The virus is thought to be natural and has an animal origin through spillover infection. There are a plenty of coronaviruses, most of which circulate among animals including pigs, camels, bats, and cats. Sometimes these viruses jump to humans—a spill over event—and can cause disease, as happened with Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and now COVID-19. The virus originated in bats and was transmitted to humans through yet unknown intermediary animals in Wuhan, Hubei province, China in December 2019. The symptoms are usually fever, cough, sore throat, breathlessness, fatigue, malaise among others. The disease is mild in most people; in some (usually the elderly), it may progress to pneumonia, acute respiratory distress syndrome (ARDS) and multi organ dysfunction. Many people are asymptomatic.

Corona virus disease (COVID-19) is a pandemic infectious disease caused by severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) [1]. Corona virus was first identified in December, 2019, Wuhan, China [2]. Coronaviruses are found in avian and mammalian species. They resemble each other in chemical structure &morphology: for example, the coronaviruses of humans and cattle are antigenically related [3]. The first member of the coronavirus family was discovered in the early 1930’s [4]. As of October 2020, more than 7.49 million cases of COVID-19 have been reported. More than 3.7 million people have recovered [5].

On 31st December, 2019 many viral pneumonial cases were reported with unknown cause in Wuhan, Hubei Province, China [6-7].Most of the cases had a same exposure to the Huanan wholesale sea food Market, which is much popular in trading live animals.The respiratory samples of the affected patients were sent to reference labs for investigation. On 31st December, 2019 China reported the outbreak to the WHO (World Health Organization).The Huanan sea food market was closed on 1st January [8]. WHO declared the outbreak a Public Health Emergency of International Concern (PHEIC)—7,818 cases confirmed globally; affecting 19 countries in five WHO regions on 30 January [9-10].The virus is thought to be Zoonotic origin [11]. Official publications from the WHO reported that the earliest onset of symptoms as 8 December 2019 [12]. On January 7th the cause was known and is identified as Corona Virus, which has more than 95% of the similarities with the Bat Corona Virus and more than 70% of the similarities with the SARS CoV [6-7]. The spread of Virus was almost by human-to-human transmission [13-14], the number of cases increased exponentially where the people who has no contact with Huanan Market tested positive through man to man transmission [15] .The first death case was reported on 11th Jan 2020. While in this period, cases in other countries gradually increased and were reported in people who returned from Wuhan. Gradually by 20th Jan, 2020, the health care workers were tested positive when they were treating the infected patients. The 11 million population of Wuhan was placed under lock down with no entry and exit from the city, very soon this lock down was extended to other cities of China by 23rd January, 2020. Airports in different countries along with India, has set up screening mechanism to detect Symptomatic people returning from China and put them under isolation for 14 days to test the virus [16].

​

Structure: Coronaviruses are large, roughly spherical, particles with bulbous surface projections [17]. Covid-19 size ranges from 80 to 120 nm and possess a 5' capped, single-strand positive sense RNA genome, with a length between 26.2 and 31.7 kb, the longest amongst all RNA viruses. The genome is composed of 6-10 open reading frames. Coronaviruses are classified in four different genera, alpha-, beta-, gamma-, and delta-CoV historically based on serological analysis and now on genetic studies [18-19].

The average diameter of the virus particle is around 125nm. The diameter of the envelope is 85nm and the spikes are 20nm long [20-21].The viral envelope is a lipid bilayer in which the Membrane(M), Spike(S) structural proteins , Envelope(E) are anchored [22].

In the lipid layer the ratio of E: M: S is 1:20:300 [23]. On an average a Corona virus particle has 74 spikes on the surface [24]. The surface spikes of corona virus are homotrimers of the S protein, which is composed of an S1 and S2 subunit.The homotrimeric S protein is a Class I fusion protein which involves in the Receptor Binding and Membrane Fusion between the Host cell and Virus. The S1 subunit forms the head of the spike and the S2 subunit forms the stem. The Envelope and the Membrane protein are important in forming viral envelope and also maintaining its Structure shape [25].

Figure 1: Structure of Corona Virus

According to an analysis of 103 cases, 2 strains of the new corona viruses are spreading around the world i.e., L strain and S strain. The team from the Peking University in Beijing reported 2 types of virus strains and found common mutations at two locations on the genome :72 were considered to be the “L-type” and 29 were classed “S-type”.

L-type is more prevalent and it is “more aggressive” than the S-type.

A separate analysis by the team suggests that the L-type was derived from the older S-type. The first strain is likely to have emerged around the time the virus jumped from animals to humans. The second emerged soon after that, says the team. Both are involved in the virus outbreak [26].

Mechanism of COVID-19: Coronaviruses like COVID-19 infect human cells as follows:

SARS-CoV-2 spike (S) glycoprotein binds to the cell membrane protein angiotensin-converting enzyme 2 (ACE2) to enter human cells.COVID-19 has been shown to bind to ACE2 via the S protein on its surface. The S protein is cleaved into subunits, S1 and S2 during infection .S1 contains the receptor binding domain (RBD) which allows coronaviruses to directly bind to the peptidase domain (PD) of ACE2. S2 then likely plays a role in membrane fusion.

Chinese researchers have now used cryogenic electron microscopy (cryo-EM) to study the structure of the ACE2 when it is bound to one of its typical ligands, the amino acid transporter B0AT1 and also how the COVID-19 RBD may bind to the ACE2-B0AT1 complex. These structures have previously not been identified and could aid in producing antivirals or a vaccine that can block coronavirus infection by targeting ACE2.ACE2 needs to dimerise to be active. The resultant homodimer has two PDs, able to bind to two COVID-19 S protein trimers simultaneously. A previous study found COVID-19 S proteins form trimers with two of the RBDs facing one direction (down) and the other facing the opposite way (up) [27].

​

The Incubation period of Covid-19 usually ranges from 1 to 14 days and is most commonly 5 days [28-29]. While some infected persons have no symptoms and are called Asymptomatic or Presystematic carriers [30]. Common symptoms of Covid-19 include Fever, Cough, Fatigue, Loss of appetite, shortness of breath, sputum production & muscle and joint pains [31-33].Other common symptoms include sneezing, runny nose, sore throat, diarrhoea [34].

Figure 2: Symptoms of Covid-19
Other Emergency symptoms include difficulty in breathing, persistent chest pain, sudden confusion, and bluish face or lips [35]. If the Corona virus persists for longer time it may develop complications like Pneumonia, Sepsis, Septic shock, acute respiratory distress syndrome and Kidney failure [36].

Viral Transmission & Spread

Covid-19 spreads between people more efficiently when they are in close contact with a distance of (two metres or six feet) mostly via small droplets produced while coughing, sneezing or talking [37-39]. Droplets exhaled from the infected person reach the lungs of non-infected person and settle there and cause the infection [40]. The droplets are relatively heavy and do not travel far through the air instead they fall to the surfaces.When the contaminated virus falls on the surface or floor the amount of active virus decreases with time [39-40].
If the people touch those contaminated areas and then touch their eyes, mouth, nose without washibng their hands then he is supposed to get infected [37]. Saliva and sputum carries major amounts of the virus [40]. Corona virus is not a sexually transmitted infection, it can transmit via intimate contact, kissing, faecal and oral routes [41-42]. 

Figure 3: Covid-19 transmission through droplets

Figure 4: Covid- 19 spread

Diagnosis Laboratory Testing
WHO has released several testing protocols to diagnose the Covid-19 [43]. Real-time reverse transcription polymerase chain reaction (rRT-PCR) is the standard method of testing Corona virus, which is done on Respiratory samples obtained by a nasopharyngeal swab and this test shows quick result within a few hours to two days [44-48]. A study reported that the hospitalised COVID 19 patients are asked to cough into a sterile container and then collecting a saliva sample and detected the virus in eleven of twelve patients using RT-PCR [40].

Figure 5: Demonstration of Nasopharyngeal swab
Imaging
Chest CT Scans are also helpful to diagnose the disease. Bilateral multilobular ground-glass opacities with a peripheral, asymmetric and posterior distribution are common in early infection [49]. Subpleural Subpleural dominance, crazy paving and consolidation may appear as the disease progress [50].
 

Figure 6: A CT scan of a person with COVID 19 shows light patches in the lungs

Pathophysiology
The organs which are mostly affected by the Covid-19 are the Lungs because the virus access the host cells via Angiotensin converting Enzyme 2which is abundant mostly in Type II alveolar cells of the Lungs [51]. SARS-CoV-2 may also cause respiratory failure through affecting the brainstem as other coronaviruses have been found to invade the central nervous system (CNS). [52]. Covid-19 can also cause acute myocardial injury and the cardiovascular system damage [53].A high incidence of Thrombosis and Thromboembolism is observed in ICU patients with corona infections [54].
The common cause of death in covid-19 affected patient’s complications related to Kidneys [55].
Autopsies of people who died of Corona infections have revealed lymphocyte-containing inflammatory infiltrates within the lung & diffuse alveolar damage (DAD) [56].

Prevention
Since there are no treatments for the disease, prevention is very Crucial [57]. The strategies for preventing transmission of the disease include Washing Hands, to keep the surface clean, Face masks, Maintain social distancing, Self isolation.

Figure 7: Safety Precautions
To prevent the disease, hand washing is recommended. The Centers for Disease Control and Prevention (CDC) recommends that people wash hands often with soap and water for at least 20 seconds, especially after going to toilet, before eating, after coughing, sneezing, blowing one’s nose etc., [58]. CDC also recommends using an Alcohol based Sanitizer with atleast 60% alcohol by volume [59].The WHO advised people to avoid touching their eyes, nose and mouth without washing properly [60-61].
Surface Cleaning
Surfaces must be decontaminated with a number of solutions, including Ethanol (62-71%), Isopropanol, sodium hypochlorite, hydrogen peroxide etc.,
Benzalkonium chloride and chlorhexidine gluconate are less effective [62].CDC recommends if a Covid-19 case is suspected at an Office or Home all areas should be disinfected properly to prevent virus transmission [63].

Figure 8: Face Masks
Face Masks
Face masks do not completely cure the virus but they act as Safety measure to prevent droplet transmission from one person to another person. Surgical masks are probably recommended for infected patients to minimize the travel distance of Droplets while talking,coughing,sneezing [64].

Figure 9: Social Distancing
Social distancing also called as Physical distancing is mainly employed to control viral infection and to slow the spread of virus by minimizing contact with the individuals.
Social distancing can be achieved by various methods like quarantine, journey restrictions, closing of schools, workplaces, theatres, stadiums, shopping centres etc, Individuals Can Also Employ Social Distancing Methods By Self Isolation I.E, Staying At Home, Avoid Travel And Crowded Areas [65-67].

Figure 10: Self Isolation
 

Self-Isolation 
Self-isolation is recommended for those who are diagnosed with Covid-19 and those who suspect that they are infected .Those who has been exposed to a Covid-19 patient and those who travelled to other countries are kept at isolation for atleast 14 days [68-70].
 

Treatment
Currently no medication is available to treat Corona virus disease and no cure is available till date. Antibiotics are not effective against viral infections. Researches are still going on to make a Vaccine which can eradicate Corona virus.
The U.S. Food and Drug Administration have granted permission to use other medicines to treat Corona virus as there are no options available. Two malarial drugs- Hydroxychloroquine and Chloroquine and an Antiviral drug- Remdesivir were approved to treat Corona virus. [71].

This new Corona virus pandemic outbreak has challenged the Medical, Economic, Educational and Public health infrastructure of various Countries. Time alone will tell how the virus will impact our lives here in India. More so, future outbreaks of viruses and pathogens of zoonotic origin are likely to continue. Therefore, apart from curbing this outbreak, efforts should be made to devise comprehensive measures to prevent future outbreaks of zoonotic origin.

1. "Coronavirus disease 2019 (COVID-19)—Symptoms and causes". Mayo Clinic. Retrieved 14 April 2020.

2. Wang C, Horby PW, Hayden FG, Gao GF. A novel coronavirus outbreak of global health concern. Lancet. 2020. https://doi.org/10.1016/S0140-6736 (20)30185-9.

3. Textbook of Medical MicroBiology NCBI Bookshelf.

4. INFECTION OF THE CLOACA WITH THE VIRUS OF INFECTIOUS BRONCHITIS

5. "COVID-19 Dashboard by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University (JHU)". ArcGIS. Johns Hopkins University. Retrieved 17 May 2020.

6. "Novel Coronavirus". World Health Organization (WHO). Archived from the original on 2 February 2020. Retrieved 6 February 2020.

7. "27 cases of viral pneumonia reported in central China's Wuhan City". news.cgtn.com. Retrieved 19 April 2020.

8. Xinhua. China’s CDC detects a large number of new coronaviruses in the South China seafood market in Wuhan. Available at: https://www.xinhuanet.com/202001/27/c_1125504355.htm. Accessed 20Feb 2020

9. WHO Report (30 January 2020). "Novel Coronavirus(2019-nCoV): Situation Report-10" (PDF). World Health Organization (WHO). 30 January 2020. Retrieved 30 January 2020.

10. "Statement on the second meeting of the International Health Regulations (2005) Emergency Committee regarding the outbreak of novel coronavirus (2019-nCoV)". World Health Organization (WHO). 30 January 2020. Retrieved 30 January 2020.

11. Novel Coronavirus Pneumonia Emergency Response Epidemiology Team (February 2020). "[The epidemiological characteristics of an outbreak of 2019 novel coronavirus diseases (COVID-19) in China]". Zhonghua Liu Xing Bing Xue Za Zhi = Zhonghua Liuxingbingxue Zazhi (in Chinese). 41 (2): 145–151.

12. Novel Coronavirus—China". World Health Organization (WHO). 12 January 2020.

13. Yanping Z, et al. (The Novel Coronavirus Pneumonia Emergency Response Epidemiology Team) (17 February 2020). "The Epidemiological Characteristics of an Outbreak of 2019 Novel Coronavirus Diseases (COVID-19)—China, 2020". China CDC Weekly. Chinese Center for Disease Control and Prevention. 2 (8): 113–122. Archived from the original on 19 February 2020. Retrieved 18 March 2020.

14. Heymann DL, Shindo N (February 2020). "COVID-19: what is next for public health?". Lancet. 395 (10224): 542–545.

15. Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020;395:497–506.

16. Li Q, Guan X,Wu P, et al. Early transmission dynamics in Wuhan,China, of novel coronavirus-infected pneumonia. N Engl J Med.2020.

17. Goldsmith CS, Tatti KM, Ksiazek TG, Rollin PE, Comer JA, Lee WW, et al. (February 2004). "Ultrastructural characterization of SARS coronavirus". Emerging Infectious Diseases. 10 (2): 320–26. doi:10.3201/eid1002.030913. PMC 3322934. PMID 15030705. Virions acquired an envelope by budding into the cisternae and formed mostly spherical, sometimes pleomorphic, particles that averaged 78 nm in diameter

18. Review Coronaviruses post-SARS: update on replication and pathogenesis.

19. Review Biochemical aspects of coronavirus replication and virus-host interaction.

20. Neuman BW, Adair BD, Yoshioka C, Quispe JD, Orca G, Kuhn P, et al. (August 2006). "Supramolecular architecture of severe acute respiratory syndrome coronavirus revealed by electron cryomicroscopy". Journal of Virology. 80 (16): 7918–28. doi:10.1128/JVI.00645-06. PMC 1563832. PMID 16873249. Particle diameters ranged from 50 to 150 nm, excluding the spikes, with mean particle diameters of 82 to 94 nm

21. Fehr AR, Perlman S (2015). "Coronaviruses: an overview of their replication and pathogenesis". In Maier HJ, Bickerton E, Britton P (eds.). Coronaviruses. Methods in Molecular Biology. 1282. Springer. pp. 1–23.

22. Lai MM, Cavanagh D (1997). "The molecular biology of coronaviruses". Advances in Virus research. 48: 1–100.

23. Cavanagh D, Mawditt K, Sharma M, Drury SE, Ainsworth HL, Britton P, Gough RE (August 2001). Schmidt A, Weber O, Wolff MH (eds.). "Detection of a coronavirus from turkey poults in Europe genetically related to infectious bronchitis virus of chickens". Avian Pathology. Birkhäuser Advances in Infectious Diseases BAID. Birkhäuser. 30 (4): 355–68.

24. Neuman, Benjamin W.; Kiss, Gabriella; Kunding, Andreas H.; Bhella, David; Baksh, M. Fazil; Connelly, Stephen; Droese, Ben; Klaus, Joseph P.; Makino, Shinji; Sawicki, Stanley G.; Siddell, Stuart G. (April 2011). "A structural analysis of M protein in coronavirus assembly and morphology". Journal of Structural Biology. 174 (1): 11–22.

25. Fehr AR, Perlman S (2015). "Coronaviruses: an overview of their replication and pathogenesis". In Maier HJ, Bickerton E, Britton P (eds.). Coronaviruses. Methods in Molecular Biology. 1282. Springer. pp. 1–23.

26. https://www.newscientist.com/article/2236544-coronavirus-are-there-two-strains-and-is-one-more-deadly/#ixzz6NAIX15ri.

27. Scientists demonstrate how COVID-19 infects human cells, https://www.drugtargetreview.com/news/56895/scientists-demonstrate-how-covid-19-infects-human-cells/

28. Q&A on coronaviruses (COVID-19)". World Health Organization (WHO). 17 April 2020. Archived from the original on 14 May 2020. Retrieved 14 May 2020.

29. "WHO COVID-19 situation report 29" (PDF). World Health Organization (WHO). 19 February 2020.

30. Arons MM, Hatfield KM, Reddy SC, Kimball A, James A, Jacobs JR, et al. (April 2020). "Presymptomatic SARS-CoV-2 Infections and Transmission in a Skilled Nursing Facility". The New England Journal of Medicine: NEJMoa2008457

31. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, et al. (February 2020). "Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study". Lancet. 395 (10223): 507–513.

32. "Symptoms of Coronavirus". U.S. Centers for Disease Control and Prevention (CDC). 20 March 2020. Archived from the original on 30 January 2020.

33. Hessen MT (27 January 2020). "Novel Coronavirus Information Center: Expert guidance and commentary". Elsevier Connect. Archived from the original on 30 January 2020. Retrieved 31 January 2020.

34. Report of the WHO-China Joint Mission on Coronavirus Disease 2019 (COVID-19) (PDF) (Report). World Health Organization (WHO). 16–24 February 2020. Archived (PDF) from the original on 29 February 2020. Retrieved 21 March 2020.

35. "Coronavirus Disease 2019 (COVID-19)—Symptoms". U.S. Centers for Disease Control and Prevention (CDC). 20 March 2020. Retrieved 21 March 2020.

36. "Coronavirus Disease 2019 (COVID-19)". U.S. Centers for Disease Control and Prevention (CDC). 11 February 2020. Retrieved 19 April 2020.

37. . "Q&A on coronaviruses (COVID-19)". World Health Organization (WHO). 17 April 2020. Archived from the original on 14 May 2020. Retrieved 14 May 2020.

38. "Q & A on COVID-19". European Centre for Disease Prevention and Control. Retrieved 30 April 2020.

39. How COVID-19 Spreads". Centers for Disease Control and Prevention (CDC). 2 April 2020. Archived from the original on 3 April 2020. Retrieved 3 April 2020.

40. To KK, Tsang OT, Chik-Yan Yip C, Chan KH, Wu TC, Chan JM, et al. (February 2020). "Consistent detection of 2019 novel coronavirus in saliva". Clinical Infectious Diseases. Oxford University Press.

41. COVID-19 and Our Communities -ACON – We are a New South Wales based health promotion organisation specialising in HIV prevention, HIV support and lesbian, gay, bisexual, transgender and intersex.

42. "Sex and Coronavirus Disease 2019 (COVID-19)" (PDF). nyc.gov. 27 March 2020. Retrieved 29 April 2020.

43. "Laboratory testing for 2019 novel coronavirus (2019-nCoV) in suspected human cases". World Health Organization (WHO). Archived from the original on 17 March 2020. Retrieved 13 March 2020.

44. "2019 Novel Coronavirus (2019-nCoV) Situation Summary". Centers for Disease Control and Prevention. 30 January 2020. Archived from the original on 26 January 2020. Retrieved 30 January 2020.

45. nterim Guidelines for Collecting, Handling, and Testing Clinical Specimens from Persons for Coronavirus Disease 2019 (COVID-19)". Centers for Disease Control and Prevention (CDC). 11 February 2020. Archived from the original on 4 March 2020. Retrieved 26 March 2020.

46. Real-Time RT-PCR Panel for Detection 2019-nCoV". Centers for Disease Control and Prevention. 29 January 2020. Archived from the original on 30 January 2020. Retrieved 1 February 2020.

47. Curetis Group Company Ares Genetics and BGI Group Collaborate to Offer Next-Generation Sequencing and PCR-based Coronavirus (2019-nCoV) Testing in Europe". GlobeNewswire News Room. 30 January 2020. Archived from the original on 31 January 2020. Retrieved 1 February 2020.

48. Brueck H (30 January 2020). "There's only one way to know if you have the coronavirus, and it involves machines full of spit and mucus". Business Insider. Archived from the original on 1 February 2020. Retrieved 1 February 2020.

49. Salehi S, Abedi A, Balakrishnan S, Gholamrezanezhad A (March 2020). "Coronavirus Disease 2019 (COVID-19): A Systematic Review of Imaging Findings in 919 Patients". AJR. American Journal of Roentgenology: 1–7.

50. Lee EY, Ng MY, Khong PL (April 2020). "COVID-19 pneumonia: what has CT taught us?". The Lancet. Infectious Diseases. 20 (4): 384–385. doi:10.1016/S1473-3099(20)30134-1. PMC 7128449. PMID 32105641. Archived from the original on 8 March 2020. Retrieved 13 March 2020.

51. Verdecchia, Paolo; Cavallini, Claudio; Spanevello, Antonio; Angeli, Fabio (12 April 2020). "The pivotal link between ACE2 deficiency and SARS-CoV-2 infection". European Journal of Internal Medicine.

52. Li YC, Bai WZ, Hashikawa T (February 2020). "The neuroinvasive potential of SARS-CoV2 may play a role in the respiratory failure of COVID-19 patients". Journal of Medical Virology

53. Zheng YY, Ma YT, Zhang JY, Xie X (May 2020). "COVID-19 and the cardiovascular system". Nature Reviews. Cardiology.

54. Klok FA, Kruip MJ, van der Meer NJ, Arbous MS, Gommers DA, Kant KM, et al. (April 2020). "Incidence of thrombotic complications in critically ill ICU patients with COVID-19". Thrombosis Research.

55. Wadman M (April 2020). "How does coronavirus kill? Clinicians trace a ferocious rampage through the body, from brain to toes". Science.

56. Barton LM, Duval EJ, Stroberg E, Ghosh S, Mukhopadhyay S (May 2020). "COVID-19 Autopsies, Oklahoma, USA". American Journal of Clinical Pathology. 153 (6): 725–733.

57. Jin YH, Cai L, Cheng ZS, et al. A rapid advice guideline for the diagnosis and treatment of 2019 novel coronavirus [2019-nCoV] infected pneumonia [standard version]. Mil Med Res. 2020;7:4.

58. Unite against COVID-19". Unite against COVID-19. Government of New Zealand. Retrieved 11 April 2020.

59. "Prevention & Treatment". U.S. Centers for Disease Control and Prevention (CDC). 15 February 2020. Archived from the original on 15 December 2019. Retrieved 21 January 2020. This article incorporates text from this source, which is in the public domain.

60. Advice for public". World Health Organization (WHO). Retrieved 8 February 2020.

61. Coronavirus public information campaign launched across the UK". Government of the United Kingdom. Retrieved 8 February 2020.

62. Kampf G, Todt D, Pfaender S, Steinmann E (March 2020). "Persistence of coronaviruses on inanimate surfaces and their inactivation with biocidal agents". The Journal of Hospital Infection. 104 (3): 246–251.

63. "Interim Recommendations for US Community Facilities with Suspected/Confirmed Coronavirus Disease 2019". U.S. Centers for Disease Control and Prevention (CDC). 11 February 2020. Retrieved 4 April 2020.

64. Coronavirus disease (COVID-19) advice for the public: When and how to use masks". World Health Organization (WHO). Archived from the original on 7 March 2020. Retrieved 9 March 2020.

65. . "Advice for public". World Health Organization (WHO). Retrieved 8 February 2020.

66. Singapore: The Model for COVID-19 Response?". MedPageToday.com. 5 March 2020. Retrieved 8 March 2020.

67. Nussbaumer-Streit B, Mayr V, Dobrescu AI, Chapman A, Persad E, Klerings I, et al. (April 2020). "Quarantine alone or in combination with other public health measures to control COVID-19: a rapid review". The Cochrane Database of Systematic Reviews. 4: CD013574.

68. What To Do if You Are Sick with COVID-19". U.S. Centers for Disease Control and Prevention (CDC). 11 February 2020. Retrieved 17 March 2020.

69. Stay at home: guidance for households with possible coronavirus (COVID-19) infection". Government of the United Kingdom. Retrieved 20 March 2020.

70. COVID-19 Travel Precautions". U.S. Centers for Disease Control and Prevention (CDC). 11 February 2020. Retrieved 6 March 2020.

71. Coronavirus disease 2019 (COVID-19) treatment guidelines. National Institutes of Health. https://covid19treatmentguidelines.nih.gov/introduction/. Accessed May 7, 2020.