Dr. Sujatha Pathirage
SARS-CoV-2 is an enveloped β-coronavirus with a genetic sequence very similar to SARS CoV1(80%) and bat corona virus RaTG13(93%). Viral envelop is coated by spike(S) glycoprotein, envelop and membrane(M) protein.
It primarily targets upper and lower respiratory tract. The angiotensin converting enzyme2(ACE 2) found in human cells, is the receptor protein that serves as the main entry point for corona viruses, including SARS CoV2, to enter the host cell.
The S1 subunit of the S protein contains the receptor binding domain and binds to host cell target receptor ACE 2.
ACE2 is widely expressed in the animal kingdom and its structure is highly conserved, i.e. relatively unchanged in the phylogenetic tree. Comparison of human ACE2 receptor with that of a finfish, for example, showed amino acid sequence identity of only 59 %. The very low genetic similarity of ACE 2 receptors, therefore, negates the possibility of the virus infecting aquatic food animals. In addition, fish does not have a lung with the exception of lung fish.
Most transmission occurs through close range contact, 15 minutes face to face and within 2 meter.
Spread of SARS CoV 2 is efficient in crowded places e.g. within household or gathering.
Household secondary attack rates (the proportion of susceptible individuals who become infected within a group of susceptible contacts with a primary case) ranges from 4% to 35%
Close proximity with the infected person, sharing food, and taking part in group activities are considered high risk activities. In addition, in an enclosed environment risk of infection is significantly increased.
Ability of SARS CoV 2 to be remained viable on smooth surfaces for many days and transmission of virus from these surfaces to mucosa of nose and mouth via unwashed contaminated hand will substantially contribute for transmission.
Food as a source of transmission
Food is not a major route of transmission of covid 2. However, there is a risk of food items getting contaminated from an infected food handler. Further, after transmission of disease to vendors coming from various parts of the country, during the stay at crowded places may initiate clusters of cases from different geographical areas of the country once they returned.
Currently there is no evidence to suggest SARS CoV 2 infect aquatic food animal. Aquatic food animals therefor do not play a role in transmitting SARS CoV2 to humans.
Although SARS CoV 2 can remain on the surface of fish or meat for prolong period once these get contaminated it does not get transmitted by eating properly cooked meat or fish. It will only act as a fomite. The virus would be inactivated through proper cooking and would be removed from food preparation surfaces by thorough cleaning and disinfection.
There for careful preparation and storing of fish without cross contaminating at home, washing all utensils with soap and water at the end of preparation and washing hands with soap and water after handling raw food will prevent transmission of SARS CoV2 with fish and meat.
It is very important to adhere to all health guidelines at food distribution markets both by the vendor and the consumer.
Whilst food is not considered to be a source or transmission route for COVID-19 it’s always important to follow the four key steps of food safety—cooking, cleaning, chilling and preventing cross contamination – to reduce the risks of all foodborne illness.