Monkeypox could have a “massive impact” on access to UK sexual health services, a leading doctor has warned.

Dr Claire Dewsnap, the president of the British Association for Sexual Health and HIV, has voiced concern about how the viral infection could affect services as staff who come into contact with sufferers are forced to isolate.

She told the BBC that clinic staff were already under significant pressure before monkeypox was identified. “It is already stretching the workforce and will have a massive impact if staff have to isolate if they are in close contact with someone who’s infected,” she said.

As of Friday, there were 20 confirmed cases of the disease in the UK, and nine other countries outside central and west Africa have also reported outbreaks.

Monkeypox, which was first detected in 1958, can be transmitted from person to person through close physical contact.

Dewsnap told BBC Radio 4: “In terms of the infection and its consequences for individuals, I’m not that concerned, but I am concerned about our ability to maintain good sexual health services and access for everyone while still managing this new infection.”

She called for “adequate funding” for sexual health services that she said had experienced cuts to their budgets over the past decade, adding that the ability to see people quickly was important when dealing with infection.

“Over the last 10 years, there’s been a significant decrease in funding through the public health budget, and that has seen a direct effect on staffing level and that means we have less capacity to see people,” she told BBC Breakfast.

“We used to be able to see people within 48 hours of them contacting us – that’s really important because it cuts down the window where people have an infection [while] they don’t know they have an infection and therefore they can pass it on to people.

“So, the speed in which we see people is really critical, and monkeypox coming along shows us that more than ever before.”

She said proper funding would mean they could “ensure people can get in quickly, and therefore we can reduce the risk of infection of other people”.

Meanwhile, Prof Sir Peter Horby, the director of the Pandemic Sciences Institute at the University of Oxford, described the monkeypox outbreak as “an unusual situation” because the virus is being transmitted within communities outside central and west Africa.

“It’s transmitted by close person-to-person contact and in the past we have not seen it being very infectious,” he told BBC Radio 4’s Today programme.

“What’s unusual about what we’re seeing now is that we’re seeing transmission occurring in the community in Europe and now in other countries, so it’s an unusual situation where we seem to have had the virus introduced but now have ongoing transmission within certain communities.”

He added: “It would appear that there is some element of sexual transmission, perhaps with just the very close contact between people and the skin lesions, because a large proportion of the current cases are being detected in gay and bisexual men.

“So it’s very important that we get the message across that if people have unusual skin lesions that they do seek attention quickly so that we can control this.

“The important thing is that we interrupt transmission and this doesn’t become established in the human population in Europe.”

The UK Health Security Agency has said the infection can be transmitted through “close contact or contact with clothing or linens used by a person who has monkeypox”.

However, it added that the virus does not usually spread easily between people and the risk to the UK population “remains low”.

Symptoms of monkeypox include fever, headache, muscle aches, backache, swollen lymph nodes, chills and exhaustion.

A rash can develop, often beginning on the face, then spreading to other parts of the body including the genitalia. The rash then changes and goes through different stages – and can resemble chickenpox – before finally forming a scab, which later falls off.

According to the NHS, symptoms are usually mild and clear up in “two to four weeks”, although severe cases can sometimes occur.

The UK government has said it is stocking up on smallpox vaccines to help guard against monkeypox.