No, you misunderstand the terminology. "Subsequent encounter" means with the doctor not with the rattlesnake. AKA followup care during or after recovery.
You can reference ICD codes with the schema.org/code property of schema.org/MedicalEntity and subclasses. https://schema.org/docs/meddocs.html
"Subsequent encounter" is poorly defined. IMHO, there should be a code for this.
"Poorly defined" is poorly defined. Explanations of when to use the D make perfect sense to me.
"The 7th character for “subsequent encounter” is to be used for all encounters after the patient has received active treatment of the condition and is receiving routine care for the condition during the healing or recovery phase. Examples of subsequent encounters include cast change or removal, x-ray to check healing status of a fracture, removal of external or internal fixation device, medication adjustments, and other aftercare and follow-up visits following active treatment of the injury or condition. Encounters for rehabilitation, such as physical and occupational therapy, are another example of the use of the “subsequent encounter” 7th character. For aftercare following an injury, the acute injury code should be assigned with the 7th character for subsequent encounter."