[專欄]淺談武漢肺炎之公共衛生風險 (下)

該研究指出，每一星期感染武漢肺炎的人數便會翻倍。

 

Basic reproductive number R₀（基本傳染數）是傳染病學常用來量度傳染性的一個metric，它指 一單感染個案在感染期間在健康的人口平均引致的額外感染個案。若數字大於1，代表該病毒會在人羣中傳播。

 

“Among the first 425 patients with confirmed NCIP, the median age was 59 years and 56% were male. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days (95% confidence interval [CI], 4.1 to 7.0), with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days [Note: 95% CI, 4.2 to 14]. With a mean serial interval of 7.5 days (95% CI, 5.3 to 19), the basic reproductive number was estimated to be 2.2 (95% CI, 1.4 to 3.9)."

 

研究得出的Basic reproductive number R₀（基本傳染數）表示，有九成五機會 基本傳染數 會介乎於1.4到3.9之間。指數大於1，足以證明武漢肺炎人傳人。

人傳人的威力如何？根據該研究，感染數字增長的預測是7天多一倍。保守一點看，最長是兩星期感染人數便翻倍。

值得注意的是，在統計學上，Confidence Interval（信心區間）介乎4.2到14，即是說有95%機會武漢肺炎會在4天到兩星期之間增加一倍。但4天到14天其實是一個相當闊的數字，Statistical evidence不是十分強。每個研究固然有先天的缺陷，此研究的method、sample size以至使用的數學模型未必能提供最好的level of evidence。但以一個對於武漢肺炎早期傳染性的研究，其數據值得引以為鑑。

 

一星期抑或是兩星期已不再重要，在沒有疫苗和藥物對策下，It’s a matter of time it goes pandemic.

(如有錯漏，歡迎指正)

 

參考:

Li Q, Guan X, Wu P, et al. Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia New England Journal of Medicine. January 29, 2020.

 

(專欄文章不代表 ManHungTech 立場)

延伸閱讀:

[專欄]淺談武漢肺炎之公共衛生風險 (上)