Infectiousness of SARS CoV 2

While the zoonotic origins of the SARS-CoV-2 virus has been confirmed through epidemiological linkage of initial cases to the exposure to Huanan seafood market in Wuhan, known to trade wild animals, as well as discovering that bats are reservoirs of the virus strain, the common hypothesis that the first non-human to human transmission of the virus occurred through consumption of bat meat is highly unlikely. This is so since at the time of first non-human to human transmission, bats species in Wuhan were hibernating, and investigations showed that no bat meat was present at the market (Lu et al, 2020). Moreover, the bats are known to be reservoirs of the virus not intermediate hosts; that is, bats are not part of the lifecycle of the virus else it would replicate and affect the bats, classifying them as intermediate hosts not reservoir. It is more likely that an, as of yet, unidentified, terrestrial intermediate host/s sold at Huanan market caused the first infection of humans. Nonetheless, it is important to also note the virus is an RNA-virus; which are notorious for very fast mutation rates. Therefore, it is still possible that a mutation event rendered the virus capable of replicating in humans after it had already been transmitted to the first human host.

Due to its zoonotic origins, it was initially feared that the mode of transmission of the virus was through consumption of some infected meat. However, despite closure of Huanan market, the disease continued to spread and it was quickly determined that the principal mode of propagation of the infection was through contact with infected individuals. Detailed studies of the viral infection showed that the virus targets human respiratory epithelial cells via interaction between viral S protein and angiotensin-converting enzyme 2 receptor (Xu et al ,2020), making it very infectious to humans. Transmission mechanism has been found to be predominantly through droplets and fomites in recent, close, prolonged exposure to infected individuals (WHO-China Joint Mission, 2020). There is no evidence that the virus is capable of airborne transmission (WHO-China Joint Mission, 2020).

The situation, so far as of 1st March 2020, is a cumulative total of 87,470 laboratory-confirmed cases of infected individuals, of which 66,907 occurred in Hubei province. Currently, there are 41,810 existing cases worldwide, of which 34,946 (83.58%) are contained in mainland China. In mainland China; 32,610 or 93.31% of those existing cases are restricted to Hubei province. This has been achieved through successful quarantine measures employed by Chinese authorities which have contained the spread mostly to Hubei province and aggressively quarantined and limited the spread of the viruses in other provinces. The result is that in all provinces excluding Hubei, the number of currently existing, confirmed cases is below 330. Outside of mainland China the virus has been exported to a total of 66 countries, with 87.21% of active cases outside of mainland China being concentrated in Korea (50.68%), Italy (15.34%), Iran (10.91%) and the Diamond Princess cruise ship (10.27%) (Dong et al, 2020).

Compared to other betacoronavirus outbreaks such as SARS-CoV in 2002 which infected 8000 people and MERS-CoV in 2012 which infected 1000 people it is very clear that SARS-CoV-2 is highly infectious and more difficult to contain despite intensive containment efforts. However, in China successful containment is very close to being achieved, as the most recent epidemiological curve (Figure 2) shows that the number of daily new cases in mainland China has decreased significantly. There is still the possibility that this may simply be the first incubation period or first wave of the epidemic, but should the number of new cases remain low for over two weeks (median incubation period of the virus is 10.5 days), it would mean that China has successfully contained the virus (WHO-China Joint Mission 2020; Shi et al, 2020). It should be commented that similar data is not yet