Mixed genotypes of Orientia tsutsugamushi in conserved genes and a single immune-dominant tsa56 genotype discovered from a patient with scrub typhus in Hainan Island, China: a case report.

BACKGROUND: Orientia tsutsugamushi (O. tsutsugamushi), an obligate intracellular bacterium, is transmitted to humans through infected larval trombiculid mite bites, causing scrub typhus. Mixed genotypes of O. tsutsugamushi in canonical conserved genes were reported in 8-25% of blood samples from patients. Yet, there are few clinical descriptions of these mixed O. tsutsugamushi-infected patients. CASE PRESENTATION: We report a patient with scrub typhus complicated with pulmonary involvement and hepatic dysfunction, who carried mixed genotypes of the conserved genes but had a single immune-dominant 56-kDa type-specific antigen (tsa56) genotype. The patient was successfully recovered by doxycycline treatment. CONCLUSIONS: In this reported case, both patient's eschar and blood samples have repeatedly shown the same results, i.e., no variants were discovered in tsa56 gene that bears multiple hypervariable regions. Whereas the selected highly conserved genes were identified with up to 32 variants in a 2700 base-pair concatenated sequence. The prevalence, disease severity and mechanism of these single-tsa56-genotype mixed infections remain to be investigated on a large scale with more cases.

Genomic bacterial load associated with bacterial genotypes and clinical characteristics in patients with scrub typhus in Hainan Island, Southern China.

Scrub typhus, caused by mite-borne Orientia tsutsugamushi (O. tsutsugamushi), is a major febrile disease in the Asia-Pacific region. The DNA load of O. tsutsugamushi in the blood was previously found to be significantly higher in patients with fatal disease than those with non-fatal disease and correlated with the duration of illness, presence of eschar, and hepatic enzyme levels. In this prospective observation study, we analyzed the association of bacterial DNA load with clinical features, disease severity, and genotype using real-time PCR targeting the 56 kDa TSA gene of O. tsutsugamushi in the blood samples of 117 surviving patients with scrub typhus who had not received appropriate antibiotic treatment. The median O. tsutsugamushi DNA load was 3.11×103 copies/mL (range, 44 to 3.3×106 copies/mL). The severity of patients was categorized as mild, moderate, and severe based on the number of dysfunctional organs, and no significant difference in O. tsutsugamushi DNA load was found among these groups. Patients infected with the Karp group showed a significantly higher O. tsutsugamushi DNA load than those in the Gilliam (P < 0.05) and TA763 (P < 0.01) groups. Patients belonging to the Li ethnic group showed a significantly higher DNA load than those in the Han ethnic groups. The blood bacterial DNA load of patients showed no significant difference between groups divided by gender, age, with or without eschar, or the season of disease onset. The highest body temperature recorded during fever onset was positively correlated with O. tsutsugamushi DNA load (ρ = 0.272, P = 0.022). Correlation analyses indicated that the serum total bilirubin level was positively correlated with O. tsutsugamushi DNA load. In conclusion, the findings in this study demonstrated the association of DNA load of O. tsutsugamushi with the severity and genotype in patients with scrub typhus in Hainan, China.

Phylogenetic Analysis of the Dengue Virus Strains Causing the 2019 Dengue Fever Outbreak in Hainan, China.

Dengue virus is an arthropod-borne pathogen that is transmitted to humans primarily by Aedes spp. mosquitos, causing the acute infectious disease, dengue fever (DF). Until 2019, no dengue outbreak had been reported in Hainan Province for over 20 years. However, in early September of 2019, an increasing number of infected cases appeared and the DF outbreak lasted for over one month in Haikou City, Hainan Province. In our study, we collected 97 plasma samples from DF patients at three hospitals, as well as 1585 mosquito larvae samples from puddles in different areas of Haikou. There were 49 (50.5%) plasma samples found to be strongly positive and 9 (9.3%) plasma samples were weakly positive against the NS1 antigen. We discovered DENV both in the patient's plasma samples and mosquito larvae samples, and isolated the virus from C6/36 cells inoculated with the acute phase serum of patients. Phylogenetic analysis revealed that the new strains were the most closely related to the epidemic strain in the southern regions of China, belonging to lineage IV, genotype I, DENV-1. Compared to the seven closest strains from neighboring countries and provinces, a total of 18 amino acid mutations occurred in the coding sequences (CDS) of the new isolated strain, DENV1 HMU-HKU-2. Our data shows that dengue virus is re-emerged in Hainan, and pose new threats for public health. Thus regular molecular epidemiological surveillance is necessary for control and prevention of DENV transmission.

Compare the epidemiological and clinical features of imported and local COVID-19 cases in Hainan, China.

BACKGROUND: Effective management of imported cases is an important part of epidemic prevention and control. Hainan Province, China reported 168 coronavirus disease 2019 (COVID-19), including 112 imported cases on February 19, 2020, but successfully contained the epidemic within 1 month. We described the epidemiological and clinical characteristics of COVID-19 in Hainan and compared these features between imported and local cases to provide information for other international epidemic areas. METHODS: We included 91 patients (56 imported and 35 local cases) from two designated hospitals for COVID-19 in Haikou, China, from January 20 to February 19, 2020. Data on the demographic, epidemiological, clinical and laboratory characteristics were extracted from medical records. Patients were followed until April 21, 2020, and the levels of antibodies at the follow-ups were also analysed by the Wilcoxon matched-pairs signed ranks test. RESULTS: Of the 91 patients, 78 (85.7%) patients were diagnosed within the first three weeks after the first case was identified (Day 1: Jan 22, 2020), while the number of local cases started to increase during the third week. No new cases occurred after Day 29. Fever and cough were two main clinical manifestations. In total, 15 (16.5%) patients were severe, 14 (15.4%) had complicated infections, nine (9.9%) were admitted to the intensive care unit, and three died. The median duration of viral shedding in feces was longer than that in nasopharyngeal swabs (19 days vs 16 days, P = 0.007). Compared with local cases, imported cases were older and had a higher incidence of fever and concurrent infections. There was no difference in outcomes between the two groups. IgG was positive in 92.8% patients (77/83) in the follow-up at week 2 after discharge, while 88.4% patients (38/43) had a reduction in IgG levels in the follow-up at week 4 after discharge, and the median level was lower than that in the follow-up at week 2 (10.95 S/Cut Off (S/CO) vs 15.02 S/CO, P <  0.001). CONCLUSION: Imported cases were more severe than local cases but had similar prognoses. The level of IgG antibodies declined from week 6 to week 8 after onset. The short epidemic period in Hainan suggests that the epidemic could be quickly brought under control if proper timely measures were taken.