INFECTION PREVENTION AND CONTROL


Deactivating or destroying the virus So, if you can’t kill it, how do you defeat it? The virus is deactivated or destroyed when the structure of it falls apart. In pieces, it can’t stick to a cell to infect it, and so is rendered useless at transmitting infection. This is where the most important advice of this pandemic (and any pandemic or epidemic for that matter) has come in to play – ‘Wash your hands and cover your sneezes’. Soap is an amazing molecule, with one end that loves water (hydrophilic), and one end that hates it (hydrophobic). This means that when soap on your hands mixes with water and virus particles, the hydrophobic end of the molecule sees the fatty lipid part of the virus and tries to embed itself there to get away from the water. This disrupts the structure of the virus, and pops it open, spilling all the contents out, where they are surrounded by soap molecules and washed harmlessly away down the sink. Soap also helps stop the virus sticking to your skin, and removes any dirt that can protect the virus on your hands.


Alcohol hand rubs (over 60% alcohol) likely work in a similar way, disrupting the fatty lipid coat of the virus, causing it to fall apart. Other disinfectants also have similar actions, disrupting the virus. Any detergent or soap will have this effect; it does not have to be antibacterial or medicated soap, or ‘hospital grade only’ disinfectant.


Strong UV light


Strong ultraviolet light, another disinfectant, works by interfering with the structure of the RNA strand, so that if it does get into a cell, the RNA is scrambled, and can’t produce the right parts to assemble more viruses.


Once the structure and how to destroy it are known, it becomes easier to understand how to combat it – and also to determine if the ‘fancy’ new disinfectant/ filter/gadget that someone is trying to sell you is actually likely to work.


Where did the virus originate? While the question of where the coronavirus originated is one likely to be debated for decades to come, the most common explanation so far is that the virus crossed to humans from bats, and possibly via another animal such as a Pangolin or snake, in China. This is known as a zoonotic disease, ‘zoo’ meaning ‘from animals’. This has happened multiple times in the past with viruses, as humans encroach on animal habitats more and more, and come into closer contact with them. MERS was thought to have a source in camels, and Influenza has had sources in pigs and chickens. HIV is thought to have come from a primate. An increase in diseases passing from animals to humans has been predicted to be a by-product of global warming. With this history, and with decreasing habitat for animals, this will not


24 Health Estate Journal May 2021 Protein spikes for infecting host


Lipid membrane


Genetic material


Fig 2: The coronavirus is named after the protein spikes embedded in its surface.


be the last time that we encounter a virus that jumps from an animal host to a human host.


The first cases of the disease were notified in China in the Wuhan city of the Hubei region, late in 2019. From here it has spread worldwide, and very few countries are unaffected. Thanks to advances in modern molecular biology, the virus itself was identified and characterised very quickly, which helped develop reliable tests for infection – a key tool in combating spread.


How do you catch it?


Again, this is a rapidly changing field – at the beginning of the outbreak, the virus was thought to be animal to human spread; then human to human transmission was observed. While droplet spread was the main focus of initial interventions against spread, there is emerging evidence that some type of aerosol spread may also be involved. The identification of how the virus is spread is sometimes hampered by different groups


of professionals understanding different things by the word ‘aerosol’, but as more research is carried out, hopefully a consensus will be reached, and a unified approach to prevention can be reached. Droplet spread is spread from small droplets of moisture, such as those released by coughing, sneezing, singing, and talking. These droplets do not go far from the human body, and fall onto hands, clothing, and surrounding surfaces. These can be transferred to the face from the hands if they come into contact with the droplets, or, if a person is in close proximity to an infective person, they can be inhaled. Aerosol spread means (to an Infection Control person) that the virus is released in very tiny droplets that can remain suspended in the air for a long period of time, and can be transported on air currents, such as through air- conditioning. Being airborne makes a virus very difficult to combat. Airborne diseases such as measles and tuberculosis are very infective, and the air in a room can remain infective for some hours after an infected person has left. Thankfully, so far, COVID- 19 does not appear to be quite as infective as measles and tuberculosis. With other respiratory diseases such as Influenza, plenty of fresh air entering a building decreases infection rates.


Micelle


Fig 3: With their mixture of hydrophobic and hydrophilic parts, soap molecules can interact with both virus fragments and water molecules.


The effect of the spike protein Once the virus has been breathed in, or has contacted the mucus membranes in the mouth, the nose, and possibly the eyes, of a person, the aforementioned spike protein sticks to the outside of the mucous membrane cell, and the virus inserts its contents into the cell. Then, if the person’s immune system doesn’t neutralise it, the virus gets on with ‘hijacking’ the individual’s cellular machinery to make more of itself. Virus particles are then released from the infected person in a cough or sneeze, or by talking, and go on to infect more people. Unfortunately, in the case of


Adapted from: Jonathan Corum and Ferris Jabr/The New York Times


Adapted from: Jonathan Corum and Ferris Jabr/The New York Times


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64