Regarding the claim that scratching is a "No Risk" activity, here is a study showing no HIV transmission from scratches and bites from a person with contaminated fingers and mouth:
To examine the relative risk of transmission of the human
immuno-deficiency virus (HIV) through bites and scratches, we studied
198 health care workers, 30 of whom were traumatized in this fashion
while caring for an aggressive AIDS patient. This violent patient
frequently bit or scratched others, his mouth had blood and saliva,
while his fingernails were at times soiled with semen, feces, and
urine. He was HIV antibody and antigen positive. Although HIV was
recovered from his peripheral blood lymphocytes, after 2.5 years of
serial follow-up, all traumatized personnel were clinically normal, no
HIV was cultured from their blood, and all were HIV antibody and P24
antigen negative. We conclude that this viremic AIDS patient, while
producing copious amounts of body fluids, failed to infect those
caring for him through bites and scratches. The risk of transmission
of HIV through this route under similar conditions should be low.
Tsoukas et al, 1988. Lack of transmission of HIV through human
The CDC rates the risk for transmission from broken skin or wounds and infected blood as extremely rare, and the risk of transmission from scratches as none:
In extremely rare cases, HIV has been transmitted by
- Contact between broken skin, wounds, or mucous membranes and HIV-infected blood or blood-contaminated body fluids.
Can I get HIV from being spit on or scratched by an HIV-infected person?
No. HIV isn’t spread through saliva, and there is no risk of transmission from
scratching because no body fluids are transferred between people.
But extremely rare of course doesn't mean that there are no cases, which would make the claim that ""No one has ever transmitted HIV through wound to wound contact" false:
We report a case of HIV-1 infection transmission caused by a fist
fight between brothers.Emerson & Quah, 2008. Transmission of
HIV-1 infection due to a fist
To put that into perspective:
For those of us who work in the health care arena, the chances of
transmission through splashes of blood, a knife or a needle are more
likely than in sports and you still don't see a lot of cases, although
it's not zero.
In boxing, the wounds can happen dramatically and
quickly. But the risk is still very, very small. LA Times,
1996. Boxer's HIV Test Heats Up Debate Over Risk to Others
And here is an article about HIV transmission during sport in general:
There are no confirmed reports of HIV transmission during
sport.Kordi & Wallace, 2004. Blood borne infections in sport:
risks of transmission, methods of prevention, and recommendations for
I would conclude that scratching is indeed a no risk activity, while being beaten to a bloody pulp is a low risk activity.
To your point about excluding players due to their HIV status: If the player is receiving proper medical care and their viral load is suppressed, the change of infection even for high risk activities is low, for low risk activities it is essentially none.