Ich kenne das nur mit Possessivpronomen:

Ihr Lachen ist ansteckend. = Her laughter is contagious / infectious.

Die Variante mit Substantiv (#1) ist korrekt.

The contagious laugh effect contributes to the laugh-producing property of “laugh boxes,” “laugh records” such as that produced by ...

Social Learning In Animals - Google Books

Das wird auch in einsprachigen englischen WB erwähnt, hier am Beispiel von Merriam-Webster (MW) :

https://www.merriam-webster.com/dictionary/co...

  contagious adjective

con·​ta·​gious | \ kən-ˈtā-jəs \

Definition of contagious

 ... 4 : exciting similar emotions or conduct in others contagious enthusiasm contagious laughter ...

 ... Both contagious and infectious are also used figuratively, often in much happier contexts: laughter can be contagious; someone's enthusiasm can be infectious. While both words are used figuratively of both pleasant and unpleasant things, contagious is more often chosen for the unpleasant, as when it's grumpiness or fear that seems to be spreading. ...

 ... : causing other people to feel or act a similar way a contagious laugh ...

#3: Damit keine Missverständnisse aufkommen: andere syntaktischen Varianten sind deswegen nicht "inkorrekt", z.B.

Deputy Headteacher Sally Heppenstall added: “I will remember Adam for his infectious laugh.

Heartbreak over death of 'popular' 14-year-old boy with an 'infectious laugh' | The Bolton News

As a BE NES my first thought was "infectious laugh" - certainly not incorrect and what I would say myself.