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Where Will the Next Pandemic Come From? Highlights from CDC’s Emerging Infectious Diseases

When monkeypox came from out of nowhere in the spring, it sounded like a joke to our collective COVID-fatigued brains. I think we’ve all got CDC fatigue too. When revised recommendations recently told us it was okay to do or not do what we’ve been doing or not doing for months, I don’t think many people paid attention. I’m glad the agency is finally re-evaluating things.

What may not be as well known is that CDC publishes an excellent, open-access, international, peer-reviewed monthly journal, Emerging Infectious Diseases. Since 1995, EID has provided a window into future health concerns, for us and other animals, with historical and cultural background as well as current epidemiology, covering all sorts of things.

Underlying the research reports on eclectic infectious diseases in the journal are a set of shared and converging factors:
• global climate change shifting habitats
• metagenomics technology comparing genome sequences in environmental samples
• perhaps we’re looking harder
• a much more epidemiologically literate public than pre-pandemic

So I thought I’d investigate the August 2022 issue of EID. The focus is zoonoses – diseases that jump from non-human animals to us.

Nine of the 18 articles are about COVID. Just one is on monkeypox. It recounts patient zero in the US, an “international traveler” who’d been in an African country where the infection is endemic.

Another familiar subject of a lone article is bird flu. Avian influenza viruses that have popped up among poultry in China “showed strong immune-escape capacity and complex genetic reassortment, suggesting further transmission risk.” A few people got bird flu in 2021. So it happens. All we’d need is a version that’s easily transmissible in respiratory droplets for a dangerous new flu to appear.

What other microscopic menaces should we notice?

Four of the papers in the current EID aren’t about people, their inclusion in a zoonoses article collection based on what may be possible: African horse sickness in Thailand, worms in dogs , tuberculosis in red deer, and Schmallenberg virus causing diarrhea and birth defects in cattle, sheep, and goats in Israel.

The other five articles range from the familiar to the unfamiliar, to the exotic, unexpected, and unlikely.

1. Spewing Vomit Spreads Norovirus

For most of us, iwinter vomiting sickness lasts only a day or two. But of the global 685 million cases a year, about 200 million are in children, and about 50,000 die. Norwalk virus spreads through the “fecal-oral route,” but can it do so from vomiting? Swedish researchers found that yes, it can.

They examined infectious virus placed onto bits of human intestine growing in the lab, donated by gastric bypass patients. Theoretically, the small viral load needed to get sick, compared to the abundant virus swimming in vomit, suggested to the researchers that one heaving person might infect more than 150,000 others. The new work supports that estimate. “Norovirus contained in vomit is infectious. Aerosols and droplets from vomiting could be a source of norovirus transmission,” the researchers conclude.

2. Q Fever

The bacteria behind Q fever, Coxiella burnetii, jump to people from milk, urine, feces, and amniotic fluid of goats, sheep, and cattle. Some people have acute fever, chills, fatigue, and muscle pain. A few develop chronic aches and pains without fever and inflammation to indicate ongoing infection. Rarely, Q fever inflames heart valves, a condition called infective endocarditis.

The new paper reports infective endocarditis from Q fever in patients in Israel undergoing transcatheter aortic valve implantation (TAVI), a procedure that snakes a synthetic valve through a blood vessel to the heart. Screening patients for and treating Coxiella burnetii infection before surgery could lower the risk of TAVI.

Q fever was identified in Australia in 1935, then in the US in the early 1940s. “Q” stands for “query,” from when the condition was a mystery – which seems strange since most diseases are mysteries for awhile. CDC began tracking it in 1999. Annual cases usually number fewer than 200. Israel has had overlapping outbreaks over the past 20 years, and the disease is also endemic in southern France.

The researchers thought to screen potential TAVI patients for Q fever after two patients were diagnosed with the infection a few months after the procedure. Perhaps the connection hadn’t been recognized because no one thought to look. The investigators found antibodies against the bacteria in blood samples from 4 of 155 patients who had TAVI.

3. Monkey Malaria

Researchers in Malaysia detected the malaria parasite Plasmodium apparently jumping from monkeys to people in 645 archived blood samples collected from 2011 to 2014 among Indigenous populations from 14 villages in 7 states in Malaysia. They identified six Plasmodium species from two species of macaques. The villages are precariously close to the simian habitats. “Our findings underscore the importance of using molecular tools to identify newly emergent malaria parasites in humans,” they write.

4. Fungi in probiotics

A variant of brewer’s yeast called Saccharomyces cerevisiae boulardii, sold as a probiotic supplement, may seem an unlikely source of an emerging infectious disease, but that’s what was reported in 2005. Its genome differs from that of regular yeast by only 1 percent, but that’s enough, somehow, for the yeast to get into the bloodstream, called fungemia. (Yeast is a single-celled fungus). To add to 59 case reports suggesting a link, a research team from Finland looked at records from 5 major hospitals over a 10-year period and clearly connected the fungemia to the yeast.

The investigators suggest that this particular probiotic not be used for people with certain digestive conditions, and those using catheters, who are immunocompromised, or are critically ill. They point out that not much is known about the benefits of taking the probiotic. But google imaging S. cerevisiae boulardii spits back plenty of bottles festooned with claims – I’ll now be inundated with ads.

5. Anaplasmosis

A man without a spleen, and therefore with poor immunity, encountered tick-borne bacteria of genus Anaplasma in the Amazon rainforest of French Guiana, and then developed fever, headache, chills, and muscle aches. Researchers identified the man from probing the DNA of 363 “clandestine gold miners” along a strip of land between Suriname and Brazil. The gold mining camps are in one of the most biodiverse areas on the planet.

Of eight Anaplasma species known, five infect humans. Molecular typing revealed that the Amazon case was due to a novel version of the pathogen that’s more closely related to bacteria from Brazil.

The newly described bacteria nestle into white blood cells that jumpstart the innate immune response. Further DNA typing traced the novel bacterium to black rats, coatis, and two types of sloths. Previously recognized cases of the infection are from Anaplasma species that jumped into humans from ticks on goats, sheep and cattle, and that land in our red blood cells or platelets. So the blood cell type that houses the pathogen is new.

I suspect in the years to come that more papers are going to be competing for space in Emerging Infectious Diseases, as the living world continues to adjust to a warming planet. Which report will we one day look back on as the first inkling of the next pandemic?

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