return on investment." Meningococcal disease is relatively rare but comes with very high morbidity and mortality when it does occur. This modeling study estimated the number of cases of invasive meningococcal disease in 11-23 year-olds prevented by vaccination during the period 2005-2021. One always needs to take modeling studies with a grain of salt because they by necessity make a lot of assumptions. The authors did a good job of trying to look at all possibilities. They concluded that "vaccination averted an estimated 16 (95% CrI, 8-31) deaths among adolescents aged 11 to 15 years and 38 (95% CrI, 19-75) deaths among those aged 16 to 23 years." I guess those are small numbers when compared to the entire US population, but this is still a meaningful benefit.

WRIS

Things are still relatively quiet, though with regional variations.

I did happen to note that wastewater levels of RSV are very high in Maryland, so maybe that will be the first pathogen to increase in my region.

Make America Healthy Again

I feel like the MAHA acronym was one of the nicer-sounding political slogans to appear recently. However, the fact that it was popularized by a notorious pseudo-science fringer concerns me for what might lie behind MAHA. That made me recall a short treatise by Jonathan Swift (of Gulliver's Travels fame) that I came across a long time ago. I read it again a few times this week, and this highly satirical essay entitled "A Modest Proposal" is worth 10 or 15 minutes of your time. I think it is best read without knowing where the narrator is going, so I'll give you a SPOILER ALERT. You can read the original document in the link now, before reading what I write below, or you can just forego the surprise and keep on with my take below.

The narrator beings with an "objective" view of the problem, in 18th century Ireland, of the economic woes of a large section of the populace. He particularly hones in on the difficulties that parents in lower economic strata have in providing for their children. After going through some numbers assumptions that we can only guess at the accuracy, he decides that Ireland has about 120,000 children born to impoverished parents annually. How can the country solve this problem? He offers his modest proposal, or "humble solution:" It's a sudden turn in tone, to say the least.

"I have been assured by a very knowing American of my acquaintance in London, that a young healthy child well nursed, is, at a year old, a most delicious nourishing and wholesome food, whether stewed, roasted, baked, or boiled; and I make no doubt that it will equally serve in a fricasee, or a ragoust."

Yes, Mr. Swift in his satirical essay is proposing cannibalism as a solution to poor families trying to raise their children. He goes on to describe various details of preparation and serving.

MAHA sounds OK now, but I fear of this becoming another modest proposal. I'll withhold my judgment until we see more details of the plan.

Published on Leave a comment on Winding Down (Again)

After one failed retirement attempt, I'm trying again. I just entered a new phase to decrease my coverage of inpatient telemedicine services at regional hospitals and, if demand isn't increasing terribly, I'll phase out completely. In the meantime, I'm revving up for watching the Winter Respiratory Infection Season (WRIS).

WRIS

Nothing strikingly new or concerning on the covid, influenza, and RSV fronts, according to CDC. Respiratory illnesses, wastewater levels, and ED visits are pretty flat or decreasing most places. Florida is starting to show an increase in RSV; typically that region starts sooner than the rest of the country. Of course all viral activity varies geographically, and you can look at your own region with CDC's interactive program at that link.

I admit to having some personal interest in following this closely now. I'm trying to figure out timing of my flu vaccine; as a septuagenerian I may have more rapid waning of immunity after vaccination than do younger generations, plus preliminary data from the Southern Hemisphere suggests a slightly lower flu vaccine effectiveness this year. The key term here is preliminary. These estimates are based on very low sample sizes, and estimates always change once the full season can be evaluated.

Speaking of vaccines, the UK provided a more straightforward guidance for covid vaccination this year. The eligibility groups are pretty limited:

During the 2024 autumn campaign the following groups should be offered a COVID-19 vaccine:

  • all adults aged 65 years and over including individuals aged 64 who will have their 65th birthday before the campaign ends (31st March 2025)
  • residents in a care home for older adults
  • individuals aged 6 months and over who are in a clinical risk group, as defined in tables 3 and 4 of the Green Book chapter 14a

As I've mentioned before, the UK with its National Health Service relies heavily on cost effectiveness analyses, leading to a more restricted target population than in the US.

Two Viruses on the International Scene ...

Marburg Virus in Rwanda

Marburg activity in Rwanda is increasing, and the CDC sent out an advisory last week. Marburg virus is another of the hemorrhagic fever flaviviruses, like Ebola; it has a high fatality rate. As in other hemorrhagic fever virus outbreaks, healthcare workers are at high risk if they are not careful with exposure to blood and body fluids. Most of us remember the spread of Ebola to the US, and already there's been a scare in Hamburg, Germany, but the ill traveler returning from Rwanda tested negative. The name comes from the German city of Marburg which was one of the sites (the others were Frankfurt, Germany, and Belgrade in what is now Serbia) of laboratory outbreaks of the illness in 1967, linked to African green monkeys imported from Uganda. Let's hope efforts to contain the infection are successful, but it's a tough task in low-resource regions.

Perinatal Chikungunya

A new study from Brazil suggests a relatively high rate of transmission of this virus from pregnant people to their newborn infants. The study period covered the years 2016 - 2020. Here's the summary numbers:

Symptoms in infected infants included, in addition to rash and fever, some more severe conditions like DIC, vesiculobullous eruption, seizure and encephalitis, and respiratory failure. It was both a retrospective and prospective case series, and I learned a new term: ambispective!

... But Also Some International Success

The WHO recently declared Brazil has successfully eliminated lymphatic filariasis as a public health problem, a major milestone. The only countries successful previously with filariasis were Malawi and Togo in the WHO African region; Egypt and Yemen in the Eastern Mediterranean region; Bangladesh, Maldives, Sri Lanka, and Thailand in the South-East Asian region; and Cambodia, Cook Islands, Kiribati, Lao People's Democratic Republic, Marshall Islands, Niue, Pilau, Tonga, Vanuatu, Viet Nam, and Wallis and Futuna in the Western Pacific region. Time to dig out that world map!

Filariasis is one of 20 Neglected Tropical Diseases targeted by WHO for improved control by 2030.

Lower Vaccination Rates in US Kindergartners

CDC updated vaccine coverage rates for the 2023-2024 year and, no surprise, it's dropping. The decrease may be driven at least in part by an increase in non-medical exemptions. This news doesn't bode well for future outbreaks of vaccine-preventable diseases, but the clinical impact is largely determined by geographic distributions at the community level. The site has a lot of data, worth some browsing, but here's a quick look at MMR coverage by state for 2023-2024:

Any state that isn't the darkest blue has high risk for outbreaks. Even within the dark blue states any pockets of poor vaccine coverage, such as communities or schools that have high rates of vaccine-averse parents, could see outbreaks.

How's Your Outpatient Antibiotic Prescribing Score?

A cross-sectional database study of about half a million antibiotic subscriptions in 2022 from Tennessee showed some interesting results. The investigators looked at both appropriateness of antibiotic choice and duration of treatment; only 31% of prescriptions were appropriate for both. Here's the quick look at optimal antibiotic choice by disease:

Here's what it looked like for duration of therapy. Standard durations reflect current guidelines, whereas contemporary durations are taken from more recent studies suggesting shorter courses are effective. The number of days in parentheses are the contemporary durations.

Again, another study worthy of browsing if you commonly prescribe antibiotics for these conditions.

November 5 is Fast Approaching

Although I'm trying to wind down my practice, it seems like my to-do list is twice as long now. We're all busy, but please don't forget to vote!

Published on Leave a comment on Invasive Species

Last week I outsmarted myself. The closing photo in the September 8 blog I was sure would result in at least 1 person calling me out; I was then going to follow up in this week's post to explain about invasive species. I guess I forgot to factor in the politeness of my audience in not wanting to berate me for mistakes. (This is a more preferable explanation than the alternative that no one even read that post!)

Still not much going on with our summer respiratory season. The percentage of ED visits due to covid continues to fall nationally.

However, covid wastewater levels in the western US plateaued or even increased a little.

Measles Still Here

It looks like we have settled into a persistent trickle of cases in the US. I'm still holding my breath hoping we can avoid another major outbreak this year. The official tally for 2024 now is 251 cases from 30 states and DC.

Not included in the totals above is a new case occurring in an unvaccinated student at Western Kentucky University, probably acquired during international travel. It looks like that person attended several public events over a few days in late August; with an incubation period of around 2 weeks, we should be hearing soon if secondary cases resulted from this person.

Meanwhile, the UK has reported a measles death in a "young person who was known to have other medical conditions." With 2465 confirmed measles cases so far this year, the UK is much worse off than we are in the US. Still, it's unsettling to hear about measles deaths in high income countries. The UK has had 1-5 deaths per year since 2019 but hasn't had double-digit death figures since 1988. Best estimates are that, even with the best medical care, 1-3/1000 children with measles will die.

A Couple Vaccine Updates

Nothing really new here, but it's easy to overlook important guidance with the flood of emails and other reminders we receive. First is the official statement from ACIP about Hib vaccination for American Indian and Alaskan Native infants. It is the follow up from an ACIP meeting last June. For both socioeconomic and biologic reasons, it's been clear for decades that this population has a very high rate of Hib disease and also a less robust response to most Hib vaccines compared to the general US population. The best Hib vaccine for this group is a conjugate using the Hib polysaccharide PRP joined to an outer membrane protein from Neisseria meningitidis. The OMP is a carrier protein that helps infants form antibody to PRP, the real protective antibody here. This is the basis for all conjugate vaccines; it fools the infant immune system into thinking it is seeing a protein antigen rather than a polysaccharide antigen; PRP and other polysaccharide antigens are not well recognized by infant immune systems - normal infants even fail to form antibody to PRP with natural Hib disease. Conjugate vaccines fool infant immune systems.

At any rate, for a long while we've only had 1 Hib vaccine with the PRP-OMP combo: PedvaxHIB. This summer we saw FDA approval of Vaxelis, a hexavalent vaccine with DTaP, IPV, HepB, and Hib, the latter using the PRP-OMP product. Vaxelis is now officially recommended as an option for the AI/AN infant population, as well as for other infants. The recommendation for the AI/AN group was made on the basis of a phase IV randomized study of Vaxelis versus PedvaxHIB showing good antibody formation in both groups. No effectiveness study was performed because this population didn't have enough Hib disease present at a background rate to determine any significant differences with a new vaccine - PedvaxHIB has worked very well for these children in the past, another vaccine success and cause for celebration.

A second vaccine update is just the recommendation, again from CDC, for the next round of covid vaccines recommended for everyone 6 months of age and older. Again, nothing new, but it's a good resource to have all that information in one document. The tables serve as a quick reference for many different situations.

Mosquito Invasion

Any ID physician worth their salt will obtain an extensive travel history when seeing patients. We are mostly looking for clues to diseases seen mostly in international travelers, such as typhoid fever and the vector-borne infections that include dengue, chikungunya, malaria, and others. However, sometimes the travel history is negative but the patient ends up having one of those exotic diseases, acquired locally in the US (aka autochthonous infection). Such is the case recently with autochthonous dengue fever cases in Los Angeles County, CA. These cases appear when there is an existing reservoir of infected people plus a reservoir of the vector. For dengue virus, the vector is the Aedes mosquito, specifically A. albopictus and A. aegypti, plentiful in much of California.

The range of these mosquitoes have been increasing the past few decades at least, mostly due to warming of our climate. The last extensive study of Aedes presence in the US was in 2017, summarized by CDC.

As one of those people who seem to be particularly tasty for mosquitoes, I find it interesting (and depressing) that we have about 200 different species of mosquitoes in the US. I'm not terribly comforted by the fact that only about a dozen of these can transmit those infections we worry about. Besides the Aedes genus, we also need to worry about Anopheles and Culex mosquitoes.

Of these, it is Aedes that is the most versatile in transmitting disease to humans, implicated in Cache Valley virus disease, chikungunya, dengue, eastern equine encephalitis, La Crosse encephalitis, and zika infections. Anopholes can spread Cache Valley virus, and Culex are implicated in eastern equine encephalitis, St. Louis encephalitis, and Oropouche virus, though midges more commonly spread the Oropouche. Other viruses such as Jamestown Canyon virus can be spread by many different species of mosquitoes and vary with time of year and location.

As our global temperatures have warmed, the mosquito season has lengthened; in many locations mosquitoes are out and about throughout the year. Also, the idea that high altitudes are safer from mosquito-borne infections is becoming invalid in many parts of the world, including the US. It wasn't the altitude per se that mosquitoes didn't like, it was the cool weather which now is warming.

I realize that for many of you this is already too much mosquito information, but if you want more visit Arbonet.

More Invasion

Getting back to last week's post, I had mentioned that my wife was outside working hard to clear our back yard of poison ivy while I was indoors typing leisurely. It turned out she didn't find any poison ivy. The photo I placed at the end of the post wasn't poison ivy but rather a portion of the massive porcelain-berry plant she removed instead. While poison ivy is a native plant, not invasive but still hated, porcelain-berry is a horribly invasive vine deliberately introduced into the US for its attractiveness but quickly discovered to spread indiscriminately, eliminating native vegetation in its path. It is the plant world equivalent of pod people.

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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