Health: It was like a slap in the face: Parents can be taken aback when GPs diagnose a common childhood rash, says Deborah Jackson

WHEN the doctor told David Jones that his son had 'slapped cheek disease', David thought it was a bad joke. Simon, aged seven, had raw-looking cheeks and a rash with a lacy pattern over his legs. His father did not believe that slapped cheek disease could be a genuine medical diagnosis.

'I thought the doctor was implying that I had done it,' said Mr Jones, from Peckham, south London. 'But she reassured me that it is quite a common disease in children, which refers to the fact that the face looks as if it has been slapped. Simon just needed to stay off school and rest.'

When a child develops a rash, parents are apt to hasten to the medical books, expecting that measles, chicken pox or German measles are about to erupt. They may be surprised to learn that not every red spot is a measle and that researchers still do not know what causes many rashes. GPs tend not to bother doing blood tests on children with rashes: by the time the results come through the child will probably be better anyway.

'There are so many viruses that cause rashes. You only do blood tests if there is a worry about pregnancy,' said Jill Bartlett, a GP in St Albans, Hertfordshire.

Slapped cheek disease is sometimes confused with other childhood illnesses, especially in their mild forms or early stages. It is easily mistaken for rubella (German measles).

At County Bridge Primary School in the West Midlands an outbreak earlier this year was at first confused with allergy by local GPs, according to the headteacher, Rod Lloyd-Davies. 'Suddenly we had 15 or 16 cases of 'allergies',' he said. 'But our community health consultant was at the school when an infected child walked in - she immediately diagnosed slapped cheek disease.'

Dr Bernard Cohen, a clinical scientist with the Virus Reference Laboratory at the Central Public Health Laboratory in London, has studied Parvovirus B19, which is responsible for slapped cheek disease. The virus was discovered in 1975 during the screening of healthy blood donors for hepatitis B. But slapped cheek disease has been known by its symptoms for far longer. It is also called Fifth disease, a name that arose from early research into childhood rashes, Dr Cohen explained.

'Between 1850 and 1880, German physicians set about identifying the rashes and numbering them. Slapped cheek, or erythema infectiosum, was named Fifth disease and is still called that today.

'First disease was scarlet fever, Second was measles, Third was rubella and Sixth was Roseola infantum, a rash in young babies accompanied by a fever,' Dr Cohen said. 'Fourth disease was probably a mistake. It was called Duke's disease, after a Dr Duke who identified it, but people now believe he was probably looking at rubella. All these rashes can be confused.'

Christopher Robin, we may recall, confused his doctors in just such a way, when his 'Sneezles' brought the professionals scurrying to his bedside. 'They examined his chest for a rash and the rest of his body for swellings and lumps,' wrote A A Milne. Next morning, the mystery virus had 'vanished away'.

Childhood rashes are rarely troublesome for the healthy child, who may at worst feel under the weather for a few days. The problem is for those vulnerable members of the community whose systems cannot cope with the attacking virus. Children are often infectious for some time before any rash appears.

German measles is known to be dangerous to women in early pregnancy, as it can cause congenital defects, cataracts and even deaf-mutism in the unborn child. What is not so well known is that slapped cheek disease may also be a threat to the foetus, as Parvovirus B19 can cross the placenta. Infections in adults, especially women, may be accompanied by acute arthritis. For sufferers of sickle cell disease, the virus can cause a crisis of their condition. Vaccines against Parvovirus B19 are not yet available.

Doctors usually advise that children with slapped cheek disease should stay at home until the rash clears. If infection reaches a school, up to 60 per cent of the children may be affected, some without any apparent symptoms.

'Tests for Parvovirus B19 are not widely available at present,' Dr Cohen said. 'The virus is very difficult to grow, and there are some technical problems. Nevertheless, more and more laboratories are able to do the test and we have reports of outbreaks all over the British Isles.'

The disease, he said, has a peak in the first half of the year, often in April and May. 'Some years there is a much bigger peak than others and this year looks like one of those. This is an epidemic year for slapped cheek disease.'

(Photograph omitted)