The World Health Organization called Wednesday for people infected with monkeypox to avoid exposing animals to the virus following a first reported case of human-to-dog transmission.

A first case of human-to-dog transmission of monkeypox -- between two men and their Italian greyhound living together in Paris -- was reported last week in the medical journal The Lancet.

"This is the first case reported of human-to-animal transmission... and we believe it is the first instance of a canine being infected," Rosamund Lewis, the WHO's technical lead for monkeypox, told reporters.

Experts, she said, had been aware of the theoretical risk that such a jump could happen, and that public health agencies had already been advising those suffering from the disease to "isolate from their pets".

In addition, she said "waste management is critical" to lower the risk of contaminating rodents and other animals outside the household.

It was vital, she said, for people to "have information on how to protect their pets, as well as how to manage their waste so that animals in general are not exposed to the monkeypox virus."

- Could mutate -

When viruses jump the species barrier it often sparks concern that they could mutate in a more dangerous direction.

Lewis stressed that so far there was no reports that was happening with monkeypox.

But, she acknowledged, "certainly as soon as the virus moves into a different setting in a different population, there is obviously a possibility that it will develop differently and mutate differently."

The main concern revolves around animals outside of the household.

"The more dangerous situation... is where a virus can move into a small mammal population with high density of animals," WHO emergencies director Michael Ryan told reporters.

"It is through the process of one animal infecting the next and the next and the next that you see rapid evolution of the virus."

He stressed though that there was little cause for concern around household pets.

"I don't expect the virus to evolve any more quickly in one single dog than in one single human," he said, adding that while "we need to remain vigilant... pets are not a risk."

Monkeypox received its name because the virus was originally identified in monkeys kept for research in Denmark in 1958, but the disease is found in a number of animals, and most frequently in rodents.

The disease was first discovered in humans in 1970 in the Democratic Republic of Congo, with the spread since then mainly limited to certain West and Central African countries.

But in May, cases of the disease, which causes fever, muscular aches and large boil-like skin lesions, began spreading rapidly around the world, mainly among men who have sex with men.

Worldwide, more than 35,000 cases have been confirmed since the start of the year in 92 countries, and 12 people have died, according to the WHO, which has designated the outbreak a global health emergency.