Several mechanisms driving SARS-CoV-2 transmission remain unclear. Based on individual records of 1178 potential SARS-CoV-2 infectors and their 15,648 contacts in Hunan, China, we estimated key transmission parameters. The mean generation time was estimated to be 5.7 (median: 5.5, IQR: 4.5, 6.8) days, with infectiousness peaking 1.8 days before symptom onset, with 95% of transmission events occurring between 8.8 days before and 9.5 days after symptom onset. Most transmission events occurred during the pre-symptomatic phase (59.2%). SARS-CoV-2 susceptibility to infection increases with age, while transmissibility is not significantly different between age groups and between symptomatic and asymptomatic individuals. Contacts in households and exposure to first-generation cases are associated with higher odds of transmission. Our findings support the hypothesis that children can effectively transmit SARS-CoV-2 and highlight how pre-symptomatic and asymptomatic transmission can hinder control efforts.

Osteosarcoma (OS) is the most common type of primary bone tumor in children and adolescents and has been associated with a high degree of malignancy, early metastasis, rapid progression and poor prognosis. However, the use of adjuvant chemotherapy improves the prognosis of patients with OS. OS chemotherapy is based primarily on the use of adriamycin, cisplatin (DDP), methotrexate (MTX), ifosfamide (IFO), epirubicin (EPI) and other drugs. Previous studies have revealed that the survival rate for patients with OS appears to have plateaued: 5-year survival rates remain close to 60%, even with the use of combined chemotherapy. The most limiting factors include complications and fatal toxicity associated with chemotherapy agents, particularly high-dose MTX (HD-MTX), for which high toxicity and great individual variation in responses have been observed. Docetaxel (TXT) is a representative member of the relatively recently developed taxane class of drugs, which function to inhibit OS cell proliferation and induce apoptosis. Recently, more clinical studies have reported that TXT combined with gemcitabine (GEM) is effective in the treatment of OS (relapse/refractory and progressive), providing evidence in support of potential novel treatment strategies for this patient population. However, there is still no global consensus on this type of chemotherapy approach. The present review summarizes current studies surrounding progress in the chemotherapeutic treatment of OS and discusses the advantages and potential feasibility of TXT+GEM in the treatment of OS.

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