Infective vs. Infestive

Able to cause infection; infectious

(epidemiology) A person who is capable of spreading a disease by infecting others.

Infectious.

Example: ‘True love . . . hath an infective power.’;

able to cause disease;

Example: ‘infective agents’; ‘pathogenic bacteria’;

caused by infection or capable of causing infection;

Example: ‘viruses and other infective agents’; ‘a carrier remains infective without himself showing signs of the disease’;

Tending to infest; acting like an infection.

Having no mirth; not festive or merry; dull; cheerless; gloomy; forlorn.