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武漢新型冠狀病毒疫情系列之四 — 捐血

2020/2/23 — 12:33

新型冠狀病毒似乎因為外國出現一些案例和外國專家研究,令人們對它的特性更加了解。很多人不相信中國官方通報的數字,但是主要的病例來自大陸,不少外國的專家都是依靠大陸數據的。就算大陸報細數,我們還是可以從它的數字了解到這疫情的發展趨勢,因為所有數字都加權講大話,其走向趨勢圖是不會改變的。自從習近平發表講話,高調做了中國防疫的總指揮後,中國衞生健康委員會公佈的數字相當混亂。

這讓人想起托爾斯泰的名著《戰爭與和平》中的一片段。沙皇時期的俄軍統帥在對付拿破侖大軍時,因為從來不發表指示,反而令沙皇軍隊大勝拿破侖。這故事說出來,高高在上的大人們往往是廢物,不出聲反而幫了忙。看來,習近平學不到這教訓,還妄想定於一尊。

在香港的沙士時期,落錯藥做成一些枉死。今次香港出現的一宗死亡個案,看來有機會落錯藥。新型肺炎的危殆至死亡是因為肺部被嚴重破壞,突然死亡的較罕見。

廣告

官僚永遠沒有遠見,在沙士期間,民間一直懷疑老鼠帶著病毒。現時已有例證是新型冠狀病毒患者的排泄物可以但不必然帶病毒。青衣長康邨食肆林立,後巷的衞生一直不好,居民常常投訴鼠患。香港正值進入春季,春天回暖是老鼠的繁殖期,鼠患會突然爆發,香港進行全面滅鼠刻不容緩。現居美國的流行病學專家、公共衞生博士吳錦祥醫生撰文呼籲當局檢查老鼠攜帶病毒散播社區的可能性 (註一)。

習近平的高調介入似乎成了一些國內醫療機構好大喜功的一個誘因,其中一個例子是武漢一間醫院院長呼籲「過來人」捐血。值得注意的是,發表血清有效的是一間上巿的大陸醫療集團「中國生物技術公司」,這與其利益有關連,01177的股價稍有上升 (註二)。

廣告

人體免疫機制 (註2)

<殺手T細胞>

當病毒入侵人體,它會進入體內細胞,大量繁殖後進一步作惡。這些受了感染的細胞會在其外層發出某種蛋白以顯示其已受感染,人體內原有的殺手T細胞就會將這些舉旗的受感染細胞殲滅。

<干擾素>

受感染細胞可以產生一種蛋白質,叫干擾素。干擾素可以妨礙受感染細胞分裂,從而干擾了病毒的擴散,它也可以提醒鄰近細胞,預早進入作戰狀態。

<抗體>

抗體(血清)是在病毒尚未進入健康細胞的防禦機制,它將病毒綑綁一起,並將之殲滅。

一位流行病學專家的意見

一位流行病學專家以英文 (註4) 發表了對抽抗體作治療用途的意見,筆者節譯如下:

「抗體(血清)只能在病毒尚未進入細胞之前有效,但病毒進入人體內很快就侵入細胞,所以這類療法的功效很有限,而且,能夠從復元者體內抽出的血清份量很少,這種抽血清的程序相當繁複,要求的安全標準甚高,通常這是紅十字會的工作,湖南愛滋村醜聞就是因為抽血清導致大量賣血者受到病毒感染。

為了抽取最大量的血清,通常做法是將過濾了血清的血液輸回捐血者體內,今次「金銀潭醫院院長」呼籲的作法是捐血漿,這方法能抽到的血清更少。

在外國,抽血清通常由醫院或大學教學醫院進行,「中國生物技術公司」似乎未進行過「隨機對照試驗」,在我看來,這是綽頭鬧劇而已。」

後語

相關今趟病毒的局勢發展很快,文章寫出後只好用後語加註。首先,應該譴責在地鐵放破壞物的行為。從數字看,疫情似乎控制在武漢區,死亡數字沒有幾何級數上升,社區隔離做得頗嚴厲。筆者原以為社區私家醫生的生意在這段時期應該很好,實情相反,據一些家庭醫生表示,由於大部份港人在日常生活中帶了口罩,連季節性流感都減少,這些是他們的主要收入。基於此,筆者估計疫情的受控可能比一般人預計的更快。

香港的政務官很狡滑。一位退休高官在半個月前私下裏表示:「我覺得林鄭月娥故意誇大疫情,沖淡過去半年市民對她的反感,限制市民各種活動,尤其是關閉政府設施,我們交稅養一班不用工作的公務員,真是冤枉。郵局只開4小時,一定會製造大量市民排隊的場面,很多小市民要去郵局交各種費用的,小弟也要去交稅,難以控制,增加交叉感染的風險,簡直是荒謬。她拒絕封關,結果與中國大陸捆綁一起,被國際封鎖,一國兩制又受到多一次的摧殘、蹂躙!」

備註

(註一)

Could Rats be the Possible Intermediate Hosts in the 2019 Wuhan COVID-19 Outbreak?

流行病學者吳錦祥推斷 新冠肺炎罪首是武漢本地老鼠  ----世界日報

ResearchGate網上專文指出,新冠肺炎(COVID-19)的最大可疑中間宿主是老鼠,更明確的說,是武漢本地老鼠。

(註二)

輸康復者血漿 11重症病情轉好 金銀潭院長籲「過來人」捐血 專家:療法存風險

國務院國資委直管的國藥集團旗下中國生物技術公司也在當日晚宣布,已完成對部分康復者血漿的採集工作,並成功製備出用於臨床治療的特免血漿。「中國生物」在微博上稱,這是目前治療感染的最有效方法,可大幅降低重症患者死亡率。

(註三)

Immune responses to viruses

Via cytotoxic cells

When a virus infects a person (host), it invades the cells of its host in order to survive and replicate. Once inside, the cells of the immune system cannot ‘see’ the virus and therefore do not know that the host cell is infected. To overcome this, cells employ a system that allows them to show other cells what is inside them – they use molecules called class I major histocompatibility complex proteins (or MHC class I, for short) to display pieces of protein from inside the cell upon the cell surface. If the cell is infected with a virus, these pieces of peptide will include fragments of proteins made by the virus.

A special cell of the immune system called a T cell circulates looking for infections. One type of T cell is called a cytotoxic T cell because it kills cells that are infected with viruses with toxic mediators. Cytotoxic T cells have specialised proteins on their surface that help them to recognise virally-infected cells.

Viruses are highly adaptable, and have developed ways to avoid detection by T cells.  Some viruses stop MHC molecules from getting to the cell surface to display viral peptides. If this happens, the T cell doesn’t know there’s a virus inside the infected cell.

However, another immune cell specialises in killing cells that have a reduced number of MHC class I molecules on their surface – this cell is a natural killer cell or NK cell for short.  When the NK cell finds a cell displaying fewer than normal MHC molecules it releases toxic substances, in a similar way to cytotoxic T cells, which kill the virally-infected cell.

Via interferons

Virally infected cells produce and release small proteins called interferons, which play a role in immune protection against viruses. Interferons prevent replication of viruses, by directly interfering with their ability to replicate within an infected cell. They also act as signalling molecules that allow infected cells to warn nearby cells of a viral presence – this signal makes neighbouring cells increase the numbers of MHC class I molecules upon their surfaces, so that T cells surveying the area can identify and eliminate the viral infection as described above.

(註四)

“Need to introduce some basic concepts of immunity. There are two types of immunity in the body: humoral (antibodies) and cellular ( Killer cells). Antibodies are useful for extra-cellular pathogens such as bacteria by identifying them, binding to them and destroying them. Since viruses quickly enter into body cells and not circulating in blood, this type of immunity has limited usefulness.

Cellular immunity is the major defence against intercellular pathogens such as viruses by identifying infected cells and destroying them together with the virus inside. There are still antibodies formation in a viral infection but quantity is limited. In vaccines for viruses we inject viral antigens into the body which stays in the blood to provoke an antibody response. This vaccine response is much stronger than the natural infection.

In COVID-19 infection some antibodies are produced but we do not know the quantity. In any case it is very small quality overall and to harvest it you need a lot of serum which contain the antibodies. In commercial production (where we extract non specific antibodies) donated blood is separated into blood cells and serum and antibodies are then extracted from pooled sera. That’s the job of the Red Cross. The production process is very complicated and strict hygiene observed. Only a few laboratories in each country are licensed to produce antibodies (known commercially as gamma globulins). Ten over years ago in China they used a different method to extract serum antibodies. Since voluntary blood donation is very backward they hired professional donors. In order to extract as much antibodies as possible they did a kind of dialysis (plasmapheresis) in which antibodies are separated from the blood cells and collected and the blood cells are then returned to the donor in order that he can donate more serum than a regular blood donation. This was done under very poor supervision and caused a major outbreak of AIDS in Hunan 湖南愛滋村。Thousands of people were infected and died. After that the government severely limited the commercial production of gamma globulin.

In the present case the announcement was from a pharmaceutical company rather than a hospital or university. There is no evidence that they did a randomised double blinded study. Collecting blood from convalescent patients is not advisable as they may still have hidden viruses in their body. The whole thing looked like a PR scam to me. ”

發表意見