Comparison of virological and serological methods for laboratory confirmation of rubella.

BACKGROUND: Work toward rubella elimination has accelerated globally. A reliable laboratory confirmation of rubella-suspected cases is required for effective surveillance in the rubella-elimination phase. The use of adequate specimens is a key to improving the quality of this surveillance. STUDY DESIGN: We conducted rubella virus (RUBV) isolation and RUBV genome or anti-RUBV IgM detection on 1023 specimens from 372 rubella- or measles-suspected cases collected through the national surveillance program in Sakai city of Osaka prefecture, Japan between 2011 and 2013. The resulting data were analyzed by specimen type, collection date, and immunological status. RESULTS: Among the three specimen types (throat swab, serum or plasma, and urine) collected through 10 days post-rash onset, the highest success rates for RUBV genome detection and RUBV isolation were obtained using throat swabs. In agreement with previous work, RUBV-specific IgM were undetectable in 50% of the rubella-confirmed cases until 3 days after rash onset. The success rates of RUBV genome detection and RUBV isolation declined in association with the appearance of RUBV-specific antibodies in blood, especially in serum, plasma, or urine samples. CONCLUSION: Throat swabs are the most optimal specimen types for both RUBV genome detection and RUBV isolation; serum/plasma samples may be suboptimal, especially for RUBV isolation. The findings from this study will provide useful information for improving laboratory surveillance for rubella in the elimination phase.

Clinical value of enzyme immunoassay that detects rubella-specific immunoglobulin M immediately after disease onset.

A total of 300 patients with nucleic acid test-confirmed rubella, mostly adults, were investigated to determine the clinical value of a rubella-specific IgM test using an EIA kit. IgM titers increased after rash onset, the median IgM titer being significantly higher 3 days post-onset than on previous days (P < 0.0001). Similarly, the IgM-positive rate at 3 days post-onset (61.5%) was significantly higher than on previous days (P < 0.0001). This IgM test against rubella at 3 days or more post-disease onset provides the clinically relevant information.

Long-term viral shedding and viral genome mutation in norovirus infection.

The duration of viral shedding in the patients from two outbreaks and four sporadic cases of norovirus (NoV) infections was investigated. The longest period of viral shedding into feces was for 173 days in an inpatient from one case of outbreak. The VP1 sequence from two long-term viral shedding cases in the outbreak revealed four synonymous and one non-synonymous mutations in one inpatient at 26 days from the onset of illness, and nine synonymous and two non-synonymous mutations and a deletion, 10 synonymous mutations and a deletion in other inpatient at 29 days and 54 days from the onset of illness, respectively. Ten of the 11 amino acid positions detected in these two inpatients were in the outermost P2 domain of the viral capsid protein, and mutations at positions 295, 297, and 394 were shared in the inpatients. Mutations in the P2 domain were in epitopes A and D or near epitopes A, C, and E, suggesting that the long-term carrier state of norovirus infection contributes to the generation of escape mutants by host immunoselection.

An outbreak of cryptosporidiosis suspected to be related to contaminated food, October 2006, Sakai City, Japan.

On October 17, 2006, the Sakai City Public Health Center received a report of acute gastroenteritis among 4 members from the same company who had eaten raw meat dish called "Yukke: Korean-style beef tartar" and raw liver at a rotisserie in Sakai City on October 7. Based on information from interviews, the median incubation period was 5.5 (range, 5-7 days), and the median length of illness was 7 days (range, 4-10 days). The illness was characterized by a prolonged incubation period, non-bloody watery diarrhea, reduced vomiting, and light fever, which led us to suspect an enteric protozoan infection. Stool specimens obtained from 3 of the 4 symptomatic patients were positive for Cryptosporidium oocysts. They, along with 2 food workers, were negative for food poisoning bacteria or Norovirus. Genotyping of the Cryptosporidium isolates by direct sequencing of PCR products revealed that all the isolates were the C. parvum genotype II (bovine) and the subgenotype of IIa with 100 % homology with respective 18S rRNA and Cpgp40/15 genes. Positive implementation of tests for enteric protozoa including Cryptosporidium is necessary in the differential diagnosis of suspected foodborne gastroenteritis, particularly when it is characterized by a prolonged incubation period and severe watery diarrhea. In fact, we were able to diagnose the illness as cryptosporidiosis without waiting for the results of bacteriological and virological examinations, and thus prevented the possible occurrence of a secondary infection through an ill patient who works as cooking personnel in the company.

Combined genogroup I and II norovirus infection at a nursery.

From November 2004 to April 2005, 5 cases of norovirus (NoV) occurred in Sakai City, Japan. These were all diffuse outbreaks due to infections with genogroup II genotype 4 (GII/4) virus strains. Similar outbreaks occurred throughout Japan; hence, GII/4 was assumed to be the prevalent NoV type. However, a NoV outbreak that occurred at a nursery in May 2005, was caused by infections with GI/4 and GII/6 viruses, respectively, from different children. The time course of newly infected patients showed that this nursery outbreak had a two-peak pattern, with the peak numbers of patients occurring on May 19 and May 22. Virological examination and epidemiological research could not determine whether the GI and GII NoV infections occurred at the same time, or whether there was a time difference in their appearance in the nursery. From this outbreak, it is clear that the timing of obtaining samples and obtaining the minimal necessary number of primary samples are essential for accurate epidemiological information to be obtained. In addition, we detected genotypes that were different from the previously prevalent genotypes, which raises the possibility of more frequent NoV infection or a change in the prevalent NoV genotype in this setting. In conclusion, it is difficult to predict outbreaks of NoV; however, through vigilant and early collection and analysis of later samples throughout an outbreak, it is possible to understand the prevalence and perhaps trace the source of NoV infections.

Novel recombinant sapovirus.

We determined the complete genome sequences of two sapovirus strains isolated in Thailand and Japan. One of these strains represented a novel, naturally occurring recombinant sapovirus. Evidence suggested the recombination site was at the polymerase-capsid junction within open reading frame one.

[Newly developed Norwalk-like viruses detection ELISA by combination with monoclonal antibodies and hyperimmune rabbit sera].

Norwalk-like viruses(NLVs) antigen detection ELISA was newly developed. It is constructed with monoclonal antibodies(MAbs) as a capture antibodies and hyperimmune rabbit sera as a detector antibodies. The two MAbs reacted broadly and specifically with genogroup I and genogroup II NLVs, respectively. Total detection time is less than 3 hours and at least 90 stool samples could be tested at one time. The concordance rate with ELISA and RT-PCR was 69% and it could be raised to 71% if capsid primer sets were used. Epidemiological study revealed that among 664 normal persons one sample(0.2%) was confirmed positive by both ELISA and RT-PCR, suggested that NLV carrier may exist in the normal person. The ELISA kit has advantages such as rapid, simple and multi samples detection, and useful for the first screening test. Also it is big tool for epidemiological surveillance of NLVs invasions.