Coronaviruses first broke out on 12th December 2019 in China, more accurately in Wuhan. At that time, COVID-19 was considered as epidemic with mysterious acute infection of the respiratory track of human beings. Studies have revealed that the possible emergence of the epidemic disease was from a sea food market located in Wuhan. Following 12th December 2019, the epidemic disease was classified as a novel coronavirus (nCoV/COVID-19). We did experience SARS-COV infection in Guangdong, China, back in 2002 and globally from the start of the year 2003. 2012 was the beginning of MERS-COV outbreak. Human coronavirus infections have again got the global attention following December 2019. It is to be noted that all of those three viruses mentioned earlier (COVID-19, SARS-CoV, MERS-CoV) are from the same family of viruses which is known as betacoronoviruses.
Back in 27th December 2019, three people were admitted to Wuhan hospital. They included a woman aged 49 years old, an old man aged 61 years and a man aged 32 years old. Those three patients were diagnosed with severe infection of their lungs by viruses. They had their alveoli filled with viruses and experience severe breathing difficulties. Authorities carried out investigations and revealed that the woman aged 49 years old was a well-known retailer in the sea food market of Wuhan and many clients and visitors got into close contact with the lady at the market including the old man who was a regular visitor and client at the woman’s stall. After tests were carried out at the hospital on those 3 people mentioned earlier, it was revealed that nCoV was the most likely etiologic agent for all of them.
Reservoir of viruses
There are more than one studies which reported that bats are the natural reservoirs for the SARS-CoV and MERS-CoV viruses (CoVs). Through the technique of sequencing complete set of genes/genetic material, COVID-19 was analysed throughout the genes to Bat CoV – RATG13. The result from the analysis revealed 96.2% overall genome sequencing identity. This means that human COVID-19 (also known as SARS-CoV-2) and bat CoV are identical. Based on the result above, bats have been suspected as natural host of SARS-CoV-2 viruses’ origin or that the viruses are transmitted via bats to an unknown intermediate host.
Intermediate hosts may have got into contact with humans leading to infection in human beings.
Intermediate hosts
However, bats are not available as food on sale in the sea food and wet animal market of Wuhan. Studies further reported through phylogenetic analysis that there are many species processing similar residues of receptors or that they have been infected by SARS-CoV-2 through contact with bats making them intermediate hosts. Species include turtles, pangolin and other fried snacks animal being sold at the market of Wuhan.
COVID-19 (SARS-CoV-2) in China
From 12th December to 27th December 2019, there is a lapse time of approximately 2 weeks. Studies reported that symptoms of COVID-19 viruses start to appear from the 14th day of infection, that is, nearly after 2 weeks in human beings. Human to human transmission of COVID-19 occurs when incubation carriers get into close contact with family members, friends and relatives. It is very likely that the woman retailer of Wuhan market and the 61- year-old man being incubation carriers of COVID-19 have been in close contact with people across different regions. Hence, infecting people from same and other regions as well.
Studies further revealed that there were many people who travelled to Wuhan and 31.3% of this population were found to be infected with nCoV upon testing. Furthermore, 72.3% of the population who are not residents of Wuhan and yet were infected with the virus are those who were in contact with people living in Wuhan.
As per the National health Commission of China released on 14th February 2020, 3.8% of Covid-19 patients are healthcare workers who got transmitted with the Covid-19 virus. They were victims of human to human transmission between themselves (healthcare workers). The emergence of COVID-19 is therefore suspected to come from the seafood and wet animal market of Wuhan-China. Direct contact with infected bats and intermediate carrier hosts, such as pangolin, through consumption is suspected to be the first main path of COVID-19 virus transmission. However, the sources and routes of transmission still remain partly elusive till to date.
Spread of the covid-19 outside Wuhan
Person-to-person spread was subsequently reported outside Hubei and in countries outside China, including in the United States. Some international destinations now have ongoing community spread with the virus that causes COVID-19, as do some parts of the United States. Community spread means some people have been infected and it is not known how or where they became exposed.
Worsening of Coronavirus situation and pandemic result
Air Travel and Globalisation
The current potential for global dissemination of COVID-19 was first through the occurrence of the Chinese New Year 2021 celebrations. A growing number of people from Wuhan and China travelled to different countries around the world. Unknowingly, they were already infected with COVID-19 viruses. They transmitted the virus to inhabitants of different countries though close and direct contact made. COVID-19 viruses have the ability to mutate at a rapid rate. This high rate of mutation makes the virus to easily adapt to varied hosts. This is why after the spillover event of the Lunar New Year celebrations; we have witnessed rapid human-to-human spread of COVID-19 viruses. We have also recorded confirmed cases in 29 countries approximately as at date making COVID-19 to rapidly evolve into a global pandemic. COVID-19 has produced large scale public health responses around the world. As at date, 06 April 2020, 1,291,313 cases of COVID-19 have been recorded officially. Furthermore, 70,659 people have died globally due to COVID-19. Underneath is a graphical representation from 22nd January up to date (after 27th March 2020) showing the total number of COVID-19 cases and total deaths around the world.
We can conclude that three parameters have been used to assess the magnitude of COVID-19 for being characterized as globally pandemic. Those parameters are:
Transmission rate, that is, the number of people already infected and those newly infected
Case fatality Rate, that is, the percentage/number of cases that ended with deaths
Possibility for asymptomatic transmission
Canada as example
There are many Government who did not implement airport lockdown at an early stage of COVID-19 outbreak. As a result, they could not contain the spreading and impact of COVID- 19 into their country. For instance, Canada did not stop flights from landing into its airport at the early stage of the outbreak. As reported by “THE GUARDIAN” on 18th March 2020, Air Canada did not even informed customers and their staffs enough about exposure to passengers who were already infected with the disease. Infected passengers have infected flight attendants who were tested positive for coronavirus. Air Canada unknowingly carried infected passengers at least on one occasion.
Flight attendants lacked adequate protective gloves, respiratory masks, face shields and disinfectant materials while carrying their jobs. They came into close contact with many passengers. Employee of Air Canada who became first confirmed cases of COVID-19 in Canada. The employee was initially infected in Germany. Later, 3 more employees in Calgary were tested positive.
After reported cases, the Canadian Government has laid off flights landing regarding non- citizens and stopped travelers from boarding inbound flights. Only some days after 18th March 2020 that the Government has called that anyone landing by flights in Canada have to self-isolate for days. Hence, infected passengers go landed before the date the self-isolation was implemented got into close contact with friends, relatives and other people transmitting the COVID-19 viruses (SARS-CoV-2).
Mauritius as example
Mauritius is features among the approximately 29 countries infected by COVID-19. The airline travel is the origin for the virus transmission in Mauritius leading to the emergence of COVID-19 in Mauritius. On 18th March 2020, the SSR International Airport of Mauritius was locked down completely such that no airplanes could land on our island. As from 23rd March 2020, no airplane could leave Mauritius to travel abroad. Before 18th March 2020, airlines landed at the airport. There were infected passengers who started to develop symptoms of COVID- 19 after landing in Mauritius. A passenger coming from Belgium landed in Mauritius on 27th February 2020 and died on 17th March 2020. It was not known by authorities nor his family members that he died due to COVID-19 infection. Medical tests carried out from 17th March to 21st March 2020 then revealed that COVID-19 viruses were the cause of the disease. This person travelled to different areas meeting friends and relatives. The viruses were transmitted to all those people through human-to-human close interaction.
On 13th March 2020, a Mauritian returning from U.K landed in Mauritius. He was aware of being incubation carrier of COVID-19; but consumed paracetamol on the flight so that he is not tested positive with COVID-19 upon landing at the SSR Airport. He was not quarantined. He travelled to different regions of the island and even went to a funeral. Human-to-human interaction was repeated again leading to transmission of COVID-19 viruses. The latter did not even wear any respiratory mask nor protective gloves while moving around the around and meeting people as testified by his close relatives who have been quarantined. He was tested positive on 18th March 2020 and die some days later. All the people who had close contact with him were tested positive of COVID-19.
Officially as at date for Mauritius, a total of 68 people coming from abroad including 67 Mauritians and 1 French were already infected with COVID-19 when they landed in Mauritius.
Airline travel fly more people more quickly between more places than ever before. This is why, there is great danger of COVID-19 spread by air passengers incubating the disease. On January 30, 2020, the World Health Organization (WHO) declared the outbreak of COVID-19 as a “public health emergency of international concern” (PHEIC) and was classified on 11th march 2020 as Pandemic.
Cruise ships outbreak revelation as a global context
Studies reported that many passengers were infected with COVID-19 without actually being aware. They went on a cruise ships for vacation. It all started on the cruise ship “Diamond Princess” where 700 passengers got infected with COVID-19 (nCov) which shows how fast the virus spread. On 1st February 2020, Diamond Princess left Hong Kong-China for Japan. A passenger was tested positive when the ship reached Japan on 3rd February 2020. The ship was immediately quarantined. After one month, out of 3,711 passengers and crew members, 700 people were infected following the 1st infected passenger. After this case, 25 other cruise ships confirmed that they have cases of COVID-19 as well. Grand Princess cruise ship have passengers who did not show any symptoms immediately after reaching the quay in California-America. 78 passengers from the cruise ship got into direct contact with people in California spreading the disease. It was after some days that they were tested positive and quarantined. Hence, they contributed to the outbreaks of COVID-19 in America.
Train travelling
So far, a total of 12 people who have travelled by train in India have been tested positive. The reason was due to one infected person who merged among other passengers on the train leading to close human-to-human contact. 8 passengers travelling on “AP Sampark Kranti Express” from New Delhi were tested positive on 13th March 2020. Furthermore, 4 passengers travelling by train “Godan Express” from Mumbai to Jabalpur were tested positive of COVID-19 on 16th March 2020. Hence, Railways company in India has appealed the population to avoid using trains to travel and to postpone all their journeys for their own safety.
Ways of COVID-19 transmission
Analysis of transmission
Respiratory infections can be transmitted through the different sizes of droplets. Droplets can be classified in different sizes, namely:
5-10μm
< 5μm
Current studies have revealed that Covid-19 is transmitted through droplets of size 5-10μm and routes of contact. Through a deep analysis it was explained that in China where approximately 75,465 COVID-19 cases were recorded (as at date on which the analysis was conducted), airborne transmission was not the cause of the virus infection transmission.
Droplets transmission
COVID-19 is transmitted to a person through droplets transmissions when the latter is positioned physically less than 1 metre from the infected person and is in close contact with the latter. The distance being less than 1 metre, any respiratory symptoms such as coughing and sneezing will release infective droplets that will easily get into contact with mouse, nose, eyes and body parts of the healthy person. He is at risk of potential infective respiratory droplets coming from the infected person.
Transmission upon contact with surfaces
Furthermore, COVID-19 viruses can stay active up to 72 hours on hard or shiny surfaces, for example doors, handles. They can stay up to 24 hours on porous surfaces. Therefore, touching those surfaces without wearing protective gloves can easily allows transmission of COVID-19 viruses to parts of the body (hands). There are cases where people got infected while doing shopping as they came into contact with infected surfaces or by handling cash payments before Government called for a complete lockdown.
Airborne transmission
In the COVID-19 context, there are unique circumstances through which airborne transmission has a possibility of transmitting COVID-19 viruses. There is still not enough evidence as at date to prove it; except in handful media contexts when one person is involved support treatments generating aerosols.
References
Mizumoto, K., Kagaya, K., Zarebski, A. & Chowell, G. Euro Surveill. 25, 2000180 2020).
Russell, T. W. et al. Preprint at medRxiv available at https://doi.org/10.1101/2020.03.05.20031773 (2020)
News on www.nature.com
Modes of transmission of virus causing COVID-19: implications for IPC precaution recommendations available at www.who.int
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.who.int/ith/diseases/sars/en/&ved=2ahUKEwjCm7eSvc_oAhVMQBoKHZK7Ac8QFjAAegQIARAB&usg=AOvVaw0bFoEUPELafXU98baC4o2k&cshid=1586027710108
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.who.int/csr/don/24-february-2020-mers-saudi-arabia/en/&ved=2ahUKEwjH-MPkvc_oAhUmyYUKHT8zA0oQFjAAegQIBBAB&usg=AOvVaw2F7Wd29imzm12U5jgJUE24&cshid=1586027861150
https://www.google.com/url?sa=t&source=web&rct=j&url=https://theconversation.com/amp/air-travel-restrictions-wont-protect-us-from-the-coronavirus-131237&ved=2ahUKEwiUgvzW79DoAhUIyIUKHRRKAbIQFjAOegQIBxAB&usg=AOvVaw3oSBt8cYq0Fl6QI4vVAo45&cf=1
https://www.theguardian.com/world/2020/mar/18/air-canada-coronavirus-staff-risks
Novel coronavirus 2019 (COVID-19): Emergence and implications for emergency care available at https://onlinelibrary.wiley.com/
The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak – an update on the status available at https://mmrjournal.biomedcentral.com/
https://www.deccanherald.com
https://mmrjournal.biomedcentral.com/