Viruses are programs that are produced to prevent proper functioning of Computers. They don't usually help in increasing productivity or speed of a Computer while the reverse effects are quite common.
Computer viruses perform unexpected tasks like automatically starting a program again and again and this is their main identification.
A virus can surely have effects on an Antivirus program if the program is not updated periodically. The commonly visible effects include the warnings like file corrupted shown during installing an antivirus. Some viruses automatically uninstall antivirus programs. While others can prevent installing of a new one.
Sometimes the older versions of antivirus programs don't even detect the viruses, this is also one of the effects.
Hence, If your antivirus states No Virus Found then also you shouldn't think that your System is secure.
The best cure is to update you antivirus regularly so that the viruses can be traced and acted upon effectively.