【解説】新型コロナウイルス「大半は軽度」　中国大規模調査

【北京ＡＦＰ＝時事】中国疾病対策予防センターは、中国で新型コロナウイルス「COVID‐19」に感染した患者の大半の症状は軽度だとの調査結果を発表した。危険性が最も高いのは、高齢者と基礎疾患がある人だという。（写真は資料写真）
　中華流行病学雑誌に掲載された論文は２月１１日時点で、中国国内で新型コロナウイルスへの感染が確認された、疑いがある、臨床診断済みまたは無症状の人計７万２３１４人を対象に調べたもの。
　今回の調査は、２０１９年１２月末に新型コロナウイルスの流行が始まって以来、最大規模となる。
　論文の主要点をまとめた。

■リスクが高いのは高齢者と基礎疾患のある人
　症状については全体の約８０．９％が軽度、１３．８％が重度で、致命的と分類された人は４．７％にとどまった。致死率が最も高いのは８０歳以上の人で１４．８％だった。
　基礎疾患がある人で致死率が最も高いのは心疾患の人で、次いで糖尿病、慢性呼吸器疾患、高血圧の順だった。
　９歳以下の子どもの死亡例はないが、母親を通じて感染した新生児の症例は少なくとも２例分かっている。
　３９歳以下の患者の致死率は０．２％で、依然として低い水準にとどまっている。致死率は年齢とともに上昇する。４０代は０．４％、５０代は１．３％、６０代は３．６％、７０代は８．０％だった。また、男性の致死率は２．８％で、女性の１．７％を上回っている。新型コロナウイルスによる全体の致死率は２．３％。
　新型コロナウイルスによる感染症患者の８６％近くが、湖北省武漢在住または滞在歴があった。新型コロナウイルスの発生源と考えられる武漢の海鮮市場では、野生動物の違法取引が行われていた。武漢は先月２３日から封鎖されている。
　新型コロナウイルスの流行は、１月２４日から２６日の間に「最初のピーク」に達したと、論文は指摘している。
　論文ではまた、２月１１日以降は全体の流行曲線（エピデミックカーブ）に「減少傾向」がみられると示唆している。これは新型コロナウイルスの広がりが、特に湖北省以外で減速していることを意味する。

■「流行再燃の可能性」
　新型コロナウイルスは１月末の春節（旧正月）の休暇で、数億人もの人が中国国内を移動したことに伴い拡散した。
　現在多くの人が休暇から戻っており、中国は「流行が再燃する可能性」に備える必要があると、論文の執筆者らは警告している。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2020/02/19-12:39）

Most people infected by the new coronavirus in China have mild symptoms, with older patients and those with underlying conditions most at risk from the disease, according to a study by Chinese researchers.
The disease has now killed nearly 1,900 people and infected more than 72,000 in China since it first emerged in the central city of Wuhan late last year.
A paper published in the Chinese Journal of Epidemiology looked at 72,314 confirmed, suspected, clinically diagnosed, and asymptomatic cases of COVID-19 illness across China as of February 11.
It is the biggest study on novel coronavirus patients since the outbreak began in late December.
Here are the main findings from the paper by the Chinese Centre for Disease Control and Prevention (CCDC):
Elderly, sick at risk:
Some 80.9 percent of infections are classified as mild, 13.8 percent as severe and only 4.7 percent as critical.
The highest fatality rate is for people aged 80 and older, at 14.8 percent.
The study finds that patients with cardiovascular disease are most likely to die of complications from the novel coronavirus, followed by patients with diabetes, chronic respiratory disease and hypertension.
There were no deaths among children aged up to 9, despite at least two cases of newborn babies infected through their mothers.
Up to age 39, the death rate remains low at 0.2 percent.
The fatality rate increases gradually with age. For people in their 40s it is 0.4 percent, in their 50s it is 1.3 percent, in their 60s it is 3.6 percent and their 70s it is 8.0 percent.
Men are more likely to die (2.8 percent) than women (1.7 percent).
The overall death rate from the virus stood at 2.3 percent.
'Wuhan exposure'
Nearly 86 percent of those who have contracted the illness had either lived in or travelled to Wuhan, where a seafood market that illegally sold wild animals is believed to be the original source of the virus.
The city in central China's Hubei province has been under lockdown since January 23.
Risk to medical workers
A total of 3,019 health workers have been diagnosed, 1,716 of whom were confirmed cases, and five had died as of February 11, the report said.
An analysis of 1,688 severe cases among medical staff showed that 64 percent of them were working in Wuhan.
The percentage of severe cases among Wuhan medical staff has gradually decreased from 38.9 percent at the peak (on January 28) to 12.7 percent in early February, the report said.
A hospital director in Wuhan died from the illness on Tuesday.
Earlier this month Wuhan ophthalmologist Li Wenliang, who had been punished by authorities for sounding the alarm about the virus, also died.
'Downward trend'
The epidemic reached its first peak between January 24 and 26, the report said.
It suggests there is has been a downward trend in the overall epidemic curve since February 11 -- meaning the spread of the disease, especially outside Hubei province, was slowing.
On February 13, China broadened its definition of confirmed cases to include those who were clinically diagnosed through lung imaging, in addition to those with a positive lab test result.
The report hints that China's decision to lock down Wuhan -- a city of 11 million people -- and impose strict transport curbs in other affected areas may have paid off.
'Possible rebound'
The virus spread as millions of people criss-crossed the country for the Lunar New Year holiday in late January.
The authors warn that with many people returning from the holiday, the country needs to brace itself for a possible rebound of the epidemic.
Coronaviruses may continue to adapt over time and become more virulent, the report warns and urges doctors to remain vigilant.