Following confirmation of the outbreak, the American Horse Council and the American Association of Equine Practitioners asked the USDA to co-ordinate data collection, dissemination, and communication efforts among state and federal veterinarians.
The organisations said it was necessary to protect the health of horses and minimise the economic implications of further EHV-1 transmission within states not yet affected.
The American Horse Council said the full scope of the outbreak and a complete accounting for the number of horses affected and/or exposed has yet to be determined.
It expects the federal agency to report on the exact number of horses confirmed EHV-1 positive in the coming days.
The USDA anticipates updating and releasing future incident reports on a weekly basis going forward.
If the current incident results in widespread exposure or a large influx of positive horses, it is likely the information will be released as it becomes available.
"There have been numerous articles citing a wide variation in the number of confirmed cases of the EHV-1 neurological disease in horses," the horse council said.
"This large disparity in epidemiological information underscores the importance of allowing USDA and state veterinarians to collect the appropriate data, verify the information gathered, and disseminate factually correct information.
"Until state and federal animal health officials are able to gather, verify, and disseminate accurate information on the scope of the current incident, it is critical individual horse owners and organisations undertake appropriate and responsible actions to mitigate the welfare and economic implications of potential future transmissions."