A new species of parvovirus tentatively named human bocavirus 4 (HBoV4) was genetically characterized. Among 641 feces samples from children and adults the most commonly detected bocaviruses species were HBoV2>HBoV3>HBoV4>HBoV1 with HBoV2 prevalence of 21% and 26% in Nigerian and Tunisian children. HBoV3 and HBoV4 species combined were found in 12/192 cases of non-polio acute flaccid paralysis (AFP) from Tunisia and Nigeria and 0/96 healthy Tunisian contacts (p=0.01). Evidence of extensive recombination at the NP1 and VP1 gene boundary between and within species was found. The multiple species and high degree of genetic diversity seen among the human bocaviruses found in feces relative to the highly homogeneous HBoV1 suggest that this world-wide distributed respiratory pathogen may have recently evolved from an enteric bocavirus, perhaps after acquiring an expanded tropism favoring the respiratory track. Elucidating the possible role of the newly identified enteric bocaviruses in human diseases including AFP and diarrhea will require further epidemiological studies.

A critical component of laboratory surveillance for measles is the genetic characterization of circulating wild-type viruses. The World Health Organization (WHO) Measles and Rubella Laboratory Network (LabNet), provides for standardized testing in 183 countries and supports genetic characterization of currently circulating strains of measles viruses. The goal of this report is to describe the lessons learned from nearly 20 years of virologic surveillance for measles, to describe the global databases for measles sequences, and to provide regional updates about measles genotypes detected by recent surveillance activities. Virologic surveillance for measles is now well established in all of the WHO regions, and most countries have conducted at least some baseline surveillance. The WHO Global Genotype Database contains >7000 genotype reports, and the Measles Nucleotide Surveillance (MeaNS) contains >4000 entries. This sequence information has proven to be extremely useful for tracking global transmission patterns and for documenting the interruption of transmission in some countries. The future challenges will be to develop quality control programs for molecular methods and to continue to expand virologic surveillance activities in all regions.

Recent West Nile virus (WNV) outbreaks have occurred in the Mediterranean basin. In Algeria in 1994, about 50 human cases of WN encephalitis were suspected, including 8 fatal cases. In Morocco in 1996, 94 equines were affected of which 42 died. In Tunisia in 1997, 173 patients were hospitalized for encephalitis or meningoencephalitis. West Nile serology performed on 129 patients was positive in 111 cases (87%) including 5 fatal cases. In Italy in 1998, 14 horses located in Tuscany were laboratory confirmed for WNV infection; 6 animals died. In Israel in 1998, serum samples from horses suffering from encephalomyelitis had WNV antibodies and virus was isolated from the brain of a stork; in 1999 WNV was identified in commercial geese flocks, and in 2000 hundreds of human cases have been reported. In September 2000, WNV infection was detected in horses located in southern France, close to the Camargue National Park where a WNV outbreak occurred in 1962. By November 30, 76 cases were laboratory confirmed among 131 equines presenting with neurological disorders. No human case has been laboratory confirmed among clinically suspect patients. The virus isolated from a brain biopsy is closely related to the Morocco‐1996 and Italy‐1998 isolates from horses, to the Senegal‐1993 and Kenya‐1998 isolates from mosquitoes, and to the human isolate from Volgograd‐1999. It is distinguishable from the group including the Israel‐1998 and New York‐1999 isolates, as well as the Tunisia‐1997 human isolate.

This report is an overview of enterovirus epidemiology in Tunisia during a 12-year period from 1992 to 2003. A total of 4700 clinical samples were collected as part of the national poliovirus surveillance programme and the routine diagnostic programme for aseptic meningitis. Enterovirus detection was performed by isolation on cell culture according to World Health Organization recommended protocols. Serotype identification was performed by seroneutralization of the cytopathic effect using pools of specific antisera and sequencing in the VP1 region of the genome. Poliovirus isolates were assessed for their wild or vaccine-related origin by standard World Health Organization recommended methods (PCR, probe hybridization and ELISA). The results confirm the interruption of wild poliovirus circulation since 1995. A total of 236 non-polio enterovirus (NPEV) strains were isolated; seroneutralization allowed typing of 93 % (219 out of 236) of them. The antisera used allowed the identification of the most common enterovirus serotypes. The remaining 17 isolates were sequenced; 16 of them belonged to enterovirus serotypes that were not targeted by the antisera pools used. A total of 29 different serotypes of NPEV were detected in the country during the study period. Echoviruses of serotypes 6, 11 and 30 were the most frequently isolated, almost every year; other serotypes had a cyclic occurrence and others were detected during a limited period with very few isolates. The NPEV isolation rate varied from year to year but was steadily under 10 %, suggesting a relatively low prevalence of these viruses in comparison to that in other developing countries. A seasonal variation was also noted; the high transmission period starts in March and peaks in September-November. This study is the first report of the epidemiology of NPEV in Tunisia. These viruses are associated with various diseases and epidemiological data may help to clarify their impact on human health.

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Hepatitis B virus (HBV) is characterized by genetic heterogeneity, including genotypes and mutations. Eight genotypes (A-H) have been identified throughout the world with a characteristic geographical distribution. Previous studies also suggest that the viral genotypes may correlate with differences in clinical features of the infection. Two types of mutations were particularly described, precore and basal promoter mutations; they may play an important role in the clinical outcome of HBV infection. The aim of this study was to investigate the prevalence of HBV genotypes and HBV variants in Tunisia, and their eventual association with severity of liver disease. Using a molecular method, HBV genotypes, precore and basal core promoter mutations were determined in 56 asymptomatic carriers and in 82 patients with histologically verified chronic liver disease and hepatocellular carcinoma (HCC). Three genotypes (D, A, and E) were detected; the prevalence was 80%, 8%, and 9%, respectively. No significant difference was observed for genotype D with clinical status. HBV mutants were detected in 93% of cases, precore mutants were the most prevalent. Basal core promoter mutants were observed in 61% of cases, they were frequently characterized by a double mutation in 1762 and 1764. Co-infection by these two types of mutants was detected in 50% of cases. Genotype D was the most prevalent HBV genotype in Tunisia. High circulation of precore and basal core promoter mutants are common in chronic hepatitis B infection in Tunisia.

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BackgroundIn Tunisia, country of intermediate endemicity for Hepatitis B virus (HBV) infection, most molecular studies on the virus have been carried out in the North of the country and little is known about other regions. The aim of this study was to determine HBV genotype and subgenotypes in Central-East Tunisia. A total of 217 HBs antigen positive patients were enrolled and determination of genotype was investigated in 130 patients with detectable HBV DNA. HBV genotyping methods were: PCR-RFLP on the pre-S region, a PCR using type-specific primers in the S region (TSP-PCR) and partial sequencing in the pre-S region.ResultsThree genotypes (D, B and A) were detected by the PCR-RFLP method and two (D and A) with the TSP-PCR method, the concordance between the two methods was 93%. Sequencing and phylogenetic analysis of 32 strains, retrieved the same genotype (D and A) for samples with concordant results and genotype D for samples with discordant results. The sequences of discordant genotypes had a restriction site in the pre-S gene which led to erroneous result by the PCR-RFLP method. Thus, prevalence of genotype D and A was 96% and 4%, respectively. Phylogenetic analysis showed the predominance of two subgenotypes D1 (55%) and D7 (41%). Only one strain clustered with D3 subgenotype (3%).ConclusionsPredominance of subgenotype D7 appears to occur in northern regions of Africa with transition to subgenotype D1 in the East of the continent. HBV genetic variability may lead to wrong results in rapid genotyping methods and sequence analysis is needed to clarify atypical results.