April 24th is World Meningitis Day. The disease, which affects the protective membranes lining the brain and spinal cord, is unfortunately back in the news these days. It is no coincidence that this year’s Day also coincides with the alarm issued by the US Centers for Diseases Control about a significant increase in the number of cases of invasive meningitis with a rising fatality rate. The World Health Organisation (WHO) has developed a global programme to defeat meningitis by 2030 based on three objectives: elimination of bacterial meningitis epidemics; reduction of bacterial meningitis cases and thus cases of deaths caused by the disease, which can be prevented by the use of vaccines (up to 50 per cent fewer cases); reduction in the number of disability cases and improvement of quality of life after meningitis due to any cause.
Giuseppe Ippolito, Professor of Infectious Diseases at UniCamillus University, in his 20 years as Scientific Director of the National Institute for Infectious Diseases ‘Lazzaro Spallanzani‘ in Rome and later as Director of the WHO Collaborating Centre for Highly Infectious Diseases, has had the opportunity to study this disease very closely.
Professor, we know that meningitis generally has an infectious origin, but what are the main agents that cause it?
“Meningitis is an inflammation of the protective membranes of the brain and spinal cord that can affect people of any age. It originated in Sub-Saharan Africa but has spread over the years to several areas in Asia and South America as well. In 1963, a WHO official observed that the disease occurred in areas where 300 to 1100 mm of average annual rainfall occurred. It was from there that the study on the intercontinental spread of meningitis began. There are four main agents of bacterial meningitis that are responsible for more than half of all meningitis deaths globally and cause other serious diseases such as sepsis and acute pneumonia: Neisseria meningitidis (meningococcus), which has many types; Streptococcus pneumoniae (pneumococcus); Haemophilus influenzae; Streptococcus agalactiae (group B streptococcus); and Listeria monocytogenes.
Other bacteria such as Mycobacterium tuberculosis, Salmonella, Listeria, Streptococcus and Staphylococcus, viruses (such as enterovirus and mumps, herpes), fungi (especially Cryptococcus), and parasites such as amoeba, are also important causes of meningitis.
Bacterial meningitis is the most common and dangerous and can be fatal within 24 hours. This is why early identification, isolation and immediate treatment are necessary. Viral meningitis is more frequent in summer. There is also non-infectious meningitis associated with malignant tumours, subarachnoid haemorrhage, chronic inflammatory disease and certain drugs.”
How dangerous is meningitis and how is it transmitted?
“Meningitis is still one of the major global public health challenges in the world today. Approximately 1 in 6 people who contract it die and 1 in 5 experience serious long-term complications. The route of transmission varies depending on the micro-organism. The bacteria that cause meningitis are transmitted from person to person through the droplets of respiratory or pharyngeal secretions of carriers. Close and prolonged contact, such as kissing, sneezing or coughing on someone, or living in close contact with an infected person, facilitates the spread of the disease. The average incubation period is 4 days but can vary between 2 and 10 days.”
However, not all agents that transmit it are the same…
“No. Most of the bacteria that cause meningitis such as meningococcus, pneumococcus and Haemophilus influenzae are present in the nose and throat of humans. Neisseria meningitidis, for example, only infects humans and a significant percentage of the population (between 5 and 10%) carries it in the throat. It mainly affects children and young adults. Then there is pneumococcal meningitis, prevalent in adults and the elderly, which is transmitted by the respiratory route in a sporadic form and circulation is ancillary to localisation of the upper respiratory tract or ear.
Meningitis transmission can also occur from mother to child at birth, because group B streptococcus is often carried in the vagina (the same bacterium is also present in the gut). Listeria monocytogenes meningitis, on the other hand, has a food-borne mode of contagion and is more frequent in elderly individuals and those with deficient cell-mediated immunity, such as patients with acute or chronic haematological diseases.”
How do infection numbers vary in different parts of the world where meningitis is widespread?
“Firstly, carriage of the organisms that transmit meningitis is usually harmless and even helps individuals develop immunity against infection. Occasionally, however, the bacteria invade the body, causing meningitis and sepsis. Official data on the spread of the disease shows a particular concentration of cases in some of the poorest, but climatically diverse areas of the world. There is in fact no accurate count of the number of meningitis cases, despite the fact that surveillance systems provide for mandatory reporting in many countries. It is estimated that there are at least 300,000 deaths a year from meningitis worldwide. The main areas, albeit with different frequencies, are Africa, northern India, parts of Pakistan, Mongolia, parts of Yemen, Saudi Arabia, Brazil and the west coast of South America. In the remaining part of the planet, sporadic cases occur.”
What are the risk factors that can trigger meningitis outbreaks?
“The risk factors for meningococcal disease outbreaks in Africa, as in other areas, are not fully understood. However, some specific conditions seem to be particularly favourable elements for the disease. These include dry and dusty conditions during the dry season (particularly in Africa) between December and June, immunological susceptibility of the population, travel and large population movements, and crowded housing conditions. Another finding is that in temperate regions the number of cases increases in winter and spring.
Important information about contagion and spread comes from the analysis of Neisseria meningitidis serogroups. The annual Hajj pilgrimage, which brings millions of Muslim worshippers to Mecca, has also been associated with outbreaks of meningococcal disease due to serogroups A and W. In Europe, the Americas and Australia, serogroups B, C and Y together account for the vast majority of cases. An increasing number of serogroup W strains have been recorded in some areas. The distribution of serogroups shows significant differences in the local distribution of causes of bacterial meningitis. For example, while Neisseria meningitidis serogroups B and C cause the majority of disease outbreaks in Europe, group A is found in Asia and continues to predominate in Africa, where it causes most of the major outbreaks in the meningitis belt, accounting for about 80% of meningitis cases.”
What, on the other hand, do the figures in Italy and Europe say?
“In Europe there are more than 1,000 confirmed cases of invasive meningococcal disease annually, the only one with good epidemiological surveillance coverage, with a fatality rate of 10%. In Italy, the Ministry of Health’s National Surveillance System for the three main forms of meningitis reports an incidence of 0.1 cases per 100,000 inhabitants for meningococcus, 1.74 for Streptococcus pneumoniae, 0.32 for haemophilus, and 0.15 for listeria monocytogenes.”
Elderly people and children are the most exposed to infection: what are the main weapons to prevent the disease?
“Although meningitis affects all ages, young children are most at risk. In particular, infants are most at risk of group B streptococcus, toddlers are at greatest risk of meningococcus, pneumococcus and Haemophilus influenzae. Adolescents and young adults are particularly at risk of meningococcal disease while the elderly are particularly at risk of pneumococcal disease. The only weapon is prevention and early diagnosis. Today, we have safe, effective and free vaccines at our disposal, as established by the new national vaccination prevention plan, which has expanded its free offer to all the age groups. Haemophilus B meningitis, typical of children in the first five years of life, has been drastically reduced with the introduction of compulsory vaccination with the hexavalent vaccine. In all cases, early diagnosis is important for prognosis of the disease. If meningitis is suspected, the patient should be immediately referred to hospital.”