The infections pose an “extremely low risk” to the general public, Transport Secretary Mark Harper stressed, despite migrants being taken from overcrowded facilities to hotels across the country.
He defended the government’s handling of people who have crossed the Channel in small boats before officials are expected to confirm the number of infections has risen to around 50.
The Home Office said the death of a man who may have been unlawfully held at the Manston center in Kent for a week could be from diphtheria infection.
Mr Harper told Sky’s Sophy Ridge on Sunday: “There is an extremely low risk to the wider community in relation to the diphtheria issue, it is a disease which is of course vaccinated in the standard childhood vaccination pack.
“We take the well-being of the people in our care very seriously. As far as I know these cases were people who had this disease before coming to the UK.”
He insisted the UK Health Security Agency (UKHSA) is working “very closely” with the NHS “to ensure we look after the people who have been diagnosed with diphtheria to ensure they receive the treatment and care , that they need”.
The man being held in Manston died in hospital on November 19. He is believed to have entered the UK on a small boat seven days earlier.
As of November 10, the UKHSA had identified 39 cases of diphtheria in asylum seekers in England in 2022. But on Monday it is announced that the number will rise to about 50.
Initial tests on the man at a hospital near the center, where Home Secretary Suella Braverman has been criticized for overcrowding and outbreaks of disease, came back negative.
The government said on Saturday that a subsequent PCR test indicated that “diphtheria could be the cause of the disease”.
Public health officials have raised concerns about the spread of the highly contagious disease as people were moved from the facility to hotels.
According to the Sunday Times, Jim McManus, president of the Association of Directors of Public Health, said this situation “could and should have been prevented”.
A government spokeswoman said: “Our thoughts are with the family of the deceased man and all those affected by this loss.
“Initial test results processed by a local hospital for an infectious disease were negative, but a subsequent PCR test was positive, suggesting diphtheria could be the cause of the disease. The coroner will conclude in due course.
“We take the safety and well-being of those in our care very seriously and are taking whatever steps are necessary based on these results.”
Diphtheria vaccinations will be offered to all newcomers to Manston, the spokeswoman said, although the facility is currently empty.
An autopsy and forensic examination are ongoing.
Diphtheria is a highly contagious infection that affects the nose, throat and sometimes the skin. The NHS says it’s rare in the UK and can be treated with antibiotics and other medicines.
At one point up to 4,000 people were being held at Manston, which is only designed for 1,600 people, but on Tuesday government sources said the compound had been cleared.
New arrivals were expected to be taken to the centre, which is designed to hold people for short periods during security and identity checks before being transferred to accommodation.
However, some people have been held for much longer periods due to a lack of alternative housing.
As migrants have been moved from Manston to hotels across the country, health officials are advising people to be offered vaccinations and preventive antibiotic courses upon arrival at their new accommodation.
The UKHSA warned that shelters should be considered “high risk of infectious diseases”.
Want a quick, expert briefing on the biggest news? Listen to our latest podcasts to find out what you need to know