Meningitis: Tackling a Global Threat
SummaryDespite the media publicity that meningitis attracts when there is an outbreak, it remains one of the most serious infectious diseases facing the world - affecting populations in affluent and poorer countries alike.
Meningitis is an inflammation of the meninges, the thin lining that surrounds the brain and the spinal cord. The most common symptoms of meningitis are stiff neck, high fever, sensitivity to light, headaches and vomiting.
Although viruses and fungi can also cause the disease, it is bacterial meningitis that causes greatest concern because it is considerably more severe and can be fatal. Meningococcal bacteria are one of the main causes of bacterial meningitis. When meningitis occurs along with septicaemia (blood poisoning) it is referred to as meningococcal disease.
Several different types of meningococcal bacteria can cause meningococcal disease, but the World Health Organization (WHO) considers Neisseria meningitidis to be one of the most important because of its potential to cause epidemics (1, 2). Twelve subtypes or serogroups of N. meningitidis have been identified and four (N. meningitidis A, B, C and W135) have been linked to epidemics of meningococcal disease (1). Other bacteria such as Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae are also one of the most frequent causes of meningitis (2).
The early diagnosis and treatment of meningococcal disease are very important as the onset of the disease is sudden and death can follow within hours. Furthermore, it is spread by person-to-person contact through the respiratory droplets of infected people or asymptomatic carriers, which increases the chances of a major outbreak. Thus, WHO recommends that meningococcal disease should always be viewed as a medical emergency (2). It is one of the rare conditions where general practioners could administer penicillin prior to the ambulance.
Around 80% of bacterial meningitis patients are children below 2 years of age, although the disease can affect older children and adults – particularly the elderly. Bacterial meningitis can be treated with a number of effective antibiotics, provided that the intervention is early enough.
Several vaccines are also available and many believe that vaccination offers the best hope of combating the disease. However, the lack of a vaccine that provides long-term protection from the disease is one reason why few countries have established mass vaccination programmes. Many countries only vaccinate after cases have been confirmed by a laboratory or when reported cases rise above a certain threshold. WHO takes this to be 15 cases per 100,000 population/week, averaged over two weeks (3).
Meningitis outbreaks occur throughout the world, with seasonal variations being responsible for much of its appearance. In temperate regions the number of cases tends to increase in winter and spring. In some regions the increase of cases is so consistent that it almost has an endemic profile. An outbreak is considered to be an epidemic when there have been 100 cases per 100,000 population over several weeks (4).
There have been a number of meningitis outbreaks across the world, with one of the first detailed descriptions being from 1805, when an epidemic occurred in Geneva, Switzerland (1). However, the region that continues to experience the largest outbreaks is Africa, but media coverage of these epidemics has been low. The highest burden of disease has been in an 18-country region which stretches from Senegal to Ethiopia and encompasses a total population of 300 million people (1, 4). This has led to the region being known as the African “meningitis belt.” Population overcrowding and local weather conditions have increased the risk of the disease spreading (1, 4). Meningitis is a public health issue rather than a medical one as improvements in areas such as sanitation and housing would reduce the danger posed by the disease.
In 1996, the region experienced the largest single recorded outbreak of epidemic meningitis in history, with over 250,000 cases and 25,000 deaths registered (1). Further epidemics have occurred since this period and according to WHO, there are indications that the African meningitis belt is extending further south (1).
The scale of the continuing problem in Africa is an issue that has highlighted the disparities in healthcare between affluent industrialised countries and those classed as developing regions. WHO has been attempting to monitor the African situation, but up to date and regular information on outbreaks in certain countries is difficult to gather and to interpret in a meaningful manner.
Cooperation for drug development and disease prevention
Meningitis is a therapeutic area that has seen growing cooperation between governments and the industry. For example, in the USA, the Pharmaceutical Research and Manufacturers of America (PhRMA), the FDA (Food and Drug Administration) and the Infectious Diseases Society of America (IDSA) held a joint meeting in November 2002 to look at the issues affecting drug development for meningitis (5). The meeting addressed issues such as the study design and the interpretation of data for appropriate meningitis clinical trials.
At an international level, following the disastrous 1996 epidemic in Africa, the International Coordination Group (ICG) was established in January 1997. The ICG members include WHO and UN agencies, international aid organisations, vaccine and syringe manufacturers and aims to improve the international response to meningitis epidemics (6). The ICG ensure rapid and equal access to vaccines, injection material and oily chloramphenicol, and builds up stocks of these items (1, 4, 6). The group meets annually in September to review the progress over the preceding year, take account of any new developments in the field and make recommendations in preparation for the next meningitis season in Africa. The ICG has had to work hard because during an epidemic in 2001, there was a shortfall in vaccine stocks (7). Nevertheless, WHO believe that vaccination of populations in regions at risk offer the best strategy to tackling the disease on a global basis (1).
Meningitis remains a deadly disease, but concerted and coordinated international action can have a dramatic impact on improving the prospects for those in affected regions. As well as increasing the availability of vaccines and treatments, improvements must be made in public health if governments and aid organisations are to be successful in halting the spread of the disease.