Frequent hand washing, disinfecting surfaces and avoiding physical contact reduce the risk of contracting the corona like masks and gloves

This is according to a study by researchers from the Biological Institute in Ness Ziona, who built a mathematical model that reproduces the ways of infection of the virus, another finding: droplets suspended in the air are a negligible factor in infection

Frequent hand washing, disinfecting surfaces and avoiding physical contact reduce the risk of contracting the corona, as do masks and gloves. This is according to a study by researchers from the Institute for Biological Research in Nes Ziona. The researchers, Dr. Yehuda Arab, Dr. Ziv Kluizner and Dr. Eyal Patel from the Department of Applied Mathematics, at the Institute developed a mathematical model that reproduces the ways of infection of the virus.

One of the significant differences between the Sars epidemic and Covid-19 is the pre-symptomatic infection. While in SARS isolating people who showed symptoms led to the containment of the epidemic, in Covid-19 there is a significant rate of infection that occurs by people who appear perfectly healthy.

It is not clear how the presymptomatic infection occurs. In general, there may be several routes to infection: airborne virus particles, contact (direct with an infectious person or indirect through high-touch surfaces, called fomites in the literature) or large droplets that contaminate surfaces or another person. The discovery of the mechanism that allows pre-symptomatic people to transmit the SARS-CoV-2 virus has a significant impact on the possibility of controlling the COVID-19 epidemic. For this, proofs based on a quantitative mechanical mathematical model are required. The model follows the dynamics of infection between people inside a closed space.

The mathematical model The model describes typical behavior of healthy people working in a closed space (which simulates a room in an office or at home) when one of the people is pre-symptomatic, meaning infected with the virus, but does not show symptoms and the other is healthy. The study focused on closed spaces since many studies in the literature have identified that closed spaces are the environment where the majority of Covid-19 infections have occurred. The model takes into account measurement data from the scientific literature on the rate of contact that a person touches his face and on surfaces, the number of times a healthy person coughs and sneezes, data on the concentration of the virus in the respiratory system, the amount of virus particles emitted when a person coughs or sneezes and the decay of virus activity in the air and on surfaces.

The validation of the model was carried out against key parameters of the epidemic, which were measured around the world and reported in the research literature in recent months. - The secondary infection rate in households (that is, the average percentage of those infected in a household who were infected by a pre-symptomatic household member) also described a serial interval distribution - this distribution describes the time that passed between the infection of pairs of people - between the time when the infectious person became infected and the time when The man who was infected by him was infected. The data reported from around the world show a 15-10% chance of a healthy person being infected by an asymptomatic patient nearby at rates between 10-15% when all possible ways of infection are taken into account.

Once the model simulations successfully reproduced the aforementioned parameters, the model could be used to analyze the contribution of each of the possible modes of infection. It was found that the main infection is through direct contact between people and secondarily through contact with multi-touch surfaces. An important and interesting finding is that, contrary to the claims made in other studies, the danger of infection through the air is negligible.

The contribution of various protection measures was also examined. In particular, it was found that a combination of hand washing, cleaning high-touch surfaces and social distancing reduces the risk of infection in a similar way to wearing masks and gloves. This finding is very important regarding the recommended behavior in workplaces and schools. This can be used as a guideline that allows reducing the risk of infection when the economy returns to activity.

There are three possible forms of infection - the first is contact infection, which means large droplet infection that occurs when someone sneezes or coughs on another person and directly hits their face. A second way is through contact with contaminated surfaces, when the virus first reaches the hand and then when the hand is brought to the mouth, it moves to the respiratory tract, and the third way is through the air, droplets suspended in the air from a sneeze or cough of a patient who passed by the place earlier and are breathed in by another person.

The surprising result of running the model was that if you observe social distancing, and avoid shaking hands, observe hygiene when touching things and wash your hands once an hour, you reach the same protective effectiveness as wearing masks and gloves all day. Therefore, for example, sending children to school without masks can be sufficient if the school disinfects the surfaces all the time, and the children wash their hands frequently. It turns out that taking only one of the measures is not enough due to the extensive contact of the hands in the face, even unintentionally.

As usual in the days of the Corona, the research was first published on the archive website and at the same time sent to journals for peer review.

for the scientific article

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