It comes as ministers spoke of plans to put potential sufferers into isolation after a rise in the number of infections among those coming to the UK.
The immigration minister told MPs that migrants showing signs of the highly-contagious disease will be separated for a “short period” at the Manston processing centre in Kent or held in “secure isolation hotels” while they are treated.
Any asylum seekers who may have the infection but are already in hotels will be told to isolate in their rooms while they are treated, Robert Jenrick said.
It was revealed that there had been diphtheria cases in the West Midlands, but gave no other details other than to say there had been “fewer than five” cases.
The latest Health Security Agency (UKHSA) report said the region had identified cases along with the South West, North East and the North West. It declined to give a further breakdown of where the cases were identified.
The majority of cases – 38 – were reported in the South East, where most migrants first make themselves known after crossing the English Channel by small boats.
At least 22 hotels in the West Midlands are currently being used to temporarily house asylum seekers despite a Home Office pledge to end the practice. One hotel is used solely for unaccompanied children, while at others groups of asylum seekers have been put up for more than six months. At least three prominent hotels are currently in talks over taking in asylum seekers. The hotels are not being identified for security reasons, but many are in prime town and city centre locations in the Black Country.
It was also revealed earlier this month that a hotel in Shrewsbury asked paying guests to leave because it was being closed in order to take in asylum seekers.
The revelations about the diphtheria outbreaks come after Home Secretary Suella Braverman faced criticism about overcrowding and outbreaks of disease at Manston, and the Home Office said a man held there may have died from a diphtheria infection.
The UK Health Security Agency (UKHSA) said there had been an “increase” in cases of diphtheria reported among asylum seekers arriving in the UK, with 50 identified as of November 25 including children. The figure stood at 39 on November 10.
Meanwhile, Channel crossings resumed, with more migrants pictured arriving on the Kent coast.
Mr Jenrick told the Commons: “From today, no-one presenting with symptoms will progress into the asylum accommodation system.
“They will either remain at Manston, isolating for a short period, or they will travel to a designated isolation centre in secure transport where they will be treated until deemed medically fit.”
Mr Jenrick later confirmed the isolation centres would be “secure isolation hotels”, such as those used during the coronavirus pandemic, and that migrants would then be moved to other accommodation once they had made a full recovery.
The level of infectious diseases in migrant camps in northern France is also being assessed, he added.