The latest is scabies, in which tiny parasites burrow under the skin and lay eggs, causing severe irritation. Its incidence has more than doubled in five years, and there are now an estimated 3,800 cases a year in Britain.
It is passed through skin-to-skin contact and outbreaks have been reported in geriatric and psychiatric wards, junior schools, Aids units and residential homes for the elderly. In the largest hospital outbreak, 17 patients and 20 members of staff were found to have the disease.
Ignorance of diseases when they become rare may be one reason for their re-emergence, experts say. They are not easily recognised by sufferers or doctors, which helps those which are infectious to spread.
Researchers from Ruchill Hospital, Glasgow, warned last week that polio could reappear. After looking for antibodies against it in a group of patients with hepatitis A, they found that a only a third would be able to resist one of three polio virus strains.
Ignorance would account for the recent case of a teenager from Northern Ireland who caught scurvy because her diet of junk food led to severe vitamin C deficiency. The disease results in a rash over the body and bleeding gums, and can be fatal. The teenager rarely ate fruit or vegetables, preferring crisps, chocolate, burgers and cola.
Scurvy is not infectious, but tuberculosis and diphtheria are. TB rates are causing alarm in America and parts of Europe. In Britain, the rate of decline has levelled off and is being closely monitored by the Public Health Laboratory Service (PHLS). In New York, the TB crisis, particularly linked to HIV infection, has led officials to revive 19th-century laws under which patients can be locked up until they are cured.
This month the Communicable Disease Surveillance Centre, part of the PHLS, advised all health workers who might travel to Russia to boost their immunisation against diphtheria. Some 4,000 cases were reported there last year.
Experts point out that infectious diseases thought to belong to another age will always threaten while they exist somewhere in the world. Increased travel is a major factor in their re-emergence. With TB, the incidence tends to be highest in those who spend time in Asia or Africa.
So far, British inoculation programmes have been effective. There has been no 'wild virus' polio for 10 years in Britain and no death of a child from measles for three. The handful of polio cases that arise are caused by the vaccine.
Dr David Salisbury, principal medical officer at the Department of Health, said that vigilance and education to maintain high levels of vaccination were vital. 'When there is no public awareness of the importance of a disease, it is quite hard to maintain the public's interest and enthusiasm in preventing it. For example, there is still some fear of polio, but measles is seen as a much less serious disease, yet it kills 1.4 million worldwide, every year.'Reuse content