President Trump is in a difficult situation. If he were to disclose circumstantial evidence that the coronavirus virus is a Chinese bioweapon, there would be calls for retaliation against the Communist regime. Such a declaration could lead to more fear, the threat of war, and perhaps a global economic collapse. As it is, the virus is causing a market meltdown. He does not want to contribute to a panic and further collapse.
Politically, his reelection hangs in the balance.