What Makes SARS-Cov-2 More Efficient at Spreading and More Lethal Than Other Viruses

Throughout history, mankind has had to live through many pandemics so Covid-19 is not the first. However, it is the only one in the past hundred years that has caused governments around the world to lock down their entire populations. What makes this virus particularly scary? Is it its Mortality rate, mode of transmission, or mutability? Read further to find out!

SARS-Cov-2

SARS-Cov-2

More than a year after the emergence of SARS-CoV-2 in Wuhan China, governments around the world are still confining their populations, and the virus has already lead to the death of 2.2 million people worldwide. The reason we can’t get rid of it is that the SARS-Cov-2 virus has a number of attributes that make it highly contagious and particularly dangerous.

A virus that spreads through the air

Ebola or AIDS viruses are transmitted through secretions or intercourse, which is much easier to prevent than respiratory transmission, as is the case with SARS-Cov-2, the latter is even worse than influenza, which is transmitted through contaminated droplets. A person infected with SARS-Cov-2 exposes more people to infection than influenza, probably because of the aerosolization of the virus.

A one-hour conversation in a room releases 460 times the viral load needed for transmission.

Droplets smaller than five microns can stay suspended in the air for several minutes or even hours. Not only do these small particles stay suspended longer, but they also penetrate deeper and more effectively into the lungs, increasing the risk of infection. An MIT study showed that speaking for an hour in a room releases 460 times the viral load needed for transmission between subjects. To make things worst surgical masks do not block particles smaller than three microns.

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A fast rate of mutation

In recent weeks, several variants have emerged that accelerate the dynamics of the epidemic and call into question the efficacy of vaccines. Although all viruses mutate frequently, SARS-Cov-2 is particularly more susceptible to these random mutations. According to a study by the Weizmann Institute in Israel, the virus is able to increase its affinity for ACE-2 receptors, which allows the virus to enter and penetrate cells, by more than 600 times. In other words, strains of the virus with such a mutation can be 600 times more infectious! By comparison, in the English and South African variants, which are already of great concern to us, transmissibility is increased only by four and twelve times, respectively.

Worse, preventive measures sometimes have the perverse effect of encouraging the spread of new variants. The use of an inadequately filtering mask can reduce the density of exhaled viruses below a level that no longer permits normal viral infection, but is still sufficient for contagious variants. These more infectious viruses are then gradually increased among the circulating viruses. This is also the case with vaccination: As standard viruses are slowed down, this might give a chance for the variants with higher affinity for the ACE-2 receptor.

Superspreaders that are hard to detect

The R0 value, which reflects the average number of people infected by a virus carrier, in no way reflects the reality of transmission. This is because 70% of patients do not transmit the virus to others, and 10% to 20% of patients contribute to 80% of infections. Coronavirus is therefore spread mainly by clusters in a sudden and unpredictable way.

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Theoretically, it would be sufficient to detect these superspreaders to avoid having to confine the whole population. Except that scientists have no clues on how to find them. According to a study published in MedRxiv, A person can suddenly become highly infectious for a day or two because the virus is often present in the respiratory tract intermittently for many weeks. This also explains why prevention through contact tracing is largely ineffective, as 70% of people do not infect anyone.

A lethality rate that is low

There are far more serious diseases than Covid-19, such as Ebola, where the virus kills up to 90% of infected people. Similarly, the mortality rate for SARS in 2003 was estimated to be 43% in people over 60 years old and 13% in people under 60 years old, compared to 0.23% to 1.15% for Covid-19. This makes it much easier to detect virus carriers. SARS 2003 was not contagious until after the onset of symptoms, so there was time to isolate patients before they could spread the virus to others. And they were even more detectable because they always had severe symptoms.

Read Also: Having Natural Immunity to the Original Coronavirus May Not Protect Against the South African and Brazilian Variants

With a more silent spread than SARS, Covid-19 eventually affected more people and caused more casualties.

With Covid-19, 59% of infections came from asymptomatic individuals, either during the incubation period or from patients who never develop symptoms. The lethality of a virus does not really indicate its dangerousness. With a more undetected and silent course than SARS, Covid-19 ended up affecting many more people and therefore causing many more victims.

Conversely, other highly communicable diseases, such as colds and influenza, have very low mortality rates, and no one ever thought of confining people for them, even during the worst epidemic periods.

A variety of symptoms

Although flu symptoms are well known (fever, chills, muscle aches, fatigue, headaches…), some symptoms of Covid-19 leave doctors perplexed. For example, gastric disturbances, skin manifestations, conjunctivitis, anosmia, ageusia, or even swelling of the tongue have been observed in some patients. The virus can also cause cardiovascular and cerebral complications. The particularly long duration of symptoms in some patients is also one of the features that make this disease atypical. A study published in the Annals of Internal Medicine stated that more than 30% of patients who caught SARS-Cov-2 have symptoms that last for at least six weeks after their infection.

Read Also: Sputnik V the Russian Anti COVID-19 Vaccine Is 91.6% Effective.

It is also impossible to predict which patients are more likely to develop a severe form of the disease(8-15% of cases). Although age, gender, obesity, and diabetes are known risk factors, some patients experience sudden and unexplained deterioration. This unpredictability in the course of the disease makes it very difficult to determine which populations should get vaccinated first and which patients should be treated more aggressively from the onset of the disease.

References

Clustering and super spreading potential of SARS-CoV-2 infections in Hong Kong

Wrong person, place, and time: viral load and contact network structure predict SARS-CoV-2 transmission and super-spreading events

SARS-CoV-2 RBD in vitro evolution follows contagious mutation spread, yet generates an able infection inhibitor

Report 34 – COVID-19 Infection Fatality Ratio Estimates from Seroprevalence

COVID-19 Symptoms: Longitudinal Evolution and Persistence in Outpatient Settings

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