Ten commonly asked questions about Covid-19 and lessons learned from Thailand

Purpose – As the world faces a new health crisis threatening people with the spread of Covid-19, this study aims to summarize the key information of Covid-19 related to disease characteristics, diagnosis, treatment and prevention along with the lessons learned from Thailand. Design/methodology/approach – The narrative review was synthesized from various sources such as the World Health Organization; Centers for Disease Control and Prevention; Ministry of Public Health and other related news; articles in ScienceDirect, PubMed, Google Scholar; and the author ’ s perspective regarding the lessons learned from Thailand with keywords of “ Covid-19 ” and “ Coronavirus ” from January to August 2020. Google Trends was used to set common questions. Findings – Covid-19 is the seventh family of coronaviruses that cause various symptoms related to respiratory systems. The disease can be treated through general and symptomatic treatment, by using antiviral drugs. As of July 2020, there are four potential vaccine candidates ChAdOx1 nCoV-19, mRNA-1273, Ad5-nCOVandBNT162b1.TherecommendationsforCovid-19preventionarephysicaldistancing,facemasks,eyeprotectionandhandwashing.Thailandisnowconsideredaslow-riskforCovid-19possiblybecauseof(1)softpolicybygovernmentactions,(2)villagehealthvolunteers,(3)integrationoftechnologyand(4)fact-basedcommunications. Originality/value – This study summarized the key points about Covid-19, clarified some misunderstandings and shared strategic actions from Thailand, which can be adapted according to the different capacities and situations in other countries.

showed two major types of the virus as L type (70%; more prevalent, more aggressive and spread more quickly) and S type (30%; less aggressive and evolution older) [2,3].

How was Covid-19 originated?
In December 2019, there was a group of acute respiratory illness patients with unknown causes, now known as Covid-19, that occurred in a seafood wholesale market in Wuhan, Hubei Province, China. Then, the outbreak of Covid-19 spread rapidly from Wuhan to other areas and different countries. At present (as of August 2020), the WHO reported that the confirmed Covid-19 cases spread to all regions such as Americans, Europe, South-East Asia, Eastern Mediterranean, Africa and Western Pacific [5]. The origin of Covid-19 was still inspected, and the current evidence identified that the spread to humans potentially occurred through transmission from wild animals sold in the Huanan Seafood Wholesale Market [6].
According to the clinical manifestations, Covid-19 symptoms can be grouped based on the severity of illness as follows [10].

Asymptomatic or pre-symptomatic infection
Individuals who test positive for SARS-CoV-2 by virologic testing using a molecular diagnostic (e.g. polymerase chain reaction -PCR) or an antigen test, but the absence of clinical signs and symptoms with normal chest or CT scan.

Mild illness
Individuals who have any of the various signs and symptoms of Covid-19 (e.g. fever, chills, muscle pain, runny nose, cough, sore throat, headache and loss of taste or smell, nausea, vomiting, abdominal pain and diarrheas) and normal pulmonary clinical exam without pneumonia or breathing difficulties and dyspnea.

Moderate illness
Individuals who have evidence of lower respiratory tract disease by clinical exam or imaging with chest CT scan will show typically pulmonary lesions and saturation of oxygen (SaO 2 ) ≥ 94% on room air at sea level.

Severe illness
Individuals whose clinical symptoms deteriorate and usually occur in a week with the development of dyspnea and hypoxemia, have respiratory frequency > 30 breaths per minute, blood oxygen saturation (SaO 2 ) < 94% on room air at sea level, a ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO 2 /FiO 2 ) < 300 mmHg or lung infiltrates > 50%.

Critical illness
Individuals whose symptoms rapidly deteriorate to respiratory failure and present septic shock, encephalopathy, myocardial injury or heart failure, coagulopathy and/or multiple organ dysfunction.

What is the incubation period and the transmission of Covid-19? And, how is Covid-19 diagnosed?
Many studies [8,11,12] reported the mean incubation period of Covid-19 to be about 4-6 days with many weeks to die or recover. The study [13] estimated 14 days or more to develop symptoms. Interestingly, one study identified the four stages of evolution on chest CT scans among patients with Covid-19 from symptom onset; early-stage (0-4 days), progressive stage (5-8 days), peak stage (9-13 days) and absorption stage (more than 14 days) [12].
According to the potential transmission route of Covid-19, it started from SARS-like bat viruses as the primary reservoir and the consumption of those infected animals as food by humans was the beginning of the animal to human transmission. However, the intermediate source is still unknown [14]. Recently, the report confirmed the rapid transmission from human to human [15].
Covid-19 can spread through both direct and indirect contact. Direct contact is the source of Covid-19 transmission through touching mouth, nose or eyes with contaminated fingers.

Covid-19
Indirect contact, such as contaminated objects, respiratory droplets and airborne contagion, is also another source of Covid-19 transmission.
For droplet transmission, viral particles (saliva or mucous droplets) in the droplets can spread during coughing, sneezing, laughing, singing, breathing and talking. Droplets typically cannot transverse more than 6 ft or about 2 m, and they cannot stay alive in the air for a long time [4]. Interestingly, the droplets remain on the surfaces of inanimate objects to produce a thin film of the virus. Depending on the types of the object surface, the virus resides on fomites in the environment for hours and days [16]. Half-lives of Covid-19 (hours) estimation in various surfaces and aerosol were (1) polypropylene (plastic) 15.9, (2) stainless steel 13.1, (3) cardboard 8.45, (4) copper 3.4 and (5) aerosol 2.74. The transmission of Covid-19 can occur from the contaminated surface to the hands of the people who touch the surface subsequently and then touches his or her own mucous membrane (mouth, nose or eyes).
For airborne transmission, Covid-19 can stay intact and contagious in droplets (less than 5 μm in diameter) and can survive in the air for up to 3 h [16]. This evidence indicated the viable and infectious form of Covid-19 involved airborne transmission. Also, two studies supported the assumption of airborne transmission through small particles with viral content might travel in indoor environments, covering distances up to 10 m, starting from the emission sources [17,18]. Therefore, all of these conclusions about the airborne transmission of Covid-19 in indoor environments, especially in crowded, poorly ventilated environments were in line with many previous studies [19][20][21].
Covid-19 infection is diagnosed by finding evidence of the virus from the respiratory tract system. There are three types of tests available for Covid-19 as follows [22,23]: (1) PCR test: This test looks for pieces of the virus that causes Covid-19 from the nose, throat or other possible areas in the respiratory tract to identify if the person has an active infection. This test provides the results for longer than the antigen test and antibody test. This test is typically highly accurate and usually does not need to be repeated.
(2) Antigen test: This test looks for pieces of proteins that make up the virus that causes Covid-19 to detect if the person has an active infection. Samples will be collected from a nasal or throat swab. This test provides results faster than the PCR test. Positive results from the antigen test are usually highly accurate, but negative results may need to be confirmed with a PCR test.
(3) Antibody (serology) test: This test looks for antibodies against the virus that causes Covid-19 in the blood to determine if there was a past infection, but it should not be used to diagnose an active infection. Samples will be collected from blood, and the test provides quick results. This test detects the antibodies and not the virus, so it might take several days or weeks for the body to develop enough antibodies to be detected.

What is the current situation of Covid-19?
According to a WHO report [5] 6. Is it true that Covid-9 is likely to attack old people? Covid-19 is more likely to attack older men or women with comorbidities and can even cause death for those with severe respiratory diseases [8]. Based on the mechanism of action of Covid-19, the studies reported that the angiotensin-converting enzyme 2 (ACE2) has been identified as the cellular receptor for Covid-19. ACE2 is normally expressed on type I and type II alveolar epithelial cells of human epithelia of the lung and small intestine. The binding of Covid-19 to ACE2 results in an additional expression of ACE2, which can cause alveolar cell damage. It has also been found that the receptor binding ability of Covid-19 is 10 to 20 times stronger than that of SARS-CoV [24]. However, younger people with obesity can shift to severe Covid-19 disease. As obesity will interfere with respiratory function and restrict ventilation by obstructing diaphragm excursion, it impairs immune responses to viral infection, is pro-inflammatory and induces diabetes and oxidant stress to adversely affect the cardiovascular system [25]. Based on one study [26], it is reported that Covid-19 in the child population usually causes mild symptoms with fever or no fever, cough, fatigue, diarrhea, vomiting or abdominal distension. However, Covid-19 in children has a good prognosis, and most cases recovered after those mild symptoms. It can be explained by (1) the distribution of ACE2 receptors (lower binding capacity) in children's lung tissues is different from adult lung tissues [26,27]; (2) children experienced exposure to other respiratory viruses such as respiratory syncytial virus, Influenza A, and Influenza B viruses, which potentially induce their serum antibody levels and could provide cross-protection [28]; (3) children's immune system is not fully mature, so the immune system of children does not respond in the same way as an adult's response [28].
7. Is the alcohol-based hand rub solution efficient enough to prevent Covid-19 from spreading? The WHO and Centers for Disease Control and Prevention (CDC) suggested the prevention of Covid-19 by using soap with water for at least 20 s, or ethanol alcohol with at least 60% alcohol, especially after being in a public area or after coughing and sneezing [29,30]. One study [31] experimented with WHO's two alcohol-based formulations for hand sanitization from "Guidelines on Hand Hygiene in Health Care" to reduce pathogen infection and spreading. Formulation I was 85% ethanol (v/v), 0.725% glycerol (v/v) and 0.125% hydrogen peroxide (v/v). Formulation II was 75% isopropanol (w/w), 0.725% glycerol (v/v) and 0.125% hydrogen peroxide (v/v). The study also tested the effect of ethanol and isopropanol on Covid-19.
The study [31] reported that both WHO formulations can be effective for de-activating Covid-19 and recommended it to be used in health-care systems and in a viral outbreak situation. Also, both tested alcohols, ethanol and isopropanol, with a minimal final concentration of at least 30% can de-activate the virus in 30 s. Therefore, alcohol-based hand rub products used in health care with at least a minimum alcohol concentration of 30% is powerful enough to get rid of Covid-19. However, frequent hand wash over all surfaces of hands with water and soap or alcohol is still required. "Face masks and eye protection": The use of face masks such as N95 respirators, surgical masks and eye protection has provided protection for health-care staff and people in the community. For health-care staff and administrators, N95 respirators offer more protection from Covid-19 transmission than surgical masks. Non-medical or clothing masks are essential to prevent contaminating infected people when they sneeze or cough. Non-medical masks might be made of different combinations of fabrics and materials, multi-layering sequences so the selection of clothing masks is very important. Moreover, the use of clothing masks also prevents the unnecessary use and shortage of surgical masks and N95 respirators, which are crucial for health-care workers in hospital settings. At present, everybody should wear face coverings in public to prevent the spread of Covid-19 because asymptomatic Covid-19 patients can still spread the virus.
(2) "Hand washing": Hand hygiene practice is recommended for all health-care workers and general people of all ages. Regular and thorough use of soap with water for washing at least 20 s, or alcohol-based hand rub, especially after having been in a public area and after coughing, or sneezing and before eating, touching eyes, nose and mouth is recommended. It is also important to avoid touching the facial T-zone (eyes, nose, and mouth) because this is the access point for the virus to get into the upper respiratory tract.  [44]. At first, Thailand began screening passengers traveling from Wuhan by checking their temperatures at local and international airports. On January 13, 2020, the imported first case of Covid-19 was a 61-year-old Chinese woman from Wuhan City. Then, the first Thai citizen with Covid-19 and a travel history to Wuhan was found on January 23, 2020. As a result, Thailand strictly screened people who worked closely with or were in frequent contact with Chinese people such as tour guides, hotel staff, taxi drivers and airport staff. On January 31, 2020, the first identified Thai case human-to-human of Covid-19 was a taxi driver. On February 29, 2020, the MOPH announced Covid-19 as a dangerous communicable Disease Act, B.E. 2558 (A.D.2015) [44]. On March 26, 2020, the number of Covid-19 cases rose dramatically and exceeded more than 1,000 cases. On April 2, 2020, the Thai government announced a curfew between 10.00 p.m. to 4.00 a.m. throughout the Kingdom of Thailand. The Civil Aviation Authority of Thailand (CAAT) also announced that all international passenger flights were banned from entering Thailand [45]. From April 27 to August 2020, the number of new Covid-19 cases declined, with the most Covid-19 cases coming from outside Thailand with state quarantine, as shown in Figure 1. Meanwhile, the Thai government also gradually announced easing lockdown restrictions step by step. Today, Thailand has become one of the lowest-risk countries for Covid-19 and has been described as an example of a country that successfully fought against Covid-19's spread. However, there are challenges for Thailand after foreign tourists begin returning to Thailand. Two previous studies [46,47] indicated that the movement between Thai people and foreign tourists along with generated income from tourist activities play an important role in the spread of Covid-19 Note(s): Data from https://ddc.moph.go.th/viralpneumonia/eng/index.php Time Figure 1. New Covid-19 patient's rate in Thailand from January to August 2020 [48] Covid-19 in Thailand. This is in line with the information over the past few months (until August 2020) where new cases of Covid-19 were still found only in the state quarantines. As a result, all passengers who arrived from other countries had to be screened for Covid-19 and followed by 14 days in quarantine according to MOPH's regulations. The possible reasons for the success of Thailand against the Covid-19 pandemic as follows.
(1) "Soft policy by government actions": Although the government announced the state of emergency and a curfew during the night (10.00 p.m.-4 a.m.), the essential health and living services such as hospitals, drug stores, supermarkets and takeout places were allowed to function. In Bangkok, public transportations such as buses, the light rail and the subway continued to operate. However, after the cases started declining along with continued careful monitoring, the Thai government also gradually relaxed the lockdown (from Phase 1 to Phase 5) through the announcement of the Center for Covid-19 Situation Administration (CCSA). The social distancing policy was also promoted during the easing of the lockdown relaxation. As a result, Thai people who suffered from the economic situation during Covid-19 could restore their businesses but had to strictly follow the Covid-19 prevention guidelines laid out by the government.
(2) "Village health volunteers (VHV)": VHV was the foundation of primary health care for the sustainability of the health-care system in Thailand. It was built under the concept of "community participation" related to public health promotion strategies and the selection of village health volunteers based on their willingness to do good deeds and have sufficient health-care knowledge. As a result, VHVs have a strong relationship and bond with health-care workers and some also have a close connection with community leaders [49,50]. One VHV is responsible for 15 households, and thus, one province has approximately 20,000-30,000 VHVs. In short, there are approximately 80,000-100,000 VHVs across Thailand [50]. Currently, Thailand has approximately 1.4 million public health volunteers working alongside the health-promoting hospitals. Since the establishment of the VHV initiative 40 years ago in 1977, there are now VHVs in almost every village. These volunteers performed many tasks such as health survey, data collection and disease prevention campaigns. During the Covid-19 pandemic, health volunteers have cooperated with the Thai government policy and worked hard to prevent the spread of Covid-19. They also take care of a community member's health and improve their daily hygiene. The MOPH also provided guidelines for volunteers on how to protect themselves against Covid-19 and taught them how to make their own protective masks and hand sanitizers. Following these guidelines, health volunteers can pass on this knowledge to their families and community members. The VHVs work efficiently, knocking from door to door on at least 12 million doors to identify those at risk of contracting Covid-19 [51].
(3) "Integration of technology in health-care system" This is a collaboration between public and private sectors for controlling the spread of Covid-19 in Thailand.
Regarding the VHVs, the deputy minister of Public Health signed a memorandum of understanding (MOU) between the Health Service Support Department and Advance Info Service (AIS) to provide health news for VHVs via a mobile application called "Aor Sor Mor Online" [52,53]. The application was introduced in 2015. In the beginning, public health staff and health volunteers were the main users because both groups worked closely together for the sustainability of health-care systems in Thailand. This application can serve many functions such as reporting infectious disease cases and volunteer works, getting news, messaging and making appointments. Additionally, users can share useful information represented in the form of texts, images, audio, video and locations, as shown in Figure 2.
During the Covid-19 pandemic, VHVs use Aor Sor Mor Online to update the situation in their responsible areas, record the data from people who came back from risky countries, educate the community and follow-up on quarantine. This application also supports the readiness for the tasks of VHVs for lists of Covid-19 risky counties based on the database of the department of disease control, MOPH, knowledge about Covid-19, prevention and surveillance mechanism in the responsible area. Meanwhile, VHVs work with community leaders, networks, officers to prepare the readiness to fight against Covid-19 along with self-screening or self-checkup before going on the field to visit community or households equipped with facial masks, thermometers, alcohol gel, stickers for households that are being screened and educational materials about Covid-19 for public and equipment bags. Another application for Covid-19 called "Thai Chana Application" is shown in Figure 3 along with 24 call centers at 1119: On May 15, 2020, the Thai Chana application, developed by the Ministry of Digital Economy and Society, was implemented for contact tracing and informing the public of risks. As of May 17, 2020, 2,002,897 million people used the Thai Chana platform with individuals scanning QR codes when entering the outlets 2.66 million check-ins at registered shops, and 1.85 million check-outs. The results showed good cooperation from business establishments and the public. The CCSA encouraged the public to use and download the "Thai Chana" application. The CCSA reiterated that data and information from this platform would be used by the Department of Disease Control and MOPH for a limited period and for contact tracing and treatment only [54].
(4) "Fact-based communications and centralized structure by the prime minister": Although Thailand set up the EOC on January 4, 2020, the agencies within the EOC still lack coordination. As a result, on March 27, 2020, the Thai government announced the establishment of a CCSA led by the prime minister, which centralized the structure of the organization appropriate for the performance and tasks. As a result, the enforcement and implementation from both central and local government regulation move forward in the same direction. Meanwhile, in the current Covid-19 situation, there is a lot of fake news and incorrect information that causes confusion, fear and distrust among the public. As a result, the CCSA appointed spokespersons with a medical background to provide updates on the Covid-19 situation and create awareness of Covid-19 prevention. If managed with sincerity, good manners, and focus on effective communication, it can generate public trust in the spokespersons' daily briefings and also in the Thai government's efforts as well.

Conclusion
The profiles of Covid-19 are dynamic and rapidly evolving. Some information is still under investigation. The study has limitations in terms of comparison of Thailand