**2.2 Circulating genotypes and clades in Africa**

Measles virus is monotypic; however, genetic variations occur in the H and NP genes. Currently, the WHO recognizes 8 clades, A-H which consists of 24 genotypes and an additional provisional genotype, D11. Clades B, C, D, G and H each contain multiple genotypes (B1-3, C1-2, D1-10, G1-3 and H1-2) while clades A, E and F each contain single genotype (A, E and F) respectively [17, 18]. Epidemiological findings reveal circulation of several genotypes in Africa. Genotype A has been detected in South America, parts of China and South Africa over the last 40 years [19], and recently in a 3 year old child in Nigeria West Africa [20]. The most endemic genotype circulating in Africa is B3. Studies have shown clade B to be endemic in sub-Saharan Africa [21] with B3 genotype reported in Ghana, Gambia, Nigeria, Libya and Tunisia [20, 22, 23]. The measles viruses isolated in 1983 from Yaoundé, Cameroon, were designated as B1 genotype. However, in 2001 viruses belonging to B3 genotype were found in the country. B3 genotype has been reported in the Gambia. The B3 genotype (2001) in Cameroon were related to B3.1 subgroup, whereas the Gambian (1993) isolates corresponded to B3.2 subgroup. Geographical distribution for period 1993–2001 of these two viruses shows that B3.1 is found from Sudan to Nigeria and Ghana extending to Cameroon, whereas B3.2 genotype is found in West Africa. In Nigeria and Ghana, the viruses co-circulate [3, 14]. Nucleotide sequence analysis show strains from Senegal clustered in B3.1 and B3.3 sub-genotypes. Measles virus detected in Tunisia and Libya from 2002 to 2009 belonged to genotype B3. Viruses isolated from 2002 to 2007 and 2009 were subtype B3.1. Seven of isolates during 2008 and 2009 epidemic were divergent from the B3 isolates and can represent a new subtype of genotype B3 [21]. B3 strain circulates in Addis Ababa, Bahir Dar and possibly elsewhere in Ethiopia [24]. In a 2014 outbreak among refugees from Central African Republic in Cameroon, the genotype B3 found were similar to those circulating in Northern Cameroon in 2010–2011 [25]. Clade B viruses is reported to be endemic in central and western parts of sub-Saharan Africa while genotypes D2 and D4 has been continually detected in southern and eastern parts of Africa. D10 in Uganda is represented by Clade MVi/Kampala. UGA/51.00.1 with accession number AY923185.1. Genotype C2 is found to circulate widely in northern Africa [17, 26–28].

## **2.3 MV complications in developing countries**

Measles is characterized by fever of 38°C or more; maculopapular rash of 3 days or more; with one or combination of coryza, cough, conjunctivitis and Koplik spots in the oral mucosa of measles' victims [29]. Mortality rates can exceed 10% in parts of the developing world. Sequela of measles includes giant cell pneumonia, inclusion body encephalitis and sub-acute sclerosing pan encephalitis [SSPE] [30]. A study carried out in the largest children's hospital in Ibadan-Nigeria in West Africa observed several complications ranging from bronchopneumonia (60%), heart failure (12%), gastroenteritis (11%), protein losing malnutrition (8%), encephalitis (5%), croup (2%) and dehydration (2%) [10], whereas bacterial complication is the usual cause of death when measles kills malnourished children [31].
