Simple continuous-variable quantum key distribution scheme using a Sagnac-based Gaussian modulator.

Continuous-variable quantum key distribution (CV-QKD) is a protocol that uses quantum mechanics to ensure that the distribution of an encryption key is secure even in the presence of eavesdroppers. The wide application of CV-QKD requires low cost, system simplicity, and system stability. However, owing to the particularity of Gaussian modulation in CV-QKD, an amplitude modulator (AM) and a bias controller are required, making the system structure complex and unstable. In this Letter, we achieve two-dimensional Gaussian modulation with only one phase modulator (PM) and a Sagnac ring structure, which significantly reduces the complexity of the system. We test the Gaussian modulation stability for 10 h, and the result shows that the expected secure key rate can be maintained at 80 kbit/s under a transmission distance of 50 km. This scheme opens up new, to the best of our knowledge, possibilities for a new generation of highly stable and simple CV-QKD systems.

Caveolin-1 promotes cancer progression via inhibiting ferroptosis in head and neck squamous cell carcinoma.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) is an aggressive disease worldwide. Much progress has been made in exploring mechanisms and improving the therapy of HNSCC, but only a few studies have focused on the role of ferroptosis on HNSCC progression. The current study aimed to reveal the underlining mechanisms that caveolin-1 (CAV1)-ROS (reactive oxygen species)-ferroptosis axis affect the process of HNSCC and discover novo therapeutic targets or strategies. METHODS: The role of CAV1 in ferroptosis was analyzed by FerrDb, and its clinical significance was examined by TCGA dataset of HNSCC. The expressions of caveolin-1 (CAV1) in HNSCC tissues were measured by immunohistochemistry, western blot, and real-time PCR assay. Three siRNA sequences were designed to silence CAV1 mRNA in HNSCC cells. Cell proliferation, colony formation, wound-healing, and transwell assays were used to examine the proliferation, migration, and invasion of cancer cells. ROS evaluation and intracellular Fe2+ content assays were performed to examine the levels of ferroptosis. RESULTS: Through the analysis with published data, CAV1 was found to overexpress in HNSCC than normal tissues, and was one of the vital suppressors of ferroptosis pathway. Our study showed that CAV1 was over expressed in HNSCC tissues and the high level of CAV1 predicted poorer prognosis. Further experiments indicated that CAV1 could inhibit the ferroptosis of cancer cells and promote the proliferation, migration and invasion. CONCLUSIONS: Overexpression of CAV1 in HNSCC inhibited the process of ferroptosis, leading to aggressive phenotypes, as well as worse prognosis. The regulatory pathway of CAV1 and ferroptosis are potential targets for designing diagnostic and combined therapeutic strategies for HNSCC patients.

Practical continuous-variable quantum key distribution without finite sampling bandwidth effects.

In a practical continuous-variable quantum key distribution system, finite sampling bandwidth of the employed analog-to-digital converter at the receiver's side may lead to inaccurate results of pulse peak sampling. Then, errors in the parameters estimation resulted. Subsequently, the system performance decreases and security loopholes are exposed to eavesdroppers. In this paper, we propose a novel data acquisition scheme which consists of two parts, i.e., a dynamic delay adjusting module and a statistical power feedback-control algorithm. The proposed scheme may improve dramatically the data acquisition precision of pulse peak sampling and remove the finite sampling bandwidth effects. Moreover, the optimal peak sampling position of a pulse signal can be dynamically calibrated through monitoring the change of the statistical power of the sampled data in the proposed scheme. This helps to resist against some practical attacks, such as the well-known local oscillator calibration attack.

Field demonstration of a continuous-variable quantum key distribution network.

We report on what we believe is the first field implementation of a continuous-variable quantum key distribution (CV-QKD) network with point-to-point configuration. Four QKD nodes are deployed on standard communication infrastructures connected with commercial telecom optical fiber. Reliable key exchange is achieved in the wavelength-division-multiplexing CV-QKD network. The impact of a complex and volatile field environment on the excess noise is investigated, since excess noise controlling and reduction is arguably the major issue pertaining to distance and the secure key rate. We confirm the applicability and verify the maturity of the CV-QKD network in a metropolitan area, thus paving the way for a next-generation global secure communication network.

Metastatic parotid gland malignancy: A preliminary study in an eastern Chinese population.

OBJECTIVE: This study aimed to determine the incidence and clinicopathological patterns of metastatic carcinoma of the parotid gland. METHOD: Ninety patients with parotid gland metastases admitted to our hospital between January 2003 and December 2018 were included in this study. Clinical and pathological data were obtained from the medical records and follow-ups. Kaplan-Meier analysis was used to assess overall survival of patients. RESULTS: Among the 90 patients, parotid gland metastases originated from the head and neck in 86 (95.6%), from non-head and neck in 4 (4.4%), from the oral cavity in 30(33.3%), and from the eyelid in 21 (23.3%). Among the 85 cases with parotid gland lymph node metastasis, 45 (52.9%) were diagnosed with extra-lymph node metastasis. The capsule of the parotid lymph nodes was thinner than that of the cervical lymph nodes (P < 0.05). Hematogenous metastases to the parotid gland (only five cases) were rare, mainly from the non-head and neck malignancies. Patients with oral squamous cell carcinoma and meibomian adenocarcinoma with parotid metastatic disease had poorer overall survival (P < 0.05). CONCLUSION: Eastern China population analysis showed that parotid gland metastases usually arise from oral squamous cell carcinoma and eyelid, but rarely from cutaneous squamous cell carcinoma. Most cases metastasize to the parotid lymph nodes via the lymphatic system and are prone to extranodal extension with little or no facial nerve involvement. These findings have important implications for the treatment of metastatic parotid malignancies.

Clinical study on the pattern of lower-level lymphatic metastasis in primary tongue squamous cell carcinoma.

OBJECTIVES: To study and analyze the clinical patterns of lower-level lymph node (Ⅳ and Ⅴ) metastasis in primary tongue squamous cell carcinoma, and establish a reference for the decision-making of the lower-level neck dissection in tongue squamous cell carcinoma. METHODS: A total of 203 patients with primary tongue squamous cell carcinoma were recruited. These patients underwent simultaneous/secondary comprehensive neck (level Ⅰ-Ⅴ) dissection in Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from January 2010 to December 2015. Their clinicopathological and follow-up data were obtained and analyzed to reveal the prognosis and risk factors of primary tongue squamous cell carcinoma with lower-level lymph node metastasis. RESULTS: Among the 203 patients, the metastasis rates of levels Ⅳ and Ⅴ are 14.78% and 4.93%, respectively. Level Ⅳ metastasis is more prevalent in males than females (P=0.04); non-smokers are more likely to have level Ⅴ metastasis than smokers (P=0.046). Lymph node status in levels Ⅲ and Ⅳ are significantly associated with the risk of metastasis in level Ⅴ (P=0.001). Patients with extracapsular invasion in level Ⅲ have a significantly increased risk of metastasis in levels Ⅳ (P=0.014) and Ⅴ (P=0.026). The 5-year survival rate of patients with lower lymph node (Ⅳ/Ⅴ) metastasis is only 14.70%, which is an independent poor prognostic factor for patients with primary tongue squamous cell carcinoma (P<0.000 1). CONCLUSIONS: Most primary tongue squamous cell carcinoma metastases occur in levels Ⅰ-Ⅲ. However, the rate of lower-level lymph node metastasis is rather low. For the cN0 and cN+ patients with levels Ⅰ-Ⅱ lymph node metastases without extracapsular invasion, the strategy for level Ⅴ management may be observation rather than dissection.

HIF-1α induced NID1 expression promotes pulmonary metastases via the PI3K-AKT pathway in salivary gland adenoid cystic carcinoma.

BACKGROUND: This study aimed to investigate the potential role of nidogen 1 (NID1), a basement membrane component, in the growth and metastasis of salivary gland adenoid cystic carcinoma (SACC) and the underlying molecular mechanism. METHODS: High-throughput next-generation sequencing was used to compare the gene expression profiles of SACC with and without lung metastasis. Luciferase gene reporter assays were used to measure the NID1 promoter activity. BALB/c nude mice were used to establish a lung metastasis model of SACC to evaluate the prometastatic activity of NID1. ChIP and dual-luciferase reporter assays were performed to confirm the HIF-1α-binding site in the NID1 promoter. RESULTS: NID1 expression in SACC was significantly increased and associated with lung metastasis (P = 0.011). The elevated NID1 expression was a predictor of poor outcomes in patients with SACC (P < 0.05). Overexpression of NID1 promoted cancer cell migration and invasion through PI3K/AKT pathway activation and subsequent epithelial-mesenchymal transition (EMT), as indicated by the upregulation of N-cadherin and vimentin. Furthermore, in vivo live monitoring of a mouse model of lung cancer demonstrated the pro-metastatic role of NID1 in SACC cell lung metastasis. Hypoxia-inducible factor 1α (HIF-1α) upregulation via transfection of an HIF-1α-overexpressing plasmid enhanced HIF-1α binding to the NID1 promoter and the subsequent transcriptional activity and expression of NID1. CONCLUSION: HIF-1α-activated NID1 overexpression promotes SACC cell metastasis via PI3K/AKT pathway activation and EMT. Thus, NID1 could be a novel biomarker and therapeutic target for preventing metastasis and treating patients with SACC in future.

CD73 in small extracellular vesicles derived from HNSCC defines tumour-associated immunosuppression mediated by macrophages in the microenvironment.

Research on tumour cell-derived small extracellular vesicles (sEVs) that regulate tumour microenvironment (TME) has provided strategies for targeted therapy of head and neck squamous cell carcinoma (HNSCC). Herein, we demonstrated that sEVs derived from HNSCC cancer cells carried CD73 (sEVsCD73 ), which promoted malignant progression and mediated immune evasion. The sEVsCD73 phagocytosed by tumour-associated macrophages (TAMs) in the TME induced immunosuppression. Higher CD73high TAMs infiltration levels in the HNSCC microenvironment were correlated with poorer prognosis, while sEVsCD73 activated the NF-κB pathway in TAMs, thereby inhibiting immune function by increasing cytokines secretion such as IL-6, IL-10, TNF-α, and TGF-ß1. The absence of sEVsCD73 enhanced the sensitivity of anti-PD-1 therapy through reversed immunosuppression. Moreover, circulating sEVsCD73 increased the risk of lymph node metastasis and worse prognosis. Taken together, our study suggests that sEVsCD73 derived from tumour cells contributes to immunosuppression and is a potential predictor of anti-PD-1 responses for immune checkpoint therapy in HNSCC.

Influence of seed coating with copper, iron and zinc nanoparticles on growth and yield of tomato.

Neutral nanoparticles (NPs) of copper (Cu), iron (Fe) and zinc (Zn) are widely used in agriculture. Polymer seed coating with different metal NPs may supply important nutrients during plant growth and consequently enhances yields. In this research, three kinds of metal NPs were conducted to optimize the optimal concentration through seed coating for improving plant growth and productivity of tomato. Seeds of Venice tomato cultivars were coated by polymer-based mixture with different concentrations of Cu, Fe and Zn NPs, respectively. At harvest, seed germination, internode length, average weight of single fruit, yield and fruit shape index were measured. When compared with control, the internode length increased by 7.3% and 6.8% with low concentration of Fe NPs and Zn NPs, respectively. The average weight per fruit improved over control by 10.2% and 7.5% with low concentration of Cu NPs and Fe NPs, respectively. The yield with low concentration of Cu NPs and Fe NPs increased the yield by 10.7% and 6.5% compared with control. These results indicated that polymer seed coating with low concentration of metal NPs may promote the uptake of some nutrient and thus improve the productivity of tomato.

Tomato response to metal nanoparticles introduction into the nutrient medium.

This study is aimed to explore the capacity of metal nanoparticles (NPs) iron, zinc, copper and their combinations introduced in the Murashige-Skoog (MS) nutrient medium (NM) to affect the growth and development of tomato plants (Solanum lycopersicum L.). NPs were prepared by a flow-levitation method. Metal NPs were characterised by transmission and scanning electron microscopy, X-ray phase analysis. Average NPs diameters were: iron - 27.0 nm, zinc - 54.0 nm, copper - 79.0 nm. MS NM was modified by substitution of common metal sulphates by neutral metal NPs instead of salts. Tomato seedlings cultivation on NM MS with NPs instead of salts assures improved seedling parameters (root length and root activity) in comparison with plants grown on standard MS. Venice cultivar tomato seedlings grown on NM with metal NPs demonstrated an increase in: seed germination by 10-180%, root length by 10-20%, and root activity by 10 -125%. After 45 days of cultivation, tomato seedlings were transplanted in a greenhouse and were grown up to the harvest. Effects in seed germination and increase of crop mass depended on metal nature and NPs concentration.

Epigenetic repression of miR-17 contributed to di(2-ethylhexyl) phthalate-triggered insulin resistance by targeting Keap1-Nrf2/miR-200a axis in skeletal muscle.

Rationale: Skeletal muscle insulin resistance is detectable before type 2 diabetes is diagnosed. Exposure to di(2-ethylhexyl) phthalate (DEHP), a typical environmental endocrine-disrupting chemical, is a novel risk factor for insulin resistance and type 2 diabetes. This study aimed to explore insulin signaling regulatory pathway in skeletal muscle of the DEHP-induced insulin-resistant mice and to investigate potential therapeutic strategies for treating insulin resistance. Methods: C57BL/6J male mice were exposed to 2 mg/kg/day DEHP for 15 weeks. Whole-body glucose homeostasis, oxidative stress and deregulated miRNA-mediated molecular transduction in skeletal muscle were examined. microRNA (miRNA) interventions based on lentiviruses and adeno-associated viruses 9 (AAV9) were performed. Results: Dnmt3a-dependent promoter methylation and lncRNA Malat1-related sponge functions cooperatively downregulated miR-17 in DEHP-exposed skeletal muscle cells. DEHP suppressed miR-17 to disrupt the Keap1-Nrf2 redox system and to activate oxidative stress-responsive Txnip in skeletal muscle. Oxidative stress upregulated miR-200a, which directly targets the 3'UTR of Insr and Irs1, leading to hindered insulin signaling and impaired insulin-dependent glucose uptake in skeletal muscle, ultimately promoting the development of insulin resistance. AAV9-induced overexpression of miR-17 and lentivirus-mediated silencing of miR-200a in skeletal muscle ameliorated whole-body insulin resistance in DEHP-exposed mice. Conclusions: The miR-17/Keap1-Nrf2/miR-200a axis contributed to DEHP-induced insulin resistance. miR-17 is a positive regulator, whereas miR-200a is a negative regulator of insulin signaling in skeletal muscle, and both miRNAs have the potential to become therapeutic targets for preventing and treating insulin resistance or type 2 diabetes.

New insights into the cellular responses to iron nanoparticles in Capsicum annuum.

In this study, the anatomical and ultrastructural responses of Capsicum annuum to iron nanoparticles (Fe NPs) were determined. The results showed that the bio-effects of Fe NPs on plants could be positive or negative, depending on the additive concentrations. Low concentrations of Fe NPs were found to promote plant growth. Light and electron microscope analyses showed that the Fe NPs promoted plant growth by altering the leaf organization, and increasing the chloroplast number and grana stacking, as well as regulating the development of vascular bundles. Meanwhile, it was found that the Fe NPs could be absorbed in the roots, and then transported to the central cylinder in bio-available forms, where they were translocated and utilized by the leaves and stems. In contrast, high concentrations of Fe NPs appeared to be harmful to the plants, and the majority of Fe NPs were aggregated into cell walls and transported via the apoplastic pathway in the roots, which may potentially block the transfer of iron nutrients. Taken together, the aforementioned data showed that the rational use of Fe NPs could alleviate iron deficiency, and Fe NPs could be an ideal supply for Fe2+ ions fertilizers in agriculture.

Prolonged air leak after video-assisted thoracic surgery lung cancer resection: risk factors and its effect on postoperative clinical recovery.

BACKGROUND: Prolonged air leak (PAL) is one of the most common postoperative complications after pulmonary resection. The aim of this study was to reveal the incidence and risk factors of PAL in video-assisted thoracic surgery (VATS) lung cancer resection, and to evaluate the effect of PAL on postoperative complications, postoperative length of stay (PLOS), and medical costs. METHODS: Continuous patients who underwent VATS major pulmonary resection for lung cancer between January 2014 and December 2015 were studied. Clinical data of these patients were obtained from the Western China Lung Cancer Database. PAL was defined as air leak more than 5 days after surgery. The risk factors for PAL were analyzed, as well as the effect of PAL on postoperative clinical recovery. RESULTS: A total of 1,051 patients were enrolled in this study. The incidence of PAL was 10.6% (111/1,051). Pleural adhesion [odds ratio (OR), 2.38 for extensive vs. none, P=0.001] was identified as the only independent risk factors for PAL through multivariate analysis. The incidence of overall complications and pneumonia were significantly higher in patients with PAL (PAL group) than those without PAL (non-PAL group) (OR, 6.77, P=0.000; OR, 2.41, P=0.010, respectively). PAL was found to be associated with longer PLOS (11.7±6.6 vs. 6.5±3.6 days; P=0.000) and higher medical costs (¥62,042.5±18,072.0 vs. ¥52,291.3±13,845.5, P=0.000). CONCLUSIONS: Pleural adhesion was associated with increased risk of PAL after VATS lung cancer resection. Those patients with PAL had more postoperative complications, stayed longer in the hospital after surgery, and paid higher medical costs.

Effect of modeled microgravity on radiation-induced adaptive response of root growth in Arabidopsis thaliana.

Space particles have an inevitable impact on organisms during space missions; radio-adaptive response (RAR) is a critical radiation effect due to both low-dose background and sudden high-dose radiation exposure during solar storms. Although it is relevant to consider RAR within the context of microgravity, another major space environmental factor, there is no existing evidence as to its effects on RAR. In the present study, we established an experimental method for detecting the effects of gamma-irradiation on the primary root growth of Arabidopsis thaliana, in which RAR of root growth was significantly induced by several dose combinations. Microgravity was simulated using a two-dimensional rotation clinostat. It was shown that RAR of root growth was significantly inhibited under the modeled microgravity condition, and was absent in pgm-1 plants that had impaired gravity sensing in root tips. These results suggest that RAR could be modulated in microgravity. Time course analysis showed that microgravity affected either the development of radio-resistance induced by priming irradiation, or the responses of plants to challenging irradiation. After treatment with the modeled microgravity, attenuation in priming irradiation-induced expressions of DNA repair genes (AtKu70 and AtRAD54), and reduced DNA repair efficiency in response to challenging irradiation were observed. In plant roots, the polar transportation of the phytohormone auxin is regulated by gravity, and treatment with an exogenous auxin (indole-3-acetic acid) prevented the induction of RAR of root growth, suggesting that auxin might play a regulatory role in the interaction between microgravity and RAR of root growth.

Effect of modeled microgravity on UV-C-induced interplant communication of Arabidopsis thaliana.

Controlled ecological life support systems (CELSS) will be an important feature of long-duration space missions of which higher plants are one of the indispensable components. Because of its pivotal role in enabling plants to cope with environmental stress, interplant communication might have important implications for the ecological stability of such CELSS. However, the manifestations of interplant communication in microgravity conditions have yet to be fully elucidated. To address this, a well-established Arabidopsis thaliana co-culture experimental system, in which UV-C-induced airborne interplant communication is evaluated by the alleviation of transcriptional gene silencing (TGS) in bystander plants, was placed in microgravity modeled by a two-dimensional rotating clinostat. Compared with plants under normal gravity, TGS alleviation in bystander plants was inhibited in microgravity. Moreover, TGS alleviation was also prevented when plants of the pgm-1 line, which are impaired in gravity sensing, were used in either the UV-C-irradiated or bystander group. In addition to the specific TGS-loci, interplant communication-shaped genome-wide DNA methylation in bystander plants was altered under microgravity conditions. These results indicate that interplant communications might be modified in microgravity. Time course analysis showed that microgravity interfered with both the production of communicative signals in UV-C-irradiated plants and the induction of epigenetic responses in bystander plants. This was further confirmed by the experimental finding that microgravity also prevented the response of bystander plants to exogenous methyl jasmonate (JA) and methyl salicylate (SA), two well-known airborne signaling molecules, and down-regulated JA and SA biosynthesis in UV-C-irradiated plants.

Co-infection with genital gonorrhoea and genital chlamydia in female sex workers in Yunnan, China.

An observational study on prevalence of co-infection with gonorrhoea and chlamydia was conducted among female sex workers (FSWs) in Kunming, China.A total of 505 FSWs participated in the study. All eligible participants gave informed consent. Demographic, behavioural and clinical information of the participants was gathered by direct structured interviews. Tampon swabs were collected to test for Chlamydia trachomatis and Nesseria gonorrhoeae. One-hundred and twenty-four (24.6%) FSWs were co-infected with these two pathogens. Of the 191 FSWs with gonorrhea, 124 (64.9%, 95% confidence interval [CI] = 57.9-71.3%) were co-infected with chlamydia which was significantly higher than the proportion (41.9%, 95% CI = 36.4-47.6%) co-infected with gonorrhoea among 296 FSWs with chlamydia (P < 0.001). Only 47 of 191 (24.6%) FSWs with gonococcal infection and 28 of 124 (22.6%) with co-infection with gonorrhoea and chlamydia reported vaginal discharge. The results of the study justify the recommendation in the national sexually transmitted disease (STD) guidelines that patients infected with gonorrhoea also be treated routinely with an anti-chlamydial regimen. However, a periodic mass treatment may be considered in some circumstances in STD control programmes to rapidly reduce the infections in this population.

Sexually transmitted infections among female sex workers in Yunnan, China.

A cross-sectional prevalence survey of sexually transmitted infections (STIs) was conducted among female sex workers (FSWs) in Kunming, Yunnan Province, China. A total of 505 FSWs participated in the survey. All eligible participants gave informed consent. Demographic, behavioral, and clinical information of the participants was gathered by direct structured interviews. Tampon swabs were collected to test for Chlamydia trachomatis, Nesseria gonorrhoeae, and Trichomonas vaginalis and serum specimens were collected to test for HIV antibody by enzyme-linked immunosorbent assay (ELISA) screening and Western blot confirmation, syphilis with rapid plasma reagin (RPR) and T. pallidum hemagglutination (TPHA) confirmation, and for HSV-2 antibodies with the HerpeSelect 2 ELISA. The most prevalent bacterial STI was Chlamydia trachomatis (58.6%), followed by Trichomonas vaginalis (43.2%) and Neisseria gonorrhoeae (37.8%). Three hundred twenty-seven (65.1%) sex workers had serologic evidence of exposure to HSV-2 infection. Ten percent were positive for HIV infection, all injecting drug users (IDUs); and 9.5% had infection with syphilis. Comprehensive prevention and effective STI services for sex workers and their clients will be the key strategies to the control of STIs, including HIV. Policies and prevention strategies for STI/HIV need to focus on high-risk subpopulations, such as sex workers (particularly sex workers who inject drugs) and their clients.

Modulation of modeled microgravity on radiation-induced bystander effects in Arabidopsis thaliana.

Both space radiation and microgravity have been demonstrated to have inevitable impact on living organisms during space flights and should be considered as important factors for estimating the potential health risk for astronauts. Therefore, the question whether radiation effects could be modulated by microgravity is an important aspect in such risk evaluation. Space particles at low dose and fluence rate, directly affect only a fraction of cells in the whole organism, which implement radiation-induced bystander effects (RIBE) in cellular response to space radiation exposure. The fact that all of the RIBE experiments are carried out in a normal gravity condition bring forward the need for evidence regarding the effect of microgravity on RIBE. In the present study, a two-dimensional rotation clinostat was adopted to demonstrate RIBE in microgravity conditions, in which the RIBE was assayed using an experimental system of root-localized irradiation of Arabidopsis thaliana (A. thaliana) plants. The results showed that the modeled microgravity inhibited significantly the RIBE-mediated up-regulation of expression of the AtRAD54 and AtRAD51 genes, generation of reactive oxygen species (ROS) and transcriptional activation of multicopy P35S:GUS, but made no difference to the induction of homologous recombination by RIBE, showing divergent responses of RIBE to the microgravity conditions. The time course of interaction between the modeled microgravity and RIBE was further investigated, and the results showed that the microgravity mainly modulated the processes of the generation or translocation of the bystander signal(s) in roots.

Effects of HIV status notification on reducing the risk of sexual transmission of HIV in China.

BACKGROUND: The risk of HIV sexual transmission is much higher among people unaware of their HIV status than among those aware. Only a few studies have indicated that the incidence of unsafe sex can be reduced when people know their HIV status. This study was to investigate this effect in China. METHODS: A cohort study consisting of two surveys was conducted at two different times among a group of people living with HIV/AIDS, whose status was newly diagnosed with HIV via sexual contact, in Shanghai, Chongqing, and Kunming. The first survey was conducted among 823 people tested positive for HIV before notifying them of the HIV status. The second survey was conducted among 650 HIV-positive people at six months following the first survey (after notification of HIV status). The scope of survey covered unsafe sex practices, number of unsafe sexual partners, and frequency of unsafe sexual behaviors over the prior six months. Unsafe sex is defined as unprotected anal or vaginal sex with partners who are HIV positive or whose HIV status is unknown. RESULTS: The proportion of unsafe sex was reduced by about 85% after HIV status notification. The risk of HIV sexual transmission was 15 times higher among persons unaware of their HIV status than among those aware. Approximately 95% of new sexually transmitted HIV infections stemmed from 56% of the infected persons unaware of their HIV status in China. CONCLUSION: Timely HIV status notification has the potential to significantly reduce unsafe sex among HIV-infected persons and reduce the risk for HIV transmission via unsafe sex.