Let us assume, as WHO does, that the virus COVID-19 is not the result of the work done in a laboratory in a state of UN. However, after seeing the consequences of the present pandemia, may be the idea of building a biological weapon may look now more interesting to some persons or groups. The virus of COVID-19 is not, by itself, a classical model for a biological weapon to be used in a war between states. This virus has generated a pandemia, while a biological weapon for war between states should remain in the territory of the enemy. But there are no few other viruses that could become suitable biological weapons. For this and other possibilities (bacteria infection, isolated toxins, etc.) the Biological Weapons Convention entered into force. But it seems that up to the present, no international monitoring institution (as the Safeguards of the IAEA in the field of ionizing radiations) has been established. An international monitoring system could be implemented, for example, by a specialized UN institute, or in another effective frame. This could help to avoid a spread of biological weapons in the (perhaps) more or less near future.