Molecular epidemiology of measles virus in Kenya

Abstract

Measles causes significant morbidity and mortality globally. Many countries have embarked on immunization programs to control and prevent measles outbreaks and eventually to eliminate endemic measles. Kenya is currently in the outbreak control and prevention stage for measles. Measles virus genotyping is important for molecular epidemiological purposes, including the documentation of the elimination of endemic measles virus strains from a country, and mapping of transmission pathways. In this study, we collected clinical specimens from measles outbreak cases in 2002 in Kenya for measles virus genotyping. We were able to isolate and/or detect measles virus in 10 cases from 5 of the 8 provinces in Kenya. All these Kenyan measles strains were determined to be genotype D4 strains when compared to the standard World Health Organization-designated measles virus reference strains. Interestingly, the Kenyan D4 strains clustered into two distinct D4 subgroups. In addition, the inclusion of other published D4 measles strains in this analysis indicated that there are four distinct D4 clusterings, or subgroups: Montreal-like, India-like, Johannesburg-like, and Ethiopia-like. This is the first measles molecular epidemiology study in Kenya and establishes the current endemic measles strain as genotype D4. Importantly, this study shows that the Kenyan D4 strains are distinct from the B3 measles strain found in West Africa and the D4 strains reported in Ethiopia.

Serological and molecular epidemiology of measles virus outbreaks reported in Ethiopia during 2000–2004

“…The majority (36) of the strains were Ethiopian like, the strain responsible for the 2000-2004 measles outbreaks reported from most of Oromia, Tigray, SNNPR, Amhara regions, and other areas, suggesting that this D4 strain is the domestic strain in Ethiopia. Genotype D4 was also identified in other developing countries, such as India, Iran, Kenya, and South Africa [WHO, 2001;Mbugua et al, 2003;Rota and Bellini, 2003]. The sequences of the three cases that occurred in Diredawa town were South African like and the two that occurred in Addis Ababa were Sudan and India like.…”

Antigenic Drift Defines a New D4 Subgenotype of Measles Virus

“…Distinct unrelated subgroups for genotype D4 viruses were previously proposed exclusively on the basis of phylogenic analysis of the MeV-N gene (45)(46)(47). We are aware that the minimum genetic distance observed in the MeV-H genes between the proposed D4 subgenotypes (1.5%) does not match WHO criteria for assigning a new genotype (Ͼ2%), and the MeV-N minimum genetic distance (2.5%) is at best borderline (Ͼ2.5%).…”

Measles virus genotype B2 is not inactive: Evidence of continued circulation in Africa

“…In contrast, clade D viruses appear to circulate endemically in the southern and eastern parts of the African continent. Endemic circulation of genotypes D2 and D4 has been shown in South Africa, Namibia, Zimbabwe, and Kenya, while genotypes D4 and D8 have been reported from as far north as Ethiopia [Kreis et al, 1997;Nigatu et al, 2001;Mbugua et al, 2003;Rota and Bellini, 2003]. Characterization of MVs from an outbreak in Morocco in 1998/1999 showed that they were genotype C2, which suggests that Northern Africa may be linked to European transmission patterns rather than to African patterns [Alla et al, 2002].…”