Some people report that their antivirus software complains about executables in the bin directory of the SumatraPDF sources.

Is there really a virus in them?

No.

False positives are unfortunately quite common in popular antivirus programs. You can compare your antivirus program’s result with those from other programs by using VirusTotal.

If only one or two report a given file as having a virus, it’s most likely a false positive.