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Covid-19: Four in 10 people with evidence of past infection had no classic symptoms, study finds

BMJ 2021; 372 doi: (Published 03 February 2021) Cite this as: BMJ 2021;372:n321

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It is necessary to continuously perform detailed discussion from a lot of aspects including clinical, epidemiological, biological, immunological, and social areas due to elucidate various contents in COVID-19

Dear Editor

 A BMJ article entitled “Covid-19: Four in 10 people with evidence of past infection had no classic symptoms, study finds” by Elisabeth Mahase [1] showed the patterns of completely asymptomatic and none of the three classic symptoms of the disease. This report is precious for medical staff and researchers in particular. We consider that discussion about this content was necessary from clinical, epidemiological, biological, immunological areas. There are a lot of unknown contents in COVID-19.

 Many people are experiencing sequelae of COVID-19 regardless of whether their infection was mild or severe; these sequelae include malaise, depressed mood, brain fog, fatigue, chest tightness, alopecia, and taste disorder, among others [2]. The media have reported that many of these complaints are coming from younger people and that people may be suffering from the sequelae for a prolonged period [2]. Poor health and pessimism due to the sequelae of COVID-19 are likely to continue over the medium term and long term. A handful of facilities across Japan have begun providing outpatient care specializing in the sequelae of COVID-19. In order to establish measures for sequelae of COVID-19, medical personnel in fields such as medicine and nursing need to work with the government to promptly create a national-level system to handle the item. Therefore, clinical, epidemiological, biological, and immunological researches are important around the world in the future.

In Japan, pregnant women have been excluded from the effort obligation in the inoculation of COVID-19 vaccine [3]. A reason for the exclusion was that the data collection about the item was not enough in clinical trials [3]. The vaccine recommendation decided to be over 16 years old in Japan [3]. The contents of these items vary in each country of the world, so further clinical, epidemiological, biological, and immunological discussion are needed around the world.

 Hospitals and facilities are experiencing extreme difficulties accepting and caring for patients with dementia who have developed COVID-19 [4]. In specific terms, patients with dementia who develop COVID-19 may wander, and be unable to understand infection control measures [4]. In fact, personnel are needed for the care of patients with both dementia and COVID-19, and finding a medical facility that will accept these patients takes time. The government of one of Japan's prefectures decided to dispatch dementia specialists and care workers on a short-term basis to support medical facilities that are accepting patients with dementia and COVID-19 [5]. In the future, medical personnel specializing in psychiatry will need to further improve their ability to respond to COVID-19. This will allow psychiatric facilities to accept patients with dementia who develop COVID-19 while medical personnel specializing in psychiatry care for their physical symptoms, and it will allow more consultations with non-psychiatric departments. COVID-19 is threatening to destroy the medical system in many countries, and this disease must be dealt with through close collaboration between medical personnel in psychiatry and other departments and with further cooperation with government agencies. Hence, clinical and social discussion are urgent necessary around the world.

 The discussion of COVID-19 will be considered in medium- and long-term perspective, so it is important to be continuously studied based on diverse aspects.

Ken Inoue (1), Sadayuki Hashioka (2), Yuri Murayama (3),Yoshiyuki Ohira (4), Haruo Takeshita (2), Yasuyuki Fujita (2), Noriyuki Kawano (5)

(1) Kochi University, 2-5-1 Akebono-cho, Kochi-shi, Kochi 780-8520, Japan
(2) Shimane University, Japan
Email: (SH)
(3) Gunma University, Japan
(4) International University of Health and Welfare, School of Medicine, Japan
(5) Hiroshima University, Japan

1. Mahase E. Covid-19: Four in 10 people with evidence of past infection had no classic symptoms, study finds. BMJ 372: n321, 2021
2. NHK. Accessed 15 Feb 2021
3. San-in Chuo Shimbun. 2021; 14 Feb: 1 and 2
4. NHK. Accessed 15 Feb 2021
5. Kahoku Shimpo ONLINE NEWS. Accessed 15 Feb 2021

Competing interests: No competing interests

17 February 2021
Ken Inoue
Professor and Doctor
Sadayuki Hashioka, Yuri Murayama, Yoshiyuki Ohira, Haruo Takeshita, Yasuyuki Fujita, Noriyuki Kawano
Research and Education Faculty, Medical Sciences Cluster, Health Service Center, Kochi University, Japan
2-5-1, Akebono-cho, Kochi-shi, Kochi 780-8520, Japan