A public health emergency was declared in Pontypridd, South Wales last week following the deaths of three people from meningitis and the treatment of six schoolchildren and four adults in hospital. Medical teams have been carrying out a mass immunisation of pupils in three former mining villages in an attempt to contain one of Britain's worst outbreaks of the disease.

Later, a second public health emergency was declared in another part of South Wales as more cases of meningitis were reported and two more young people were hospitalised.

The outbreak follows on from a series of others in the Northwest and Northeast of England among teenagers and students in university halls of residence. On February 13, a 19-year-old engineering student at Brookes University, Oxford, was taken to John Radcliffe Hospital in the morning and died that same afternoon. The 550 students at his hall of residence have been contacted and a joint action plan drawn up by the university, the student union and Oxfordshire Health Authority to deal with a potential outbreak.

The emergencies have caused widespread anxiety. Many parents are angry that the health authorities did not act earlier, following the death last month of Gareth Gould, a 15-year-old school student. Instead his death was initially treated as an isolated case, and the health authority claimed there was no need to fear an epidemic unless there were a second case. Within 24 hours of Gareth's funeral, more than a week after his death, four children had been rushed to hospital. It is a measure of the severity of the outbreak that school doors opened on a Sunday to enable children to receive antibiotics.

Meningococci are airborne bacteria. They are found at the back of the throat or nose in about 10 percent of the population and in up to 25 percent of young adults in "closed-in" communities such as schools, university residences or military barracks. In such places they have effectively become resident bacteria. Only rarely do they give rise to illness, but when this occurs the illness progresses very rapidly through the blood to the brain. Its symptoms are high fever, headaches, neck stiffness and red spots, which do not blanche under pressure. It is fatal in about one in 10 cases. There have been 150 to 200 deaths a year over the last decade.

Although many people carry the disease, few develop it. But this pool of carriers enables the infection to spread where young people congregate closely together. Most cases are seen in young children, those under four years, with the greatest risk at about six months of age. The next highest incidence is in teenagers between 15 and 19 years of age.

There are several strains of meningitis. Strain A, virtually eradicated in Britain, causes widespread epidemics in sub-Saharan Africa and India, with thousands dead or maimed. Most recently there was an epidemic in the Sudan, which left 300 people dead. Strain B is the most common in Britain. The strain of meningitis thought to be responsible for this epidemic is a relatively new strain of C to A.

Dr. Sergio Brusin, the duty doctor in the Communicable Disease Surveillance Centre at the Public Health Laboratory Service (PHLS) headquarters in London, told the World Socialist Web Site that meningitis is usually associated with crowded and damp living conditions, areas of social deprivation and periods of social unrest. "This is a sub-strain of meningitis type C that has mutated and acquired particular virulence. That's why there has been a higher mortality rate in this outbreak. The incidence of meningitis is unusually high this winter. It is double the baseline rate. We have had 350 cases in the last one and a half months. Usually we would see 180 cases in the same period. It is a dramatic rise. It is the highest in 50 years. Some may be due to better surveillance methods and the new PCR test [the identification of minute quantities of the genetic material of the organism in a blood sample]."

The disease is on the increase in Britain. There are now more cases than at any time since World War II, when there were 11,000 to 13,000 cases per year. The high incidence then was assumed to be caused by the spread of bacteria in air raid shelters.

In the early 1990s there were about 1,200 cases a year, but in 1995 there was a sharp increase in the number of reported cases. Incidences have since doubled to about 2,300 cases a year. Yorkshire, the Northwest and Northeast of England, the old industrial areas with a long legacy of poor quality housing and poverty, have by far the highest rates.

The disease must be treated immediately with antibiotics. But the problem is that the symptoms are not always recognised, being very similar to flu. The gravity of the disease is such that doctors are taught not to waste time going to their car to get antibiotics, but to use whatever they have with them first.

Of those who do survive, almost one-third may be temporarily or even permanently damaged. They may suffer from memory loss and experience difficulty in concentrating. Some have permanent brain damage. Those who contract septicaemia may lose limbs.

According to the PHLS's own guidelines, if only one case has occurred, antibiotics should be given orally to those who had prolonged (more than 24 hours or kissing) contact with the patient. With two or more cases within four weeks (a cluster) in the same play group, nursery or primary school, all children and staff should receive antibiotics. With clusters in secondary schools and colleges, based on local circumstances, public health experts should determine the extent to which antibiotics are offered.

While there is no vaccine for type B infections, there is a vaccine against types C and A. It costs less than 20 cents US an injection when part of a mass immunisation programme, but £5 when bought over the counter at a pharmacist. Mass immunisation programmes against meningitis are a major part of the World Health Organisation's work in Africa. Last year alone 55,000 people were immunised in the Sudan and 20,000 in Niger.

The vaccine is of little use for infants but does provide three to five years immunity for older people, although less for younger children. The authorities have justified not using it on the grounds that it is not suitable for a general programme of immunisation like polio, measles and diphtheria.

However the PHLS explains that it can be used to control an outbreak of type A or C in high-risk populations. Some doctors are now calling for a widespread programme of vaccination in South Wales to control the infection's spread.