Transmission in Latent Period Causes A Large Number of Infected People in the United States

The cumulative number of confirmed cases in the United States exceeded one million on 29 April 2020, becoming the country of the most serious pandemic in the world. We proposed a model to analyze the real situation and follow-up trend of the epidemic in the US. The proposed model divides the epidemic period into two phases, and includes three different categories of transmitters: the latent population, the documented infectious population, and the undocumented infectious population. We use metapopulation network to simulate the spread of the COVID-19 in the US, and apply the Bayesian inference to estimate the key parameters of the model. We also perform component analysis and sensitivity analysis, researching the compositions of the people with COVID-19. The results show that the basic reproduction number in the early period of propagation is 4.06. As of April 13, 2020, only 45% (95% CI: 35% - 73%) of symptom onset cases in the United States were documented. The incubation period of COVID-19 is 10.69 days (95% CI: 10.02 - 11.74). If the current level of interventions is continued, the cumulative number of confirmed cases is expected to reach more than 1.7 million in July and continue to grow.

Assessing the Global Tendency of COVID-19 Outbreak

COVID-19 is now widely spreading around the world as a global pandemic. In this report, we estimated the global tendency of COVID-19 and analyzed the associated global epidemic risk, given that the status quo is continued without further measures being taken. Based on official data of confirmed and recovered cases until May 21, 2020, the results showed that the global R0, excluding China, was estimated to be 2.76 (95% CI: 2.57 - 2.95). The United States, Germany, Italy, and Spain have peak values over 100,000. Using dynamical model and cluster analysis, we partition the globe into four regional epicenters of the outbreak: Southeast Asia extending southward to Oceania, the Middle East, Western Europe, and North America. Among them, Western Europe would become the major center of the outbreak. The peak values in Germany, Italy, and Spain were estimated to be 228,000, 291,000, and 298,000, respectively. Based on the current control measures by May 21, 2020, the peak value in the United States will reach 2,114,000. The cumulative number of 51 mainly researched countries patients might finally attain 6,542,000 (95% CI: 4,772,000 - 40,735,000). We also estimated the diagnosis rate, recovery rate, and infection degree of each country or region, and used clustering algorithm to retrieve countries or regions with similar epidemic characteristics. Several suggestions have been proposed for countries or regions in different clusters.

Estimating the Efficacy of Traffic Blockage and Quarantine for the Epidemic Caused by 2019-nCoV (COVID-19)

BackgroundSince the 2019-nCoV (COVID-19) outbreaks in Wuhan, China, the cumulative number of confirmed cases is increasing every day, and a large number of populations all over the world are at risk. The quarantine and traffic blockage can alleviate the risk of the epidemic and the infections, henceforth evaluating the efficacy of such actions is essential to inform policy makers and raise the public awareness of the importance of self-isolation and quarantine. MethodWe collected confirmed case data and the migration data, and introduced the quarantine factor and traffic blockage factor to the Flow-SEIR model. By varying the quarantine factor and traffic blockage factor, we simulated the change of the peak number and arrival time of infections, then the efficacy of these two intervation measures can be analyzed in our simulation. In our study, the self-protection at home is also included in quarantine. ResultsIn the simulated results, the quarantine and traffic blockage are effective for epidemic control. For Hubei province, the current quarantine factor is estimaed to be 0.405, which means around 40.5% of suceptibles who are close contacting with are in quarantine, and the current traffic blockage factor is estimaed to be 0.66, which indicates around 34% of suceptibles who had flowed out from Hubei. For the other provinces outside Hubei, the current quarantine factor is estimated to be 0.285, and the current traffic blockage factor is estimated to be 0.26. With the quarantine and traffic blockage factor increasing, the number of infections decrease dramatically. We also simulated the start dates of quarantine and traffic blockage at four time points, the simulated results show that the early of warning is also effective for epidemic containing. However, provincial level traffic blockage can only alleviate 21.06% - 22.38% of the peak number of infections. In general, the quarantine is much more effective than the traffic blockage control. ConclusionBoth of quarantine and traffic blockage are effective ways to control the spread of COVID-19. However, the eff icacy of quarantine is found to be much stronger than that of traffic blockage. Considering traffic blockage may also cause huge losses of economy, we propose to gradually deregulate the traffic blockage, and improve quarantine instead. Also, there might be a large number of asymptomatic carriers of COVID-19, the quarantine should be continued for a long time until the epidemic is totally under control.

EPIDEMIC TRENDS ANALYSIS AND RISK ESTIMATION OF 2019-NCOV OUTBREAK

Since December 1, 2019, the spread of COVID-19 is increasing every day. It is particularly important to predict the trend of the epidemic for the timely adjustment of the economy and industries. We proposed a Flow-SEHIR model in this paper to perform the trends of 2019-nCoV (COVID-19) in China. The results show that the number of daily confirmed new cases reaches the inflection point on Feb. 6 - 10 outside Hubei. For the maximum of temporal infected cases number, the predicted peak value in China except Hubei was estimated to be 21721 (95% CI: 18764 - 24929). The peak arrival time is on March 3 - 9. The temporal number of patients in most areas of China outside Hubei will peak from March 12 to March 15. The peak values of more than 73.5% provinces or regions in China will be controlled within 1000. According to Flow-SEHIR model and estimations from the data of evacuation of nationals from Wuhan, the real peak cumulative number of patients in Hubei is estimated to be 403481 (95% CI: 143284 - 1166936).

Kyphoplasty with movement and secondary enlargement of balloon for compression fracture of vertebral body with im-complete posterior wall / 中华骨科杂志

Objective To explore the clinical efficacy and indications of kyphoplasty with movement and secondary en?largement of balloon for the compression fracture of vertebral body with ruptured posterior wall. Methods A retrospective analy?sis was carried out on the data of 29 patients (10 males, 19 females;age range:55-86 years old;mean age:71 years old;29 verte?bral bodies in total) who suffered from compression fracture of the thoracolumbar spine and below, and underwent kyphoplasty through the movement and secondary enlargement of balloon within the vertebral body and were followed up from January 2011 to November 2014. These patients had backache, accompanied by lowered support, limitation of movement, no symptom of nervous lesion on both lower extremities and no past history of balloon kyphoplasty. All fractured vertebral bodies were at T 11 or below, in?cluding 1 case at T11, 4 cases T12, 11 cases L1, 9 cases L2 and 4 cases L3. The causes of injury included fall (19 cases), car accident (8 cases) and unknown reasons (2 cases). All patients underwent kyphoplasty with the movement and secondary enlargement of bal?loon within the vertebral body. Photos were taken immediately after the surgery, at 1 month, 3 months, 6 months and 12 months, and these patients were assessed and analyzed in terms of vertebral height, Cobb angle, visual analogue score (VAS) and Oswestry disability index (ODI). Results The operation time (including the formation and solidification of bone cement) of 29 patients was 40 to 65 min and the mean time was 55 ± 7 min;the blood loss during operation was 2 to 15 ml and the mean blood loss was 5 ± 2 ml;the injected volume of bone cement was 2.5-7.5 ml and the mean volume was 5.5±0.5 ml. Post?operative pain was relieved and ambulation was performed under the protection of lumbar orthosis brace. Statstical analysis was conducted on VAS, ODI, vertebral height and Cobb angle before operation and at 1 month, 3 months, 6 months and 12 months after operation, showing statistically significant differences. X ray examination found that there was no alternation or displacement of bone cement location, and no change in vertebral morphology, the vertebral height and cobb angle remained the post?operative status, and posterior wall rupture of the vertebral body was recovered well. CT revealed that the morphology of bone cement was irregular and closely integrated with bone substance, and no cavity or fissure was seen. Conclusion Kyphoplasty with movement and secondary enlargement of bal?loon within the vertebral body has a good, definite clinical efficacy in treating compression vertebral fracture with incomplete pos?terior wall of the vertebral body without obvious displacement of fractured bone and symptom of nervous lesion on both lower ex?tremities. This surgery is easy to operate, and has an immediate analgesic effect, which could recover vertebral height as well as re?duce kyphosis deformity and improve patient’s prognosis.

The application of double balloon dilation in percutaneous kyphonplasty to vertebral compression fractures / 中华骨科杂志

Objective To evaluate the clinical effectiveness of double balloon dilation in percutaneous kyphonplasty on curing vertebral?compression fractures. Methods From January 2009 to September 2013, 84 patients (94 vertebral bodies) with vertebral compression were treated by percutaneous kyphonplasty. All were fresh fractures and were injured or obvious low back pain 1 month, accompanied by local tenderness, kowtow attack painful, lumbar mobility, but no lower extremity injury numbness, activities and defecation disorders. After randomization, the double balloon dilation in percutaneous kyphonplasty method was used to treat 44 patients (49 vertebrae). In the process of performing percutaneous unilateral pedicle puncture and balloon dilata?tion of the vertebral body, the balloon has been moved some distance in the vertebral body. Then completed the perfusion of bone cement, vertebral body forming. 40 cases (45 vertebrae) were used conventional unilateral percutaneous kyphonplasty to vertebtal compression fractures. Recorded the operation time, amount of bleeding, bone?cement injection volume. Used visual analogue scale (VAS), the height of the vertebral body and Cobb angle to evaluated the curative effect. Results All 84 patients completed the operation, follow?up time was 22 months (18-24 months). In two mobile open expansion group, the operation time was about 48 min. The amount of bleeding was 8-15 ml. The average bone?cement injection volume was 5.1 ml. No patients quit the study and no bone cement?leakage cases or other side effects were observed , and no clinical accidents occurred. In a single stretching group, 40 cases (45 vertebrae) completed conventional vertebroplasty, the time of 44 min, bone cement average injection rate 3.2 ml, bleeding 10-15 ml. In two mobile open expansion group, the VAS score was 8.5 points, the height of the vertebral body height was 2.1cm, and the Cobb angle was 34°. After operation, the VAS score 2.9 points, the height of the vertebral body 2.8 cm, and Cobb 20° . In the other group, the pain was significantly relieved and the relief was satisfactor after operation.Vertebral height of 2 cm turned to the last follow?up of 2.4 cm. The Cobb angle was 32°, and the last follow?up was 27°. The VAS score, operation time and bleeding volume of the two groups were not statistically significant, and a statistically significant difference of the average bone ce?ment injection volume, postoperative vertebral height and cobb angle improved with statistical significance. A single open group were 2 cases of bone cement leakage and leakage, 1 cases of bone cement tail, the complication rate was 5.6%. Conclusion The application of double balloon dilation in percutaneous kyphonplasty to vertebral?compression fractures improve relocation of verte?bral compression fractures, increase recovery of vertebral height, and more effectively strengthen and stiffen pathological vertebral bodies, while improving kyphosis. Moreover, it can reduce pressure during bone?cement injections, minimizing the chance of over?flow and leakage, as well as the related side effects, but it will also result in an increase of bone cement?injection volume.