Identifying opportunities to enhance environmental cleaning in 23 acute care hospitals .

OBJECTIVE: The quality of environmental hygiene in hospitals is under increasing scrutiny from both healthcare providers and consumers because the prevalence of serious infections due to multidrug-resistant pathogens has reached alarming levels. On the basis of the results from a small number of hospitals, we undertook a study to evaluate the thoroughness of disinfection and cleaning in the patient's immediate environment and to identify opportunities for improvement in a diverse group of acute care hospitals. METHODS: Prospective multicenter study to evaluate the thoroughness of terminal room cleaning in hospitals using a novel targeting method to mimic the surface contamination of objects in the patient's immediate environment. SETTING: Twenty-three acute care hospitals. RESULTS: The overall thoroughness of terminal cleaning, expressed as a percentage of surfaces evaluated, was 49% (range for all 23 hospitals, 35%-81%). Despite the tight clustering of overall cleaning rates in 21 of the hospitals, there was marked variation within object categories, which was particularly notable with respect to the cleaning of toilet handholds, bedpan cleaners, light switches, and door knobs (mean cleaning rates, less than 30%; institutional ranges, 0%-90%). Sinks, toilet seats, and tray tables, in contrast, were consistently relatively well cleaned (mean cleaning rates, over 75%). Patient telephones, nurse call devices, and bedside rails were inconsistently cleaned. CONCLUSION: We identified significant opportunities in all participating hospitals to improve the cleaning of frequently touched objects in the patient's immediate environment. The information obtained from such assessments can be used to develop focused administrative and educational interventions that incorporate ongoing feedback to the environmental services staff, to improve cleaning and disinfection practices in healthcare institutions.     

Evaluation of disinfectants in the domestic environment under 'in use' conditions

An 'in use' test was developed to investigate effectiveness of disinfectant application and of detergent of hot water cleaning at kitchen, bathroom and toilet sites in the domestic environment. Detergent and hot water cleaning produced no observable reduction in microbial contamination. Single and daily application tests demonstrated that hypochlorite and phenolic disinfectants can be used to produce substantial reductions in bacterial contamination in the home. Results indicate that maximum protection afforded by disinfection is relatively brief; 3-6 h after disinfection, contamination levels were only marginally less than those observed at pretreatment. Some suggestions are made for improvements in home hygiene.     

Nosocomial infections in combined medical-surgical intensive care units in the United States.

OBJECTIVE: To describe the epidemiology of nosocomial infections in combined medical-surgical (MS) intensive care units (ICUs) participating in the National Nosocomial Infection Surveillance (NNIS) System. DESIGN: Analysis of surveillance data on 498,998 patients with 1,554,070 patient-days, collected between 1992 and 1998 from 205 MS ICUs following the NNIS Intensive Care Unit protocol, representing 152 participating NNIS hospitals in the United States. RESULTS: Infections at three major sites represented 68% of all reported infections (nosocomial pneumonia, 31%; urinary tract infections (UTIs), 23%; and primary bloodstream infections (BSIs), 14%: 83% of episodes of nosocomial pneumonia were associated with mechanical ventilation, 97% of UTIs occurred in catheterized patients, and 87% of primary BSIs in patients with a central line. In patients with primary BSIs, coagulase-negative staphylococci (39%) were the most common pathogens reported; Staphylococcus aureus (12%) was as frequently reported as enterococci (11%). Coagulase-negative staphylococcal BSIs were increasingly reported over the 6 years, but no increase was seen in candidemia or enterococcal bacteremia. In patients with pneumonia, S. aureus (17%) was the most frequently reported isolate. Of reported isolates, 59% were gram-negative bacilli. In patients with UTIs, Escherichia coli (19%) was the most frequently reported isolate. Of reported isolates, 31% were fungi. In patients with surgical-site infections, Enterococcus (17%) was the single most frequently reported pathogen. Device-associated nosocomial infection rates for BSIs, pneumonia, and UTIs did not correlate with length of ICU stay, hospital bed size, number of beds in the ICU, or season. Combined MS ICUs in major teaching hospitals had higher device-associated infection rates compared to all other hospitals with combined medical-surgical units. CONCLUSIONS: Nosocomial infections in MS ICUs at the most frequent infection sites (bloodstream, urinary, and respiratory tract) almost always were associated with use of an invasive device. Device-associated infection rates were the best available comparative rates between combined MS ICUs, but the distribution of device-associated rates should be stratified by a hospital's major teaching affiliation status.     

176所医院连续6年ICU医院感染目标性监测分析

目的了解某省二级及以上医院重症监护病房(ICU)医院感染发生情况,为医院感染管理提供依据。方法医院感染管理质量控制中心(HAIQCC)于2010年7月1日—2015年6月30日组织全省二级及以上医院开展ICU医院感染目标性监测。结果共监测176所医院的ICU,连续6年ICU医院感染发病率为7.23%,医院感染例次发病率9.72%;连续6年ICU医院感染发病率呈逐年下降趋势(P0.001)。综合医院ICU的调整例次日发病率(4.30‰)高于专科医院ICU(3.53‰)。外科ICU和综合ICU医院感染发病率较高,调整例次日发病率分别为4.79‰和4.21‰。ICU医院感染以下呼吸道、泌尿道、血流感染为主,分别占68.64%、14.45%和10.09%。中心静脉导管、呼吸机、导尿管使用率分别为49.86%、39.16%、81.95%,三管相关感染例次日发病率分别为1.74‰、13.77‰、2.08‰。连续6年三管相关感染例次日发病率逐年降低(P0.001)。呼吸机、中心静脉导管、导尿管在不同科别ICU中的使用率与其相关感染发病率均无相关性(均P0.05)。共检出病原菌36 223株,前6位病原菌依次为鲍曼不动杆菌(22.77%)、肺炎克雷伯菌(11.96%)、铜绿假单胞菌(11.94%)、金黄色葡萄球菌(8.08%)、白假丝酵母菌(5.63%)、大肠埃希菌(5.55%)。连续6年耐碳青霉烯类肺炎克雷伯菌的检出率呈上升趋势(P0.05)。结论持续开展ICU医院感染目标性监测,定期分析医院感染的高危因素,及时采取干预措施,可有效降低ICU医院感染发病率。     

Evaluation of disinfectants in the domestic environment under 'in use' conditions.

An ''in use'' test was developed to investigate effectiveness of disinfectant application and of detergent of hot water cleaning at kitchen, bathroom and toilet sites in the domestic environment. Detergent and hot water cleaning produced no observable reduction in microbial contamination. Single and daily application tests demonstrated that hypochlorite and phenolic disinfectants can be used to produce substantial reductions in bacterial contamination in the home. Results indicate that maximum protection afforded by disinfection is relatively brief; 3-6 h after disinfection, contamination levels were only marginally less than those observed at pretreatment. Some suggestions are made for improvements in home hygiene.     

An evaluation of hospital cleaning regimes and standards

A four-part study assessing cleanliness in up to 113 environmental surfaces in an operating theatre and a hospital ward is reported. Surfaces were assessed visually, using microbiological methods and ATP bioluminescence. Results from a preliminary random survey indicated variability in cleanliness. These results were then used to select sites for monitoring before and after routine cleaning, over a 14-day period. Using published microbiological and ATP specifications 70 and 76% of these sites were unacceptable after cleaning. Visual assessment was a poor indicator of cleaning efficacy with only 18% considered unacceptable. Sites most likely to fail in the ward were in the toilet and kitchen, areas which are frequently implicated in the spread of infectious intestinal disease. Operating theatre sites had lower ATP results but 61% of sites would be considered unacceptable. There was no significant difference in general microbiological or ATP results overall before and after routine cleaning. Although some important hand contact sites showed no significant difference, overall there was a significant decrease in staphylococcal and enterobacteria counts in the ward but not in the operating theatre after cleaning. The routine cleaning programmes used did not include a biocide and cleaning using a hypochlorite based sanitizer gave much lower values. The results are discussed in relation to infection control, cleaning audits and cleaning schedules: an integrated cleaning monitoring programme using ATP bioluminescence in conjunction with visual and microbiological assessments is recommended.     

Assessing the biological efficacy and rate of recontamination following hydrogen peroxide vapour decontamination

The inanimate hospital environment can become contaminated with nosocomial pathogens. Hydrogen peroxide vapour (HPV) decontamination has proven effective for the eradication of persistent environmental contamination. We investigated the extent of meticillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant enterococci (VRE) and gentamicin-resistant Gram-negative rod (GNR) contamination in a ward side-room occupied by a patient with a history of MRSA, VRE and GNR infection and colonisation and investigated the impact of HPV decontamination. Fifteen standardised sites in the room were sampled using a selective broth enrichment protocol to culture MRSA, VRE and GNR. Sampling was performed before cleaning, after cleaning, after HPV decontamination and at intervals over the subsequent 19 days on two separate occasions. Environmental contamination was identified before cleaning on 60, 30 and 6.7% of sites for MRSA, GNR and VRE, respectively, and 40, 10 and 6.7% of sites after cleaning. Only one site (3.3%) was contaminated with MRSA after HPV decontamination. No recontamination with VRE was identified and no recontamination with MRSA and GNR was identified during the two days following HPV decontamination. Substantial recontamination was identified approximately one week after HPV decontamination towards post-cleaning levels for GNR and towards pre-cleaning levels for MRSA. HPV is more effective than standard terminal cleaning for the eradication of nosocomial pathogens. Recontamination was not immediate for MRSA and GNR but contamination returned within a week in a room occupied by a patient colonised with MRSA and GNR. This finding has important implications for the optimal deployment of HPV decontamination in hospitals.     

高频接触物体表面清洁质量的调查

目的了解某院高频接触物体表面清洁质量,以制订有效的循证干预措施。方法2014年10月-2015年2月应用荧光胶剂对该院普通病房、手术室、重症监护病房（ICU）高频接触物体表面进行标记,每周1～2次,于患者出院前、手术结束后进行标记,清洁后检查物体表面清洁质量。结果共监测物体表面2 131处,清除1 732处,清除率为81.3%,卫生清洁质量处于合格状态。普通病区监测642处,清除率达82.1%;手术室监测650处,清除率75.8%;ICU区监测839处,清除率84.9%,3个病区物体表面清除率比较,差异有统计学意义（χ2 =19.964,P＜0.001）。普通病区呼叫按钮、电开关和设备带清除率分别是51.3%、55.2%和58.5%,手术室墙和麻醉机控板、摇床器、键盘和输液泵的卫生清除率分别是38.6%、48.8%、60.0%、61.3%、68.4%,ICU设备带的清除率为65.9%,均处于不合格状态。结论该院环境卫生清洁质量总体处于合格状态,但仍有需要改进的地方,该院高频接触物体表面的清洁质量有待进一步提高。     

A microbiological evaluation of hospital cleaning methods

Hospital hygiene may be associated with hospital-acquired infection. This study evaluated four hospital cleaning methods: 'mop and vacuum', 'spray clean' and 'wet scrub' for floors, and one steam cleaning method for curtains. A standardised microbiological screening method was used to sample the environment before and after cleaning in order to quantify total viable counts as well as identify specific organisms. The results showed that all floor cleaning methods reduced the overall microbial load, although high counts and bacterial pathogens occasionally persisted despite cleaning. Spray cleaning gave marginally better results than traditional mopping and vacuuming. Wet scrubbing significantly reduced levels of coagulase-positive staphylococci (p = 0.03), which, in combination with routine methods, produced an effect that persisted for at least a week. Steam cleaning of curtains also reduced microbial counts (p = 0.08), but had little effect on Staphylococcus aureus and other potential pathogens. These results might help managers assess the costs of different cleaning methods against potential infection control benefits in a hospital.     

某三甲医院131I治疗场所辐射水平调查

目的 对某三甲医院¹³¹I治疗场所辐射水平进行检测,了解其辐射水平。方法 25名甲癌患者共服用82880 MBq的¹³¹I。患者服药后用X、γ射线测量仪检测病房周围剂量当量率;出院后用α、β表面污染仪检测病房表面污染;治疗期间和出院当天对¹³¹I治疗场所及办公区进行空气采样,用高纯锗γ能谱仪测量空气样品,数据处理后得到空气中¹³¹I浓度。结果 ¹³¹I治疗病房周围剂量当量率为0.15～0.46 μSv/h。病房清理前表面污染为0.53～40.1 Bq/cm²,其中马桶最高。患者服药后4 h内,¹³¹I治疗场所及办公区走廊空气中¹³¹I浓度分别为1.74 Bq/m³和0.66 Bq/m³。¹³¹I治疗场所排风速率为0.50 m/s。患者治疗期间及出院当天,因通风导致空气中的¹³¹I浓度分别较前一天下降29.7%、79.7%和53.3%。结论 该场所外照射辐射水平较低且屏蔽效果较好;¹³¹I治疗病房清理前表面污染除马桶略高于标准要求外,其余均低于标准限值;通风是降低该场所空气中¹³¹I浓度的主要途径。     

ICU患者医院感染危险因素监测分析

目的 了解重症监护病房(ICU)内医院感染危险因素，以制定有效控制措施，减少医院感染的发生。方法 对ICU住院患者进行为期1年的前瞻性监测。监测期为患者进入ICU至转出ICU72h。由专职人员每日巡视ICU内住院患者，填写相应登记表。结果 共监测661例病例，医院感染率为14．98％，各科ICU医院感染率由高到低依次为：内科46．08％，老年病科23．46％，外科18．11％，心内科11．11％。医院感染部位前3位是：下呼吸道(58．59％)，胃肠道(17．19％)，泌尿道(10．94％)。医院感染病原菌前3位是：铜绿假单胞菌(26．23％)，金黄色葡萄球菌(16．39％)，表皮葡萄球菌(13．11％)。结论 尽可能缩短住ICU时间，注意各种侵入性操作的消毒隔离并尽早停止侵入性操作，合理使用抗菌药物是减少ICU内医院感染率的有效措施。     

Finding a benchmark for monitoring hospital cleanliness

This study evaluated three methods for monitoring hospital cleanliness. The aim was to find a benchmark that could indicate risk to patients from a contaminated environment. We performed visual monitoring, ATP bioluminescence and microbiological screening of five clinical surfaces before and after detergent-based cleaning on two wards over a four-week period. Five additional sites that were not featured in the routine domestic specification were also sampled. Measurements from all three methods were integrated and compared in order to choose appropriate levels for routine monitoring. We found that visual assessment did not reflect ATP values nor environmental contamination with microbial flora including Staphylococcus aureus and meticillin-resistant S. aureus (MRSA). There was a relationship between microbial growth categories and the proportion of ATP values exceeding a chosen benchmark but neither reliably predicted the presence of S. aureus or MRSA. ATP values were occasionally diverse. Detergent-based cleaning reduced levels of organic soil by 32% (95% confidence interval: 16-44%; P<0.001) but did not necessarily eliminate indicator staphylococci, some of which survived the cleaning process. An ATP benchmark value of 100 relative light units offered the closest correlation with microbial growth levels <2.5 cfu/cm(2) (receiver operating characteristic ROC curve sensitivity: 57%; specificity: 57%). In conclusion, microbiological and ATP monitoring confirmed environmental contamination, persistence of hospital pathogens and measured the effect on the environment from current cleaning practices. This study has provided provisional benchmarks to assist with future assessment of hospital cleanliness. Further work is required to refine practical sampling strategy and choice of benchmarks.     

Effectiveness of UV-C light irradiation on disinfection of an eSOS® smart toilet evaluated in a temporary settlement in the Philippines

Ultraviolet germicidal (short wavelength UV-C) light was studied as surface disinfectant in an Emergency Sanitation Operation System^® smart toilet to aid to the work of manual cleaning. The UV-C light was installed and regulated as a self-cleaning feature of the toilet, which automatically irradiate after each toilet use. Two experimental phases were conducted i.e. preparatory phase consists of tests under laboratory conditions and field testing phase. The laboratory UV test indicated that irradiation for 10 min with medium–low intensity of 0.15–0.4 W/m² could achieve 6.5 log removal of Escherichia coli. Field testing of the toilet under real usage found that UV-C irradiation was capable to inactivate total coliform at toilet surfaces within 167-cm distance from the UV-C lamp (UV-C dose between 1.88 and 2.74 mW). UV-C irradiation is most effective with the support of effective manual cleaning. Application of UV-C for surface disinfection in emergency toilets could potentially reduce public health risks.     

Efficacy of point-of-entry copper--silver ionisation system in eradicating Legionella pneumophila in a tropical tertiary care hospital: implications for hospitals contaminated with Legionella in both hot and cold water

A medical centre in Southern Taiwan experienced an outbreak of nosocomial Legionnaires' disease, with the water distribution system thought to be the source of the infection. Even after two superheats and flush, the rate of Legionella positivity in distal sites in hospital wards and intensive care units (ICUs) was 14% and 66%, respectively. Copper-silver ionisation was therefore implemented in an attempt to control Legionella colonisation in both hot- and cold-water systems. Environmental cultures and ion concentration testing were performed to evaluate the efficacy of ionisation. When the system was activated, no significant change in rate of Legionella positivity in the hospital wards (20% vs baseline of 30%) and ICUs (28% vs baseline of 34%) of the test buildings over a three-month period was found, although all Legionella positivity rates were below 30%, an arbitrary target for Legionnaires' disease prevention. When ion concentrations were increased from month 4 to month 7, however, the rate of Legionella positivity decreased significantly to 5% (mean) in hospital wards (P=0.037) and 16% (mean) in ICUs (P=0.037). Legionella positivity was further reduced to 0% in hospital wards and 5% (mean) in ICUs while 50% sites were still positive for Legionella in a control building. Although Legionella was not completely eradicated during the study period, no culture- or urine-confirmed hospital-acquired Legionnaires' disease was reported. Ionisation was effective in controlling Legionella for both hot and cold water, and may be an attractive alternative as a point-of-entry systematic disinfection solution for Legionella.     

山东省101所医院重症监护病房患者分离细菌及耐药性特征

目的了解山东省重症监护病房(ICU)细菌分布及耐药情况。方法收集2014年山东省101所医院ICU及106所医院普通病房(非ICU)分离细菌的药敏数据,进行统计分析。结果共收集细菌24 458株,革兰阴性菌占80.37%,革兰阳性菌占19.63%。ICU分离居前5位的细菌依次为:肺炎克雷伯菌、鲍曼不动杆菌、铜绿假单胞菌、大肠埃希菌、金黄色葡萄球菌。来源于ICU的大肠埃希菌、肺炎克雷伯菌、阴沟肠杆菌、黏质沙雷菌对碳青霉烯类药物、哌拉西林/他唑巴坦、头孢哌酮/舒巴坦、阿米卡星耐药率高于非ICU来源菌株(均P0.01)。ICU分离鲍曼不动杆菌、铜绿假单胞菌、葡萄球菌属细菌对常用抗菌药物耐药率高于非ICU菌株(P0.05)。ICU分离鲍曼不动杆菌对亚胺培南和美罗培南耐药率分别为78.0%、79.0%;铜绿假单胞菌对前述药物耐药率分别为25.5%、21.6%,对其他常用抗菌药物的耐药率30.0%。ICU耐甲氧西林金黄色葡萄球菌(MRSA)检出率为39.7%,高于非ICU的26.0%(P0.05)。结论 ICU分离细菌耐药情况比较严重,应依据药敏结果指导抗菌药物合理应用,防止耐药菌感染扩散。     

新生儿重症监护病房医院感染流行病学多中心研究

目的了解我国三级甲等综合医院新生儿监护病房(NICU)医院感染的流行特点,为预防和控制新生儿医院感染提供科学依据。方法以多中心研究的方式,选取全国9省17所医院,按照统一的诊断标准和方法对2013年10月—2014年9月NICU住院新生儿的医院感染情况进行前瞻性监测。结果共监测 12 998例NICU住院新生儿,发生436例次医院感染,例次发病率为3.35%,住院总日数为126 125 d,日发病率为3.46‰。新生儿医院感染例次发病率随新生儿出生体重的增加而下降（χ2=291.55,P＜0.001）。不同规模NICU新生儿医院感染发病率比较,差异有统计学意义（χ2=49.77,P＜0.001）,床位数＞30张的NICU新生儿医院感染例次发病率和日发病率最高;NICU新生儿医院感染例次发病率以西南地区（10.36%）最高,日发病率以华南地区（10.52‰）最高。感染部位以下呼吸道和血液为主;感染病原体以肺炎克雷伯菌、大肠埃希菌、鲍曼不动杆菌为主。结论我国NICU不同出生体重组、不同规模、不同地区的新生儿医院感染发病率不同,应继续加强监测,根据感染特点指导各项防控措施的落实。     

Impact of a five-year surveillance of central venous catheter infections in the REACAT intensive care unit network in France

Central venous catheter (CVC)-related infections (CRIs) are a key target for infection control in intensive care units (ICUs). The aim of this study was to describe temporal trends of CRI incidence in a network of volunteer ICUs in Northern France. During a 4 month surveillance period each year, all CVCs in place for more than 48h were prospectively followed until removal or patient discharge. Standard clinical and microbiological criteria were used to define colonization and CRI. The standardized incidence ratio (SIR) was estimated by dividing the number of observed CRIs by the number of expected CRIs, which was computed using a logistic regression model including risk factors for CRI. CRI incidence and SIR were fed back to ICUs as a benchmark at the end of each period. From 2001 to 2005, 135 ICUs participated for at least one surveillance period. Overall, 11 703 CVC in 9182 patients (122 495 CVC-days) were included. CRI incidence was 2.8 per 1000 CVC-days. Among 35 ICUs that participated for three or more consecutive periods, CRI incidence decreased significantly by 58.6%. SIR also decreased significantly from the first to the third surveillance period in these ICUs. These results suggest that surveillance programmes have a significant impact on CRI risk in ICUs and remain an important strategy for combating nosocomial infections in these settings.     

静脉用药调配中心转运药箱清洁消毒方法及效果研究

目的 对静脉用药调配中心(PIVAS)转运药箱的清洁消毒方法及效果维持时间进行研究,以保证患者的成品输液安全.方法 选取某院正常使用中的转运药箱64个,采用医用消毒湿巾清洁消毒后,分别于0、12、24、36、48 h进行目视检测和微生物检测,并进行统计分析.结果 清洁消毒0 h后,目测法和微生物检测法检测结果合格率均为...     

Hand rub consumption and hand hygiene compliance are not indicators of pathogen transmission in intensive care units

The objective of this study was to investigate whether nosocomial infection (NI) rates, hand hygiene compliance rates and the amount of alcohol-based hand rub used for hand disinfection are useful indicators of pathogen transmission in intensive care units (ICUs), and whether they could be helpful in identifying infection control problems. All isolates of 10 of the most frequent pathogens from patients who were hospitalized in an ICU for >48 h were genotyped to identify transmission episodes in five ICUs. The incidence of transmission was correlated with hand hygiene compliance, hand rub consumption and NI rates. The incidence of transmission episodes varied between 2.8 and 6.8 in the five ICUs. The NI rate was 8.6-22.5 per 1000 patient-days, hand hygiene compliance was 30-47% and hand rub consumption was 57-102 L per 1000 patient-days. There was no correlation between the incidence of transmission episodes and hand rub consumption or hand hygiene compliance. The correlation between transmission rates and NI rates was 0.4 (P = 0.5), and with the exclusion of one ICU, it was 1 (P < 0.01). The incidence of NI is a relatively good indicator for the identification of pathogen transmissions, but hand rub consumption and hand hygiene compliance, at least with the relatively low level of compliance found in this study, are not indicators of pathogen transmission.     

Creating a culture of clinical excellence in critical care nutrition: the 2008 "Best of the Best" award

Objective: To develop, validate, and implement a system to reward top performers in critical care nutrition practice and to illuminate characteristics of top‐performing intensive care units (ICUs). Design: An international, prospective, observational, cohort study conducted in May 2008. Setting: 179 ICUs from 18 countries. Patients: 2956 consecutively enrolled mechanically ventilated adult patients who stayed in the ICU for at least 72 hours. Interventions: To qualify for the “Best of the Best” (BOB) award, sites had to have implemented a nutrition protocol and contributed complete data on a minimum of 20 patients. Measurements and Main Results: Data on nutrition practices were collected from ICU admission to ICU discharge for a maximum of 12 days. Eligible sites were ranked based on their performance on the following 5 criteria: adequacy of provision of energy, use of enteral nutrition (EN), early initiation of EN, use of promotility drugs and small bowel feeding tubes, and adequate glycemic control. Of the 179 participating ICUs, 81 qualified for the BOB award. Overall, the average nutrition adequacy across sites was 56.2% (site range, 20.3%‐90.1%). The top 10 performers were identified and publicly recognized. Regression analysis suggested that the presence of a dietitian in the ICU was associated with a high BOB award ranking, whereas being located in the United States or China, relative to other participating countries, was associated with worst performance. Conclusions: There is variable performance with respect to critical care nutrition practices across the world.