infectious

What it means

1. medicineCaused by an agent that enters the host's body (such as a bacterium, virus, parasite, or prion); often, also, transmitted among hosts via any of various routes (for example, contact, droplet-borne, airborne, waterborne, foodborne, fomite-borne, or bloodborne).

   Cancer is usually not infectious.

   1 more example

   More infectious diseases like the flu are usually less potent.

2. typically of a personmedicineAble to infect others; capable of transmitting pathogens.

   Despite feeling better, the patient is still infectious.

   1 more example

   I doubt that [saliva] is very infectious ... I don't think this is a normal route of transmission.

   1981 December 1, Sue Hyde, quoting Paul Black, “AIDS Update: Little To Cheer About”, in Gay Community News, volume 12, number 20, page 3

3. Spreading quickly from one person to another.

   infectious smile

   2 more examples

   Her enthusiasm for work can be really infectious.

   When Maisie first met Danny, she remembers that he had an infectious laugh and a love for music.

   2024 November 20, Fortesa Latifi, “How These Men Left the Manosphere — and Why Some May Never”, in Teen Vogue

In a sentence

Cancer is usually not infectious.

Where it comes from

1. New Latinīnfectiōsus
2. Englishinfectious

Borrowed from New Latin īnfectiōsus. By surface analysis, infect + -ious.