Long marginalised as a disorder confined to specific racial
Long marginalised as a disorder confined to specific racial groups, sickle-cell disease is now assuming its rightful place as a major global public health problem. Most patients in the Americas, the Caribbean, and much of Europe have been of one racial group, which led to the common misconception that the disease was confined to people of African origin. Indeed, the mutation causing sickle haemoglobin (HbS) was noted on at least three separate occasions in Africa, and the associated polymorphisms are named after the regions where they were first described: Benin, Bantu, and Senegal. A fourth independent occurrence of the HbS gene is shared by people around the Gulf and in India where the prevalence of the trait exceeds 25% in many populations. The relative protection against falciparum malaria conferred by the HbS gene during a critical period of early childhood ensured a survival advantage and increasing prevalence over the generations. From this primary distribution, the gene was carried from west and central Africa to the Americas by the African slave trade, and latterly by voluntary (S)-Methylisothiourea sulfate mostly to the UK and Europe.
The extent and speed of this migration is the subject of an investigation by Frédéric Piel and colleagues in . The investigators combined data from the World Bank\'s Global Bilateral Migration Database of 232 countries with known HbS allele frequencies in the countries from which migration takes place and concluded that migration of individuals with HbS increased from 1·6 million in 1960, to 3·6 million in 2000. The analyses are elegant but assume homogeneity in the distribution of the HbS gene in the donor countries, which might be broadly true in Nigeria, but not in countries such as Uganda and India, in which exist substantial tribal variations in trait frequency. In India, the HbS gene is widespread across Gujarat, Madhya Pradesh, Maharashtra, Chhattisgarh, and Odisha in central India, with a second focus in the north of Tamil Nadu and Kerala in southern India, reaching HbS frequencies as high as 35%; however, the trait is largely confined to the original tribal people living on the Deccan plateau, few of whom will participate in the emigration that traditionally takes place from major cities around the coast.
Notwithstanding these fairly minor concerns, an important implication of Piel and colleagues\' findings is that clinical services for patients will need to be greatly increased in countries with existing expertise, and developed in others without existing services. The structure of these clinical services will be established by local awareness, resources, and expertise. India again has shown that much can be achieved with political will, despite restricted resources, and three states in central India—Gujarat, Maharashtra, and Chhattisgarh—already have sickle-cell control programmes, which have focused largely on population screening and monetary support. The mode of delivery of optimum care is still debated, but there are advantages in dedicated centres providing continuity of care, which can avoid the disruption of transition from paediatric to adult care during which many patients default from regular monitoring just as serious problems such as painful crises, leg ulceration, delayed growth and puberty, priapism, and pregnancy are emerging. Furthermore, a holistic approach to management has advantages, encouraging patients to attend earlier and reducing morbidity.
The World Health Assembly launched the Global Polio Eradication Initiative in 1988 and declared the year 2000 as the target by which to achieve poliomyelitis eradication. After aggressive mass immunisation, backed up by effective routine immunisation, cases of poliomyelitis reduced from 350 000 in 165 countries in 1988 to 355 occurring mainly in three countries—Nigeria, Afghanistan, and Pakistan—by 2013. Nigeria is the only country in the world where the three poliovirus types are still circulating; as of December, 2013, it had contributed 14·1% of all poliomyelitis cases worldwide. In the past 4 years, Nigerian Government and donor investments have increased and traditional leaders have committed to poliomyelitis eradication. Despite all these efforts and many years of mass vaccination campaigns, wild poliovirus continues to circulate in the northern part of the country, leading stakeholders to wonder whether something hidden or unknown is affecting the vaccination programme in Nigeria.