A leprosy outbreak could soon hit homeless populations in the US, a doctor has warned.

Dr Marc Siegel, of New York University's Langone Health, fears it is just a 'matter of time' before the bacterial disease strikes.

He pointed to Los Angeles County as being particularly at risk, with almost 60,000 people sleeping rough in the area.

Although leprosy is not particularly contagious, the combination of poor hygiene, a lack of shelter and inaccessible medical treatment among the homeless creates a 'perfect cauldron' for the disease, Dr Siegel said.

Left untreated, the infection can cause blindness or permanent disability - a 'sure recipe for instant public panic'.

Dr Siegel is speaking amid the re-emergence of 'Middle Ages' diseases' in the US, with LA also experiencing a typhus outbreak at the beginning of the year.

A leprosy outbreak could hit the homeless in the US, an expert has warned (stock)

Leprosy, or Hansen's disease, affects 250,000 people worldwide every year, according to the Center for Disease Control and Prevention (CDC).

Two thirds of these cases are in India, which is home to one third of the world's poorest people, Dr Siegel wrote in The Hill.

Central and South America have more than 20,000 new incidences a year, with 'sporadic cases continuing to be brought across our southern border undetected', he added.

Even in developed countries like the US, 150 people are diagnosed with leprosy every year, CDC statistics show.

Once thought to be highly contagious, leprosy is actually hard to spread and easy to treat once diagnosed.

A study by the University of Southern California looked at 187 leprosy patients between 1973 and 2018.

Scientists found an average three year delay in diagnosis, by which time side effects, some of which were irreversible, had already taken hold.

Dr Siegel worries LA's homeless population, of which three quarters lack medical treatment, would be particularly vulnerable.

'It seems only a matter of time before leprosy could take hold among the homeless population in an area such as Los Angeles County,' he wrote.

'[It has] close to 60,000 homeless people, [of which] 75 per cent lack even temporary shelter or adequate hygiene and medical treatment.

'All of those factors make a perfect cauldron for a contagious disease.'

Dr Siegel claims he is most concerned about the permanent disabilities leprosy can cause, rather than its stigma.

But he added: 'Leprosy appearing among the homeless in LA is a sure recipe for instant public panic.

The bacteria behind the infection, Mycobacterium leprae, attacks nerves in the body, which can lead to the characteristic 'peeling' skin.

Untreated, this can cause paralysis of the hands and feet. A lack of sensation in the body may also lead to multiple injuries, with damaged fingers and toes even being reabsorbed by the body.

Eye ulcers and blindness can occur if the facial nerves are affected.

Dr Siegel's concerns come after typhus swept LA County, infecting a city hall prosecutor and more than 100 others.

Officials recorded 124 cases of the disease in the county last year, with the homeless being particularly hard hit. Just 67 cases were recorded in 2017.

Flea-borne typhus occurs when faeces from an infected insect come into contact with a person's cut or gets rubbed into their eyes.

These fleas often live on feral cats and rats who are attracted to areas with rubbish on the streets.