Question

1. Can we relate reaction rate with infection rate in biological or biochemical perspective? Can we relate reaction rate and reaction order with reproductive rate of the virus? what is the reaction order of COVID-19 infection or SARS-COV-2 infection?

Please explain in simple words thank you,

Answer 1

Infectious diseases occur frequently within last twenty years. The 2003 SARS

(Severe Acute Respiratory Syndrome), 2009 influenza A (H1N1), 2013 ebola virus,

and current coronavirus infected pneumonia (Covid-19) are among the deadliest and have

posed a strong impact on human lives and activities. Mathematical modeling and analysis

of infectious disease transmissions have been performed for a century. Its importance in

understanding infectious disease transmissions and developing practical strategies for disease control and mitigation have been demonstrated. Challenges remain in difficult descriptions of human contact patterns and virus evolution, due to randomness of human interactions and

unpredictability of virus growth especially for a new type of virus. The problems encountered

in disease transmission area are similar to many-body problems encountered in chemistry

and physics fields, where many entities like electrons, atoms, molecules, or nano-sized even

micro-sized particles interact each other in a disordered manner.

The Eyring rate process theory and free volume concept 13 have been employed to solve many-body problems without involving complicated quantum mechanical calculations. The

Eyring's rate process theory, originated from quantum mechanics, argues that every physical or chemical phenomenon is a rate controlled process, such as chemical reactions, electron transfer, conductivity, viscous flows, diffusions, etc. Every process needs an activated energy to move from the initial state to the final state. Free volume theory, originated from molec ular systems, is a most successful mean field theory in dealing with many-body problems.

All different kinds of interactions among entities are factored into a single term, the free

volume available in a system. Since the free volume theory resolves how large freedom an

entity may have and the Eyring's rate process theory describes how fast the process is, these

two theories have been integrated together to describe many seemingly

related systems

or phenomena like glass liquids, colloids and polymers, granules 10 18, electrical and proton conductivity 820, superconductivity and Hall Effect with great success.

In this article, we will utilize the Eyring's rate process theory and free vol une concept to describe infectious disease transmission process.

tious disease transmission is

The infection considered as a sequential chemical reaction. We

will follow the popular SIR (susceptible. infectious and removed) and SEIR (susceptible, exposed, infectious, and removed) compartment categorization method proposed in the literature to develop our theory. The difference between these two models can be found in literature' SEIR model can give more information like latency period. Each category will be treated as a chemical reactant". Its concentration or fraction expressed in the number of individuals in each segment divided by the total population in consideration will be estimated for unveiling disease transmission mechanisms and predicting peak time and peak infected population.

The reproduction number, or “R naught” (R0), is a mathematical term that defines contagiousness. Specifically, it is the number of people that one sick host can infect. If the R0 is less than one the disease will disappear. If the R0 ≥ 1 then the disease will spread between people. The slightly higher R0 for SARS-CoV-2 may be because it has a longer prodromal period, increasing the period during which the infected host is contagious.

Coronaviruses are generally thought to be spread most often by respiratory droplets, not to be confused with airborne transmission . Droplets are larger and tend to fall to the ground close to the infected host and only infect others if the droplet is intercepted by a susceptible host prior to landing. Droplet transmission is typically limited to short distances, generally less than 2 m. However, the airborne route involves much smaller droplets that can float and move longer distances with air currents. Under certain humidity and temperature environments, airborne droplets can remain in flight for hours. Generally, pathogens that are transmissible via the airborne route have higher R0, because infected particles can remain in the air long after the infected individual has left the premises. This airborne route occurs, for example, in measles and chicken pox.

Once infected droplets have landed on surfaces, their survivability on those surfaces determines if contact transmission is possible. Based on our current understanding from other betacoronaviruses, including SARS and MERS, coronaviruses can survive, and remain infectious, from 2 h up to 9 days on inanimate surfaces such as metal, glass, or plastic, with increased survival in colder and dryer environments . For this reason, the Chinese government has been reported to be disinfecting and even destroying cash in an effort to contain the virus . Reassuringly, cleansing of surfaces with common biocidals such as ethanol and sodium hypochlorite is very effective at inactivation of the coronaviruses within 1 min of exposure .

The timing of maximum infectivity is currently being assessed. A small study of 17 patients showed that nasal viral load peaks within days of symptom onset, suggesting that transmission of disease is more likely to occur early in the course of infection .