Asthma Syndromic Surveillance for EV-D68 & acute flaccid myelitis (AFM)

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Background Information

Acute flaccid myelitis (AFM) is a rare but serious condition that affects the nervous system, causing limb weakness and paralysis, mostly in children. While no definitive cause of AFM has been confirmed, some strains of enterovirus, specifically enterovirus D68 (EV-D68), are believed to be associated with AFM. The most common respiratory symptom of EV-D68 is asthma. While EV-D68 is thought to be a cause of AFM, current surveillance systems do not capture when, where, and to what extent EV-D68 is circulating, so preparing for increases in AFM is challenging.

What was CO Tracking’s role?

Colorado Tracking built, maintains, and operates a syndromic surveillance model that monitors all ED visits with asthma as the primary complaint diagnosis code from Children’s Hospital Colorado (CHCO). Tracking receives data weekly from CHCO's network of care. The model compares weekly asthma visits with a forecast of asthma burden and tests for statistically significant anomalies. 

What product or output came from CO Tracking’s role?

The results of the model and alarm function are shared bi-weekly during enterovirus season with clinical and public health partners via an R Shiny application.

What action or decision was taken to resolve the problem?

The model detected a significant increase in asthma exacerbations beginning the week of 8/14/2022, which correlated with additional surveillance and clinical data from Children’s Hospital CO. The model has not produced an alarm signal during an increase of COVID, RSV, or influenza. It has only alarmed during increased EV D68 circulation. CDPHE also issued a Health Alert Network (HAN) notification on 9/1/2022. 

What was the outcome of this action or decision? 

The model results prompted CHCO to question the results of its PCR surveillance assay, which was not detecting EV-D68 circulation. The information from the asthma surveillance tool led CHCO to expedite the validation of an updated set of PCR primers, which detected a high rate of circulation of the B3 strain of EV-D68. This confirmation then allowed CHCO to activate its preparedness plan, which included increases in staffing schedules, securing the supply chain for asthma medications, and alerting providers to the possibility of cases of AFM. Ongoing asthma surveillance continued to help inform EV-D68 preparedness throughout August and September.

Quantify the impact or the resulting action 

There are numerous articles documenting the event and CHCO's response: Salon articleSee also STAT News article. Colorado issued a local HAN advisory, and CDC issued a related national HAN advisory on 9/12/2022: CDC Health Alert Network.