The latest Windows 7 and Windows 10 April 2019 Windows Update is having issues with some Anti Virus vendors. Microsoft has acknowledged that both versions of Windows may have serious issues if incompatible anti virus software is installed. Microsoft has detailed in their support document for the latest update: https://support.microsoft.com/en-au/help/4493472/windows-7-update-kb4493472 :that it has worked with multiple anti virus software vendors to figure out why their update is causing issues for some users.
McAfee Anti Virus is one of the software that will trigger bugs in Windows 7 and Windows 10. The bug appears to degrade performance significantly and seems to effect Windows 7 upgrades more than Windows 10. There is no known fix for this issue and Microsoft and multiple vendors are currently working on resolutions. Microsoft is saying if you are running one of the problem antivirus platforms that you should not upgraded to Windows Update KB4493472 or if you have you should disable your antivirus (which is not a good idea).
A better idea might be to disable the problematic anti virus and download a temporary free anti virus, like Avira, until Microsoft can resolve their issues with your anti virus of choice.
Latest Update:
If you want more information on antivirus products that are having issues with this latest Microsoft Windows bug, see this article on ghacks: