The first case of COVID-19 was not confirmed until December 2019. The impact of the Miliatary World Games in October cannot be proven.
According to the New York Times, a Chinese government spokesman, Zhao Lijian, said that American athletes participating in the Wuhan Military World Games may have “brought the epidemic to Wuhan,” in October 2019. There is no evidence to prove this. The New York Times notes that the comments mirror similar accusations made against China on the origins of the pandemic, and have given way to a wave of disinformation and propaganda.
In May 2020, The Times reported that the French athlete Elodie Clouvel had bolstered speculation about the role of the games in the spread of COVID-19, as doctors told her it was likely that she had contracted the virus after attending the event, but this has not been confirmed. There have also been anecdotal reports of athletes claiming they felt unwell after attending the event, but this has not been reported or confirmed by any trusted media outlets.
As it stands, the earliest cases of COVID-19 were not seen until December 2019 in Wuhan, China. Any cases before this are purely speculative.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19, including symptoms, prevention, and available treatment, please refer to the World Health Organization or your national healthcare authority.