To the Editor—We are most appreciative of the communication and comments by Ng et al1 which draws our attention to the seminal works and landmark paper by Kwong et al2 in which no less than seven bacteria are listed to have significant association with colon cancer, with Clostridium septicum (hazard ratio [HR]=17.1), Gamella morbillorum (HR=15.2), and Streptococcus gallolyticus or Streptococcus bovis (HR=5.73) high on the list. Others have reported cancer association with even seemingly benign organisms such as Enterococcus faecalis or Escherichia coli.3 Conceivably, and with further validation, circulating intestinal bacteria may eventually become a new biomarker for colonic cancer especially at a pre-symptomatic stage. But here we need a word of caution. With an early doubling time of over 30 months, the early growth of a colorectal cancer has been shown to be slow.4 Early detection of a slow-growing cancer warrants other considerations. In our ageing population it is not too uncommon to see a patient in advanced age with multiple co-morbidities and limited life expectancy. In such cases further extensive investigations may not be justified. To complete the story of the patient with S gallolyticus septicaemia we barely mentioned in an earlier communication,5 he was a 91-year-old Caucasian missionary, with advanced atherosclerotic disease, severe dementia, recurrent heart failure, deteriorating renal function, and an abdominal aneurysm for which interventional treatment was rejected. The question of colonoscopy was raised but vetoed by all parties concerned. His septicaemia was successfully controlled by penicillin and his constipation well relieved by judicious enemas instead of lactulose. He lived for another 9 months, and eventually died of heart failure. From the holistic perspective, if he had an occult colonic cancer, he probably died with it, rather than of it.

The author contributed to the letter, approved the final version for publication, and takes responsibility for its accuracy and integrity.

The author has disclosed no conflict of interest.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Ng SC, Wong HK, So CK, et al. Streptococcus bovis bacteremia should be investigated for early detection of colorectal pathology. Hong Kong Med J 2019;25:414. Crossref

2. Kwong TN, Wang X, Nakatsu G, et al. Association between bacteremia from specific microbes and subsequent diagnosis of colorectal cancer. Gastroenterology 2018;155:383-90.e8. Crossref

3. Sears CL, Garrettt WS. Microbes, microbiota, and colon cancer. Cell Host Microbe 2014;15:317-28. Crossref

4. Matsui T, Yao T, Iwashita A. Natural history of early colorectal cancer. World J Surg 2000;24:1022-8. Crossref

5. Leung JSM. Streptococcal gallolyticus endocarditis—an uncommon but serious complication of constipation management. Hong Kong Med J 2019;25:257. Crossref

To the Editor—Recently, some patients have tested positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using reverse transcription polymerase chain reaction despite earlier recovery from coronavirus disease 2019 (COVID-19). Among 111 recovered patients, 5% in China and 10% in South Korea have tested positive again.1 2 Typically, after recovery from a viral infection, the body produces antibodies that can resist reinfection from the same virus.3 There is evidence that COVID-19 reinfection is not possible within 7 to 10 days.4 A Chinese study on COVID-19 involving primates showed no viral replication in all primary tissue compartments at 5 days post-reinfection, indicating that the primary infection of SARS-CoV-2 could prevent subsequent infections.5

Positive reverse transcription polymerase chain reaction test results from the patients who have recovered from COVID-19 are possibly attributed to:

(i) The virus persisting within body. Patients with severe acute respiratory syndrome have reported positive results in tests for the virus in faeces 2 months after onset.6 Respiratory tract secretion tests have also shown positive results and high concentrations of the virus for 3 weeks after onset.7 Virus shedding gradually decreases towards the detection limit around 21 days after onset.8
(ii) Cross-contamination from another betacoronavirus.9
(iii) False positive results.10
(iv) Incorrect sample collection methods. The sample may not be collected widely and deeply enough to include the virus, resulting in a negative result.11 Furthermore, the virus binds to the angiotensin-converting enzyme 2 receptor and remains in the throat, but the test includes only the upper respiratory tract where the amount of virus has been reduced.12 When clinical symptoms are stable, the virus can still spread and infect different organs such as the spleen, hilar lymph nodes, kidneys, liver, and brain; in such cases deep throat saliva test may not be able to detect SARS-CoV-2 infection.13

There is currently no supporting evidence for COVID-19 reinfection after recovery. However, it is important to ensure that samples are collected correctly and test procedures are followed properly. In accordance with the advice of the World Health Organization, patients with no clinical symptoms can be discharged from the hospital if they test negative for SARS-CoV-2 infection at least twice after a 24-hour interval.14

All authors contributed to the concept of the study, acquisition and analysis of the data, drafting of the manuscript, and critical revision of the manuscript for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

The authors have no conflicts of interest to disclose.

The authors received no funding source/grants or other materials support for this work.

1. Mystery in Wuhan: Recovered coronavirus patients test negative…then positive. 27 March 2020. Available from: https://www.npr.org/sections/goatsandsoda/2020/03/27/822407626/ mystery-in-wuhan-recovered-coronavirus-patients-test-negative-then-positive. Accessed 22 Apr 2020.

2. Over 110 people retest positive for coronavirus: authorities. 12 April 2020. Available from: http://www.koreaherald.com/view.php?ud=20200412000213&np=3&mp=1. Accessed 22 Apr 2020.

3. McCullough KC. Immune response in vitro. In: Delves PJ, Roitt IM, editors. Encyclopedia of Immunology (second edition). London: Academic Press; 1998: 1233-43. Crossref

4. Can you be re-infected after recovering from coronavirus? Here’s what we know about COVID-19 immunity. 13 April 2020. Available from: https://time.com/5810454/coronavirus-immunity-reinfection. Accessed 22 Apr 2020.

5. Bao L, Deng W, Gao H, et al. Reinfection could not occur in SARS-CoV-2 infected rhesus macaques. BioRxiv [Preprint] 2020. Available from: https://doi.org/10.1101/2020.03.13.990226. Accessed 22 Apr 2020.

6. Isakbaeva ET, Khetsuriani N, Suzanne Beard R, et al. SARS-associated coronavirus transmission, United States. Emerg Infect Dis 2004;10:225-31. Crossref

7. Chan JF, Yip CC, To KK, et al. Improved molecular diagnosis of COVID-19 by the novel, highly sensitive and specific COVID-19-RdRp/Hel real-time reverse transcription-PCR assay validated in vitro and with clinical specimens. J Clin Microbiol 2020;58:e00310-20. Crossref

8. He X, Lau EH, Wu P, et al. Temporal dynamics in viral shedding and transmissibility of COVID-19. Nat Med 2020 Apr 15. Epub ahead of print.

9. Coronaviridae Study Group of the International Committee on Taxonomy of Viruses. The species severe acute respiratory syndrome–related coronavirus: classifying 2019-nCoV and naming it SARS-CoV-2. Nat Microbiol 2020;5:536-44. Crossref

10. Lan L, Xu D, Ye G, et al. Positive RT-PCR test results in patients recovered from COVID-19. JAMA 2020 Feb 27. Epub ahead of print. Crossref

11. Yi Y, Lagniton PN, Ye S, Li E, Xu RH. COVID-19: what has been learned and to be learned about the novel coronavirus disease. Int J Biol Sci 2020;16:1753-66. Crossref

12. Jia HP, Look DC, Shi L, et al. ACE2 receptor expression and severe acute respiratory syndrome coronavirus infection depend on differentiation of human airway epithelia. J Virol 2005;79:14614-21. Crossref

13. Yao XH, Li TY, He ZC, et al. A pathological report of three COVID-19 cases by minimally invasive autopsies [in Chinese]. Zhonghua Bing Li Xue Za Zhi 2020;49:E009. Crossref

14. Coronavirus disease (COVID-19) technical guidance: Laboratory testing for 2019-nCoV in humans. 8 April 2020. Available from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/laboratory-guidance. Accessed 22 Apr 2020.

To the Editor—To date, there are no reported outbreaks of coronavirus disease 2019 (COVID-19) among traditional Chinese medicine (TCM) practitioners and their patients. Traditional Chinese medicine is popular globally, especially in Asian populations such as in Hong Kong. The concept of integrative medicine is appreciated by members of the public.1 2 Patients who do not want to be treated by Western medicine often seek TCM herbal remedies instead. Practitioners of TCM are confronted with infection control issues when they treat patients with mild and vague symptoms. Some TCM practitioners wear personal protective equipment, including mask and gown, to protect themselves during consultations. However, several routine TCM manoeuvres are high-risk. In TCM, the tongue is considered to have many relationships and connections in the body, both to the meridians and the internal organs. It is therefore considered essential and important to inspect the tongue for confirming TCM diagnoses. Pulse diagnosis also provides TCM practitioners with information about the health of their patients. In terms of treatment, many TCM procedures such as acupuncture, cupping, and moxibustion are considered high-risk. Various issues are encountered by TCM practitioners (Table3 4 5).

There are currently over 10 000 TCM practitioners in Hong Kong, compared with 14 600 doctors of Western medicine. These TCM practitioners have an important role to contribute in sharing the health burden in the current COVID-19 pandemic, at least in diagnosing and treating mild cases. The role of TCM is now well established and the dispensation, storage, and labelling of Chinese herbal medicines has been regulated since 2003. In addition, TCM practitioners are regulated and there are plans for a Chinese Medicine Hospital in Tseung Kwan O.6 Although there is ongoing research into TCM treatment of COVID-19, the role of the discipline is limited and needs deliberation and recognition.3 4 5

In mainland China, the treatment protocol for diagnosis and treatment for novel coronavirus pneumonia has confirmed the integrative role of TCM in the management of COVID-19.7 Treatment is offered based on stages of disease, namely, pre-diagnosis, confirmed (mild, moderate, severe, and critical), and rehabilitation.7 As with many treatment strategies worldwide, trials are ongoing and there has been no current evidence to support or refute many of the novel treatments, neither in Western nor TCM.

The current policy of the Hong Kong SAR government is that all cases are centralised and managed in the public Hospital Authority system, exclusive of private sector or TCM partners. It is recommended that the Hong Kong SAR government may follow the policy in mainland China to provide TCM as a complementary treatment for in-patients with milder disease as part of the healthcare team responding to COVID-19. In addition, TCM can be offered to patients in the pre-diagnosis and rehabilitation periods for health promotion. There is nothing to lose when patients and citizens see that holistic or integrative medicine is provided by the public system. When further evidence of efficacy is established, TCM can be promoted in the other TCM clinics to serve the public.

The TCM practitioners in Hong Kong have important roles in treating patients with suspected COVID-19 in the community.

All authors contributed to the concept of the study, acquisition and analysis of the data, drafting of the manuscript, and critical revision of the manuscript for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

All authors have no conflicts of interest to disclose.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Hon KL, Leung AK. Integrative, integrated medicine but no integration: Tarnishing steroid and Chinese medicine is vanity. Hong Kong J Paediatr 2018;23:192-4.

2. Hon KL, Leung AK, Leung TN, Lee VW. Complementary, alternative and integrative medicine for childhood atopic dermatitis. Recent Pat Inflamm Allergy Drug Discov 2017;11:114-24. Crossref

3. Ren JL, Zhang AH, Wang XJ. Traditional Chinese medicine for COVID-19 treatment. Pharmacol Res 2020;155:104743. Crossref

4. Chan KW, Wong VT, Tang SC. COVID-19: An update on the epidemiological, clinical, preventive and therapeutic evidence and guidelines of integrative Chinese-Western medicine for the management of 2019 novel coronavirus disease. Am J Chin Med 2020;48:737-62. Crossref

5. Gray PE, Belessis Y. The use of Traditional Chinese Medicines to treat SARS-CoV-2 may cause more harm than good. Pharmacol Res 2020;156:104776. Crossref

6. Hong Kong SAR government. Prequalification for operation of Chinese Medicine Hospital in Tseung Kwan O (with video). 13 September 2019. Available from: https://www. info.gov.hk/gia/general/201909/13/P2019091200691.htm. Accessed 4 May 2020.

7. National Health Commission & State Administration of Traditional Chinese Medicine. Diagnosis and treatment protocol for novel coronavirus pneumonia; 2020. Available from: https://www.chinadaily.com.cn/pdf/2020/1.Clinical. Protocols.for.the.Diagnosis.and.Treatment.of.COVID-19. V7.pdf. Accessed 4 May 2020.

To the Editor—Two recent articles concerning corticosteroid usage in the coronavirus disease 2019 (COVID-19) pandemic provide opposing evidence and run the risk of muddying the waters on this controversial yet important topic.1 2 On the one hand, Russell et al1 tabulated a number of mainly observational clinical studies cautioning more harm than benefit with corticosteroid usage. On the other hand, Shang et al,2 acknowledging that existing evidence is inconclusive at best, referenced recommendations by Chinese physicians with frontline clinical experiences of COVID-19 who advocate short courses of corticosteroids at low-to-moderate doses for more severe disease.

In clinical settings, physicians tend to use corticosteroids only for treating critically ill patients. Therefore, selection bias and confounders in observational studies might contribute to any observed increased mortality in patient groups treated with corticosteroids. The papers cited by Russell et al1 omit to address coronavirus mortality, and the strength of the evidence presented does not support the certainty of the authors’ conclusions (Table).

Similar to respiratory viral diseases such as the seasonal influenza, two categories of people seem susceptible to die from COVID-19: older adults, especially those with chronic disease or other co-morbidities, and seemingly healthy adults with exacerbated autoinflammatory syndrome termed the cytokine storm syndromes.3 4 5 On the contrary, children and infants seem to survive epidemics of coronavirus infections with very mild disease.6

We acknowledge the potential risks associated with high-dose corticosteroids in treating COVID-19 pneumonia, and agree that corticosteroid usage should be avoided if there are other efficacious anti-inflammatory immunomodulating medications against the cytokine storm, such as intravenous immunoglobulin, interleukin-1 inhibitors, interleukin-6 inhibitors, and Janus kinase inhibitors.4 However, on the basis of recommendations by frontline Chinese physicians and local clinical experience during the severe acute respiratory syndrome epidemic, a short course of corticosteroids at low-to-moderate dose is probably justifiable for critically ill patients with hyperinflammation.7 8 Chinese researchers are running a prospective randomised controlled trial to review the efficacy and safety of corticosteroids.9 Until further evidence becomes available, whether to use corticosteroids or not remains controversial.

All authors contributed to the concept of the study, acquisition and analysis of the data, drafting of the manuscript, and critical revision of the manuscript for important intellectual content. All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

The authors have no conflicts of interest to disclose.

This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

1. Russell CD, Millar JE, Baillie JK. Clinical evidence does not support corticosteroid treatment for 2019-nCoV lung injury. Lancet 2020;395:473-5. Crossref

2. Shang L, Zhao J, Hu Y, Du R, Cao B. On the use of corticosteroids for 2019-nCoV pneumonia. Lancet 2020;395:683-4. Crossref

3. Novel Coronavirus Pneumonia Emergency Response Epidemiology Team. The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) in China [in Chinese]. Zhonghua Liu Xing Bing Xue Za Zhi 2020;41:145-51.

4. Mehta P, McAuley DF, Brown M, Sanchez E, Tattersall RS, Manson JJ, et al. COVID-19: consider cytokine storm syndromes and immunosuppression. Lancet 2020;395:1033-4. Crossref

5. Ng PC, Lam CW, Li AM, Wong CK, Cheng FW, Leung TF, et al. Inflammatory cytokine profile in children with severe acute respiratory syndrome. Pediatrics 2004;113:e7-14. Crossref

6. Hon KL, Leung CW, Cheng WT, Chan PK, Chu WC, Kwan YW, et al. Clinical presentations and outcome of severe acute respiratory syndrome in children. Lancet 2003;361:1701-3. Crossref

7. Zhao JP, Hu Y, Du RH, Chen ZS, Jin Y, Zhou M, et al. Expert consensus on the use of corticosteroid in patients with 2019-nCoV pneumonia [in Chinese]. Zhonghua Jie He He Hu Xi Za Zhi 2020;43:183-4.

8. Yam LY, Lau AC, Lai FY, Shung E, Chan J, Wong V, et al. Corticosteroid treatment of severe acute respiratory syndrome in Hong Kong. J Infect 2007;54:28-39. Crossref

9. US National Library of Medicine, US Government. Efficacy and Safety of Corticosteroids in COVID-19. Available from: https://clinicaltrials.gov/ct2/show/NCT04273321. Accessed 24 Mar 2020.