Dengue epidemiological trend in Oman: a 13-year national surveillance and strategic proposition of imported cases.

Dengue fever has emerged as a major public health problem globally in the past three decades. A 13-year national surveillance data analysis was done to describe the epidemiology and its trend of dengue disease in Oman reported between 2001 and 2013. Laboratory-confirmed dengue virus infections reported were studied retrospectively during the study period. A total of 64 laboratory confirmed cases were reported. All the patients contracted the disease during their visit to South-East Asian countries, hence classified as imported cases. The majority of the cases were reported in the year 2012 (23.4%). The most important clinical characteristics were fever (90.6%), myalgia (35.9%) and rash/petechial rash (20.3%). Thrombocytopenia was seen in 31.2% of the study subjects. The mortality was nearly 4.6% and all other patients made a full recovery. The most effective measure for travellers is taking precautions to avoid mosquito bites.

Progress toward elimination of hepatitis B virus transmission in Oman: impact of hepatitis B vaccination.

Approximately 2-7% of the Omani population has chronic hepatitis B virus (HBV) infection. To decrease this burden, universal childhood hepatitis B vaccination was introduced in Oman in 1990. The hepatitis B vaccination strategy and reported coverage were reviewed. To assess the impact of the program on chronic HBV seroprevalence, a nationally representative seroprevalence study was conducted in Oman in 2005. Since 1991, hepatitis B vaccination in Oman has reached almost every eligible child, with reported coverage of ≥ 97% for the birth dose and ≥ 94% for three doses. Of 175 children born pre-vaccine introduction, 16 (9.1%) had evidence of HBV exposure, and 4 (2.3%) had evidence of chronic infection. Of 1,890 children born after vaccine introduction, 43 (2.3%) had evidence of HBV exposure, and 10 (0.5%) had evidence of chronic infection. Oman has a strong infant hepatitis B vaccination program, resulting in a dramatic decrease in chronic HBV seroprevalence.

Epidemiology of invasive pneumococcal infection among hospitalized children aged less than 5 years in Oman.

The objective of this study was to describe the epidemiology of invasive pneumococcal disease (IPD) in Omani children. We retrospectively reviewed cases admitted in children <5 years of age who were admitted in one of 4 tertiary care facilities within the Muscat Governorate. These cases represented nearly 95% of all IPD admissions recorded throughout the country from 1 January 2006 to 31 December 2006. Cases of IPD were identified using the ICD-10 discharge code. Case definition required microbiological confirmation (i.e., isolation of Streptococcus pneumoniae from blood, cerebrospinal fluid or any other normally sterile biological fluid) or clinical diagnosis in the absence of a specimen. A total of 41 cases of IPD were identified. The annual incidence of IPD was 26.1 per 100,000 in children <2 years old and 18.6 per 100,000 in children <5 years old. Among the reported IPD cases, 22 (54%) isolates were resistant to at least one antibiotic and 15 (37%) of patients had a known comorbid medical condition. These results demonstrate that the incidence of IPD in Oman during 2006 was high compared to many of the neighboring countries and provides baseline data on the incidence of IPD in an era before the introduction of the pneumococcal conjugate vaccine (PCV). In light of evidence for a significant incidence of IPD, we recommended that a nationwide surveillance system be put in place to monitor the incidence of IPD in children <5 years of age in Oman and to document the impact of PCV.

Standardization and international multicenter validation of a PulseNet pulsed-field gel electrophoresis protocol for subtyping Shigella flexneri isolates.

Shigella flexneri is one of the agents most frequently linked to diarrheal illness in developing countries and often causes outbreaks in settings with poor hygiene or sanitary conditions. Travel is one of the means by which S. flexneri can be imported into developed countries, where this pathogen is not commonly seen. A robust and discriminatory subtyping method is needed for the surveillance of S. flexneri locally and regionally, and to aid in the detection and investigation of outbreaks. The PulseNet International network utilizes standardized pulsed-field gel electrophoresis (PFGE) protocols to carry out laboratory-based surveillance of foodborne pathogens in combination with epidemiologic data. A multicenter validation was carried out in nine PulseNet laboratories located in North and South America, Europe, and Asia, and it demonstrated that a new protocol is highly robust and reproducible for subtyping of S. flexneri. This protocol, already approved for PulseNet laboratories, applies NotI and XbaI as primary and secondary restriction enzymes, respectively, under electrophoresis conditions of initial switch time of 5 s to final switch time of 35 s, at 6 volts/cm.

Global distribution of measles genotypes and measles molecular epidemiology.

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.

Molecular characterization of rotavirus strains circulating in Oman in 2005.

Limited genotyping data are available for rotavirus strains in the Middle East. In this study, we investigated the molecular epidemiology of human rotavirus strains circulating in the Sultanate of Oman during 2005. Rotavirus was detected in 178 (57.4%) of 310 of the diarrheal stools of young children <5 years admitted to hospitals and outpatients clinics. Polyacrylamide gel electrophoresis demonstrated the cocirculation of 8 strains, although 2 strains predominated across the Sultanate. Genotyping revealed the presence of human rotavirus strains of types G1P[8], G2P[4], and G3P[8]. Several strains exhibited unusual combinations of G and P genotypes and RNA electropherotypes, indicating the likelihood of natural reassortment events occurring with a high frequency. In addition, the unusual P[10] genotype was identified among the rotavirus strains, in combination with the G1 type.

Cytogenetic studies in couples with recurrent miscarriage in the Sultanate of Oman.

Miscarriage, defined as spontaneous pregnancy loss at <20-28 weeks' gestation, is a common clinical problem. Balanced chromosomal rearrangements in either parent are an important cause of repeated pregnancy loss, particularly in the first trimester. In this study, chromosomal abnormalities that cause recurrent miscarriage were evaluated in Omani parents and some of their dysmorphic children. A total of 380 couples (760 individuals) with two or more recurrent miscarriages were examined for chromosomal aberrations during the period 1999-2006. For each proband the chromosomal preparations were analysed and karyotyped after applying a Giemsa-trypsin banding method. The overall incidence of chromosomal anomaly was 26 out of 760 individuals (3.42%). These abnormalities included 21 (2.8%) structural aberrations and 5 (0.7%) numerical anomalies. In addition to these abnormalities, 39 (5.1%) chromosomal variants were also found. The nature of these abnormalities and their relation to obstetric history are discussed. In conclusion, chromosomal abnormality is one of the causes of recurrent miscarriage. This study illustrates the incidence and distribution of chromosomal abnormalities among Omani couples with recurrent miscarriage. Cytogenetic findings could provide valuable information for genetic counselling and allow monitoring of future pregnancies by prenatal diagnosis in couples with a history of recurrent miscarriage.

Clinical relevance of nontuberculous Mycobacteria, Oman.

Little is known about the clinical relevance of nontuberculous mycobacteria (NTM) in the Arabian Peninsula. We assessed the prevalence and studied a random sample of isolates at a reference laboratory in Muscat, Oman. NTM cause disease in this region, and their prevalence has increased.

Clinical characteristics of childhood guillain-barré syndrome.

OBJECTIVES: To find the incidence, clinical pattern and outcome of Guillain-Barre syndrome in the Sultanate of Oman in children less than 15 years of age. METHODS: All children under fifteen years with acute flaccid paralysis were admitted to identify the underlying cause. The diagnosis of Gullain Barre syndrome was made by clinical criteria, cerebrospinal fluid findings and nerve conduction studies. Intravenous immunoglobulins were given to all and two needed plasmapharesis. RESULTS: Sixty-one children were diagnosed as Guillan-Barré syndrome and constituted 20% of cases of acute flaccid paralysis. Males 39 (63.9%) outnumbered females (36.1%).The annual incidence below 15 years was 0.45/100,000. Cranial nerves were involved in 31 (50.8%) children. Albumino-cytological dissociation in cerebrospinal fluid was seen in 42/45(93.3%) cases. Acute relapse was seen in six (9.8%) cases. Eleven children (18.3%) needed ventilation. Complete recovery was seen in 45 to 310 days (mean 69.1 days). Three children (4.9%) were left with minimal residual deficit. There was no mortality. CONCLUSIONS: Guillain Barre syndrome is a serious disease, although recovery is the rule in children. The disease is associated with very low mortality and long term morbidity. Immunoglobulins have reduced the duration of hospital stay and the total time needed for recovery.

Molecular identification of 13 new enterovirus types, EV79-88, EV97, and EV100-101, members of the species Human Enterovirus B.

Molecular methods have enabled the rapid identification of new enterovirus (EV) serotypes that are untypeable using existing neutralizing antisera. As a result, sequencing of the VP1 capsid gene has been developed as a surrogate for antigenic typing to distinguish enterovirus types. In this study, 17 enterovirus isolates from four countries were identified as members of 13 new types within the species Human Enterovirus B (HEV-B) by complete genome sequencing. Members of each of these new types are at least 75% identical to one another (91% amino acid identity) in VP1, but members of different types differ from one another and from other enteroviruses by at least 27% in nucleotide sequence (26% amino acid sequence difference). The complete P1 (capsid) sequences of the new types are at least 17% different from those of all other enterovirus serotypes (14.5% amino acid sequence difference), but they are highly conserved within a type (<8% amino acid sequence difference). For both VP1 and P1, the 17 isolates are monophyletic by type with respect to all other EV serotypes. The P2 and P3 sequences are closely related to those of other HEV-B viruses (>93% amino acid identity), confirming that the 17 new strains belong to HEV-B. We propose that these 17 isolates be classified as members of 13 new human enterovirus types, enteroviruses 79-88, 97, and 100-101.

Incidence of chromosome abnormalities in the Sultanate of Oman.

OBJECTIVES: To evaluate the cytogenetic findings in Omani children referred for suspected chromosomal anomalies that caused a variety of clinical disorders. Secondly, to study the frequency of chromosomal abnormalities in these patients and to compare our results with those reported elsewhere. METHODS: We performed chromosomal analysis on 1800 consecutive pediatric patients referred to the Cytogenetics section between June 1999 and May 2004 at Central Public Health Laboratories, Sultanate of Oman. Indication for referrals for exclusion of chromosomal rearrangements was multiple congenital anomalies, dysmorphic features, unclassified mental retardation, developmental delay, growth, and endocrine disorders. We carried out the lymphocyte culture according to standard methods. RESULTS: We found various types of chromosomal anomalies in 510 (28.3%) children and showed abnormal karyotypes in the form of trisomy 21 (391; 21.7%), trisomy 18 (32; 1.8%), trisomy 13 (20; 1.1%), sex chromosome aberrations (50; 2.8%) and other types of abnormalities (17; 0.95%). There was a considerable phenotypic-cytogenetic heterogeneity. We found a high rate of chromosomal abnormalities in the present study, and we observed variations in the frequency of chromosomal aberrations reported by different investigators. CONCLUSION: The higher incidence of the chromosomal abnormalities demonstrates the importance of cytogenetic evaluation in patients with dysmorphic features and congenital anomalies. Our findings suggest that chromosome analysis is a useful tool in the investigation of children with genetic disorders of unknown origin for confirmation of clinical diagnosis and proper medical care followed by genetic counseling and management.

Molecular identification and characterization of two proposed new enterovirus serotypes, EV74 and EV75.

Sequencing of the gene that encodes the capsid protein VP1 has been used as a surrogate for antigenic typing in order to distinguish enterovirus serotypes; three new serotypes were identified recently by this method. In this study, 14 enterovirus isolates from six countries were characterized as members of two new types within the species Human enterovirus B, based on sequencing of the complete capsid-encoding (P1) region. Isolates within each of these two types differed significantly from one another and from all other known enterovirus serotypes on the basis of sequences that encode either VP1 alone or the entire P1 region. Members of each type were > or =77.2 % identical to one another (89.5 % amino acid identity) in VP1, but members of the two different types differed from one another and from other enteroviruses by > or =31 % in nucleotide sequence (25 % amino acid sequence difference), indicating that the two groups represent separate new candidate enterovirus types. The complete P1 sequences differed from those of all other enterovirus serotypes by > or =31 % (26 % amino acid sequence difference), but were highly conserved within a serotype (<8 % amino acid sequence difference). Phylogenetic analyses demonstrated that isolates of the same serotype were monophyletic in both VP1 and the capsid as a whole, as shown previously for other enterovirus serotypes. This paper proposes that these 14 isolates should be classified as members of two new human enterovirus types, enteroviruses 74 and 75 (EV74 and EV75).

Molecular identification of new picornaviruses and characterization of a proposed enterovirus 73 serotype.

Enteroviruses (EV) have traditionally been identified by using serotype-specific antisera in a virus-neutralization test. Three EV strains isolated in California, USA, in 1955, 1964 and 1978, and a 1995 Oman isolate, were found to be antigenically related to one another; however, the strains were not neutralized by standard EV typing antisera, suggesting that they may represent a new EV serotype. The isolates were characterized genetically by RT-PCR coupled with amplicon sequencing and comparison to a database of enterovirus nucleotide sequences. The strains were 75.3 to 87.2% identical to one another in complete VP1 nucleotide sequence, but no more than 68% identical in sequence to the prototype strain of any EV serotype. Their complete capsid sequences were closely related to one another, but only distantly related to those of any EV prototype strain. The California and Oman isolates were most closely related to members of EV cluster B, suggesting that they are unclassified members (i.e. a new serotype) of cluster B. The complete genome sequence was determined for one isolate, CA55-1988, and the predicted polyprotein sequence was 86.5 to 89.2% identical to those of other cluster B EV and 56.7 to 61.9% identical to the polyprotein sequences of EV belonging to other clusters. Isolation of this new EV serotype from samples obtained on two continents and over a period of 40 years suggests continued circulation over a wide geographical area. In keeping with standard picornavirus nomenclature, we propose that this new serotype be named 'enterovirus 73' (EV73).