The latest clinical reports leave little doubt as to how the monkeypox virus is spread.
"Our study strengthens the evidence for skin-to-skin contact during sex as the dominant mechanism of transmission of monkeypox, with important implications for disease control," said The Lancet with data from several Spanish hospitals.
Nearly 28,000 cases have been confirmed worldwide in the last three months and the first deaths are starting to be recorded.
Monkeypox has been around in a dozen African countries for decades, but in contrast to previous outbreaks on the continent, the virus is now predominantly spread through sexual activity.
Some 99 percent of US cases have so far been among men who have sex with men (MSM). In Africa, the virus notably affects children.
The male sex link was no surprise as it appeared from the first recorded observations and has been targeted by health authorities.
The viral charge had been found to be much higher in patients' skin lesions than in their breathing equipment.
This observation seems to undermine the idea pushed by some researchers that airborne transmission was also playing a major role in the spread of cases.
At the same time monkeypox is not thought to be caught via sperm, and although that has not been totally ruled out, current research is far from proving it.
The Lancet found complications occurred in 40 percent of cases and the NEJM in some 20 percent.
But there was also some good news about the gravity of the illness.
"Clinical outcomes in this case series were reassuring. Most cases were mild and self-limited, and there were no deaths," the NEJM said.
"Although 13 percent of the persons were admitted to a hospital, no serious complications were reported in the majority of those admitted."
