Measles outbreak reveals measles susceptibility among adults in Namibia, 2009 - 2011.

BACKGROUND: The World Health Organization, African Region, set the goal of achieving measles elimination by 2020. Namibia was one of seven African countries to implement an accelerated measles control strategy beginning in 1996. Following implementation of this strategy, measles incidence decreased; however, between 2009 and 2011 a major outbreak occurred in Namibia. METHODS: Measles vaccination coverage data were analysed and a descriptive epidemiological analysis of the measles outbreak was conducted using measles case-based surveillance and laboratory data. RESULTS: During 1989 - 2008, MCV1 (the first routine dose of measles vaccine) coverage increased from 56% to 73% and five supplementary immunisation activities were implemented. During the outbreak (August 2009 - February 2011), 4 605 suspected measles cases were reported; of these, 3 256 were confirmed by laboratory testing or epidemiological linkage. Opuwo, a largely rural district in north-western Namibia with nomadic populations, had the highest confirmed measles incidence (16 427 cases per million). Infants aged ≤11 months had the highest cumulative age-specific incidence (9 252 cases per million) and comprised 22% of all confirmed cases; however, cases occurred across a wide age range, including adults aged ≥30 years. Among confirmed cases, 85% were unvaccinated or had unknown vaccination history. The predominantly detected measles virus genotype was B3, circulating in concurrent outbreaks in southern Africa, and B2, previously detected in Angola. CONCLUSION: A large-scale measles outbreak with sustained transmission over 18 months occurred in Namibia, probably caused by importation. The wide age distribution of cases indicated measles-susceptible individuals accumulated over several decades prior to the start of the outbreak.

Measles resurgence in southern Africa: challenges to measles elimination.

INTRODUCTION: In seven southern African countries (Botswana, Lesotho, Malawi, Namibia, South Africa, Swaziland and Zimbabwe), following implementation of a measles mortality reduction strategy starting in 1996, the number of annually reported measles cases decreased sharply to less than one per million population during 2006-2008. However, during 2009-2010, large outbreaks occurred in these countries. In 2011, a goal for measles elimination by 2020 was set in the World Health Organization (WHO) African Region (AFR). We reviewed the implementation of the measles control strategy and measles epidemiology during the resurgence in the seven southern African countries. METHODS: Estimated coverage with routine measles vaccination, supplemental immunization activities (SIA), annually reported measles cases by country, and measles surveillance and laboratory data were analyzed using descriptive analysis. RESULTS: In the seven countries, coverage with the routine first dose of measles-containing vaccine (MCV1) decreased from 80% to 65% during 1996-2004, then increased to 84% in 2011; during 1996-2011, 79,696,523 people were reached with measles vaccination during 45 SIAs. Annually reported measles cases decreased from 61,160 cases to 60 cases and measles incidence decreased to <1 case per million during 1996-2008. During 2009-2010, large outbreaks that included cases among older children and adults were reported in all seven countries, starting in South Africa and Namibia in mid-2009 and in the other five countries by early 2010. The measles virus genotype detected was predominantly genotype B3. CONCLUSION: The measles resurgence highlighted challenges to achieving measles elimination in AFR by 2020. To achieve this goal, high two-dose measles vaccine coverage by strengthening routine immunization systems and conducting timely SIAs targeting expanded age groups, potentially including young adults, and maintaining outbreak preparedness to rapidly respond to outbreaks will be needed.

Measles outbreak in South Africa: epidemiology of laboratory-confirmed measles cases and assessment of intervention, 2009-2011.

BACKGROUND: Since 1995, measles vaccination at nine and 18 months has been routine in South Africa; however, coverage seldom reached >95%. We describe the epidemiology of laboratory-confirmed measles case-patients and assess the impact of the nationwide mass vaccination campaign during the 2009 to 2011 measles outbreak in South Africa. METHODS: Serum specimens collected from patients with suspected-measles were tested for measles-specific IgM antibodies using an enzyme-linked immunosorbent assay and genotypes of a subset were determined. To estimate the impact of the nationwide mass vaccination campaign, we compared incidence in the seven months pre- (1 September 2009-11 April 2010) and seven months post-vaccination campaign (24 May 2010-31 December 2010) periods in seven provinces of South Africa. RESULTS: A total of 18,431 laboratory-confirmed measles case-patients were reported from all nine provinces of South Africa (cumulative incidence 37 per 100,000 population). The highest cumulative incidence per 100,000 population was in children aged <1 year (603), distributed as follows: <6 months (302/100,000), 6 to 8 months (1083/100,000) and 9 to 11 months (724/100,000). Forty eight percent of case-patients were ≥ 5 years (cumulative incidence 54/100,000). Cumulative incidence decreased with increasing age to 2/100,000 in persons ≥ 40 years. A single strain of measles virus (genotype B3) circulated throughout the outbreak. Prior to the vaccination campaign, cumulative incidence in the targeted vs. non-targeted age group was 5.9-fold higher, decreasing to 1.7 fold following the campaign (P<0.001) and an estimated 1,380 laboratory-confirmed measles case-patients were prevented. CONCLUSION: We observed a reduction in measles incidence following the nationwide mass vaccination campaign even though it was conducted approximately one year after the outbreak started. A booster dose at school entry may be of value given the high incidence in persons >5 years.

Status of global virologic surveillance for rubella viruses.

The suspected measles case definition captures rubella cases. Therefore, measles surveillance will be improved in the course of the control and eventual elimination of rubella transmission. One aspect of rubella control, virologic surveillance, is reviewed here. A systematic nomenclature for rubella viruses (RVs) based on 13 genotypes has been established and is updated when warranted by increases in information about RVs. From 2005 through 2010, the genotypes of RVs most frequently reported were 1E, 1G, and 2B, and genotypes 1a, 1B, 1C, 1h, 1j, and 2C were less frequently reported. Virologic surveillance can support rubella control and elimination. Synopses of rubella virologic surveillance in various countries, regions, and globally are given, including characterization of viruses from imported cases in a country that has eliminated rubella and studies of endemic viruses circulating in countries without rubella control objectives. Current challenges are discussed.

Possible interruption of measles virus transmission, Uganda, 2006-2009.

To determine what measles virus genotype(s) circulated in Uganda after strategic interventions aimed at controlling/eliminating measles, we examined samples obtained during 2006-2009 and found only genotype B3.1, which had not been previously detected. Kenya was the likely source, but other countries cannot be excluded.

Measles virus strain diversity, Nigeria and Democratic Republic of the Congo.

We investigated the genetic diversity of measles virus (MV) in Nigeria (2004-2005) and the Democratic Republic of the Congo (DRC) (2002-2006). Genotype B3 strains circulating in Kinshasa, DRC, in 2002-2003 were fully replaced by genotype B2 in 2004 at the end of the second Congo war. In Nigeria (2004-2005), two genetic clusters of genotype B3, both of which were most closely related to 1 variant from 1998, were identified. Longitudinal analysis of MV strain diversity in Nigeria suggested that only a few of the previously described 1997-1998 variants had continued to circulate, but this finding was concomitant with a rapid restoration of genetic diversity, probably caused by low vaccination coverage and high birth rates. In contrast, the relatively low genetic diversity of MV in DRC and the genotype replacement in Kinshasa reflect a notable improvement in local measles control.

Genetic characterization and progression of B3 measles genotype in Ethiopia: a study of five measles outbreak cases.

BACKGROUND: One of the countries where measles remains endemic is Ethiopia. Previously, sequence data from Measles Viruses (MV) circulating in Ethiopia were obtained from clinical specimens. Now the Ethiopian Health and Nutrition Research Institute (ENHRI) has implemented cell culture techniques to isolate measles virus and molecular epidemiologic studies can be generated more easily. OBJECTIVE: To characterize the strains of Measles Virus circulating in Ethiopia during measles outbreaks in 2006 using viral isolates, and compare the results to previously identified Ethiopian strains. METHODS: A case study and convenience sampling method were conducted on five measles outbreak cases tb identify the circulating measles virus genotype in Addis Ababa and Amhara regions of Ethiopia in 2006. RESULTS: Three isolates were obtained from five specimens collected in two regions (1 from Amhara: Bahir Dar, and 2 from Addis Ababa: Addis Ketema and Kolefe Keranio subcities) in Ethiopia during 2006. The viral isolates were analyzed using standard genotyping protocols and were classified as genotype B3, identical to the strain circulating widely in West Africa and imported into Europe (Britain, Netherlands, Germany) and America (Mexico, USA, Canada). CONCLUSION: The conserved sequences among three isolates, covering a 3-month period, suggest that this B3 strain was circulating in Addis Ababa, Bahir Dar and possibly elsewhere in Ethiopia. To interrupt the transmission and circulation of MV, Ethiopia needs a strong national program of epidemiological surveillance, with characterization of circulating MV performed in a timely manner.

Studies of reservoir hosts for Marburg virus.

To determine reservoir hosts for Marburg virus (MARV), we examined the fauna of a mine in northeastern Democratic Republic of the Congo. The mine was associated with a protracted outbreak of Marburg hemorrhagic fever during 1998-2000. We found MARV nucleic acid in 12 bats, comprising 3.0%-3.6% of 2 species of insectivorous bat and 1 species of fruit bat. We found antibody to the virus in the serum of 9.7% of 1 of the insectivorous species and in 20.5% of the fruit bat species, but attempts to isolate virus were unsuccessful.

Genotyping of measles virus in clinical specimens on the basis of oligonucleotide microarray hybridization patterns.

An oligonucleotide microarray hybridization method for identification of most known measles virus (MV) genotypes was developed. Like the conventional genotyping method, the microarray relied on detecting sequence differences in the 450-nucleotide region coding for the COOH-terminal 150 amino acids of the nucleoprotein (N). This region was amplified using PCR primers binding to all known MV genotypes. The microarray included 71 pairs of oligonucleotide probes (oligoprobes) immobilized on glass slides. Each pair consisted of a genotype-specific oligoprobe, which matched the sequence of only one target genotype, and a control oligoprobe, which contained mismatches at the nucleotide positions unique to this genotype. A pattern recognition algorithm based on cluster analysis of the ratios of hybridization signals from specific and control oligoprobes was used to identify the specific MV genotype. Following the initial validation, the method was used for rapid genotyping of two panels of coded samples. The results of this study showed good sensitivity (90.7%), specificity (100%), and genotype agreement (91.8%) for the new method compared to the results of genotyping conducted using phylogenetic analysis of viral sequences of the C terminus of the N gene. In addition, the microarray demonstrated the ability to identify potential new genotypes of MV based on the similarity of their hybridization patterns with those of known MV genotypes.

Marburg hemorrhagic fever associated with multiple genetic lineages of virus.

BACKGROUND: An outbreak of Marburg hemorrhagic fever was first observed in a gold-mining village in northeastern Democratic Republic of the Congo in October 1998. METHODS: We investigated the outbreak of Marburg hemorrhagic fever most intensively in May and October 1999. Sporadic cases and short chains of human-to-human transmission continued to occur until September 2000. Suspected cases were identified on the basis of a case definition; cases were confirmed by the detection of virus antigen and nucleic acid in blood, cell culture, antibody responses, and immunohistochemical analysis. RESULTS: A total of 154 cases (48 laboratory-confirmed and 106 suspected) were identified (case fatality rate, 83 percent); 52 percent of cases were in young male miners. Only 27 percent of these men reported having had contact with other affected persons, whereas 67 percent of patients who were not miners reported such contact (P<0.001). Most of the affected miners (94 percent) worked in an underground mine. Cessation of the outbreak coincided with flooding of the mine. Epidemiologic evidence of multiple introductions of infection into the population was substantiated by the detection of at least nine genetically distinct lineages of virus in circulation during the outbreak. CONCLUSIONS: Marburg hemorrhagic fever can have a very high case fatality rate. Since multiple genetic variants of virus were identified, ongoing introduction of virus into the population helped perpetuate this outbreak. The findings imply that reservoir hosts of Marburg virus inhabit caves, mines, or similar habitats.

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

This study describes two measles outbreaks--one in Cape Town, South Africa in November 2002, and the other in Luanda, Angola in March 2003. The outbreaks were notable because they were caused by closely related genotype B2 viruses. This genotype was first described in an outbreak in Libreville, Gabon in the 1980s and was labeled as inactive by the World Health Organization in 2003 because it had not been detected for over 15 years. As the first three cases in the Cape Town outbreak were Angolan citizens who recently arrived from Angola, it appears likely that the source of the virus was Angola. Molecular analysis of specimens collected during the outbreak in Luanda provided direct evidence for the circulation of genotype B2 measles virus (MV) in Angola. This study clearly demonstrates that there is still active circulation of genotype B2 in Africa, and we propose that its apparent inactivity is merely the result of insufficient virologic/molecular surveillance in the region. These findings highlight the need for expanded molecular surveillance in Africa.

Phylogenetic evidence of widespread distribution of genotype 3 JC virus in Africa and identification of a type 7 isolate in an African AIDS patient.

JC virus (JCV) is the cause of progressive multifocal leukoencephalophathy (PML) in immunocompromised patients. The paucity of reports from Africa has led to the hypothesis that PML is rare because of an absence of virus genotypes associated with the condition. Genotypes 3 and 6 have been identified in East and West Africa but the distribution of types across the rest of Africa is unknown. Full-length sequences of five JCV cerebrospinal fluid samples from PML patients in South Africa are reported here. Three isolates from African AIDS patients grouped with type 3A or 3B, and one with type 7, while one from a Caucasian leukaemia patient grouped with type 2D. Widespread distribution of type 3 on the continent may reflect migration patterns in antiquity, but this is the first report of type 7 in an African individual. Type 2D has only been isolated previously in South Asia, although transmission of this genotype to Europeans who later settled in South Africa is not unlikely.