Two common respiratory pathogens to watch in the months ahead

EV-D68 and Mycoplasma pneumoniae in focus

Today, I want to share some thoughts about public health events that may happen. I have updates on two common pathogens that circulate regularly. I have reason to suspect there may be more-than-usual activity in the near future.

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EV-D68

EV-D68 is a common virus that primarily spreads through respiratory droplets like those produced during coughs or sneezes, and through contact with contaminated surfaces. For most people, the symptoms are mild or cold-like, including runny nose, cough, and fever.

However EV-D68 has been linked to rare but serious neurological complications like Acute Flaccid Myelitis (AFM), which can cause polio-like muscle weakness. Most cases of AFM occur in elementary age children.

Wastewater data from WastewaterSCAN shows an increase in EV-D68 activity across all four regions of the country. Since wastewater data is the only indicator available for this specific virus at the moment, the strength of this evidence is limited. Although I prefer to have multiple data sources, this increase is worth monitoring to see whether AFM cases follow.

Source: WastewaterSCAN

AFM diagnoses spiked in 2014, 2016, and 2018, suggesting a possible every-two-year pattern. However, pandemic control measures interrupted transmission of many common viruses, including EV-D68, and so very few AFM cases were recorded in 2020 and 2022. Now the spike in wastewater makes me wonder whether this year will mark a return of AFM.

Source: CDC

It's worth noting that we haven't seen a spike in AFM cases yet according to CDC data, but the most recent data only goes up to August 1st. The increase in wastewater detection is more recent. September has historically been a common month for AFM spikes, so the timing fits the pattern we've seen in previous years.

There's a lot that is unknown about the condition, so it's entirely possible nothing will come of this clue from wastewater surveillance, but it’s something to be aware of.

For more information about what is and is not known about the link between EV-D68 and AFM, this is a useful paper.

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M. pneumoniae

One of the other pathogens on my radar for the months ahead is Mycoplasma pneumoniae, a bacterial infection that is yet another cause of respiratory symptoms.

M. pneumoniae can lead to a range of illnesses, from mild sore throats to conditions like bronchitis and "walking pneumonia"—so named because the symptoms are often mild enough for people to continue their usual activities.

Although the infection typically affects older children and young adults, the CDC has noted an increase in infections among younger children this year.

Several clinicians have written to me to share that they have seen an increase in cases in their practice this year. Their observations are supported by a recent mathematical modeling study by Sang Woo Park and colleagues predicting a surge in activity in the coming months. The preprint study suggests there will be a wave peaking in the second half of 2024. The authors “estimated peak positivity will be 7.5% (95% CI: 5.6–9.3%), which is 2–3 times larger than the observed peak positivity of 2.8% at the end of 2015.”

Even if the specifics from this modeling study don’t pan out, other researchers have also identified an increase in activity this year, so I think the general expectation of an increase in activity is reasonable.

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Stay well! I’ll be back in your inbox on Monday with the usual Outbreak Outlook.