In the light of our knowledge of ways of transfer and distribution of SARS-CoV-2, is of particular importance prevention of an airborne way of infection. In this article we will consider various ways of control over transfer of new type of a coronavirus.
For the maximum protection of the population against aerosol distribution of SARS-CoV-2 and microdrops infected with a virus, at the moment time there are several recommendations. They are focused on intra house rooms as exactly there is a transfer of a virus in most cases. Besides, the proposed measures are generally applicable also to public buildings. In houses and apartments, usual methods (for example, isolation of the infected people, opening of windows and doors and use of portable devices of purification of air when it is possible) indoors have to be applied to providing healthy air constantly. The existing ways of protection of ventilation can be easily improved at rather low costs for reduction of frequency of infections and, therefore, for rescue of lives. The options described below have to be always used in combination with other existing measures (for example, washing of hands and use of individual protection equipment), for reduction of transmission of infection in other ways as any of them cannot be completely excluded.
Important factor of control over a SARS-CoV-2 broadcast is optimization of ventilation systems that we will consider in separate article. In conditions when it is difficult to improve ventilation, there can be useful an addition of local devices of cleaning or disinfection of air, such as bactericidal ultraviolet radiation. It was in vitro proved that ultraviolet is effective against a number of microorganisms, including coronaviruses, a virus of a variolovaccine and mycobacterium. Several researches show that the inactivation decreases with increase in humidity both for bacterial, and for virus aerosols. Also it was shown that SARS CoV-1 can be inactivated by ultraviolet rays of a range of S (UF-S). For SARS CoV-2 there are no such data, but data on other coronaviruses show a high probability of their susceptibility to UF-S. The way of indirect UF-radiation is well applicable technology for use in the crowded, badly ventilated environments where there can be a transmission of infection in the aerosol way, but at the same time the possibility of optimization of ventilation is limited. The data showing the termination of transfer of flu in a hospital situation were provided in one research. Well designed radiation UF system installed in the top part of the room can effectively kill or inactivate the majority of the mycobacteria which are in an airborne suspension if the average intensity of UV-radiation is in range from 30 mkvt/cm2 up to 50 mkvt/cm2 provided that other recommendations are observed. Besides, lamps have to be established so that to provide as much as possible hypodispersion of bactericidal ultra-violet radiation in the top part of the room.
Portable household devices of purification of air can be useful in small rooms though it must be kept in mind that the model of such devices has to correspond to the size of space in which they are used. Range of capacity of air cleaners strongly varies depending on their model and the size of the room in which they are used. A useful indicator for determination of productivity is the intensity of forcing of clean air which is equivalent to a volume flow rate of the air without foreign debris produced by the air cleaner.
It is also necessary to minimize the number of people in rooms in the conditions of epidemic This measure concentration of air-borne virus particles and reduction of number of people which can catch at any time is obvious in the context of need of decrease. There is no concrete value for a number of people, being in the same space at the same time during a pandemic, and this measure has to be considered in combination with engineering ways of control, especially concerning parameters of ventilation of the room. Though the physical distance necessary for prevention of transfer through direct contact dictates requirements to the number of square meters on the person, the speed of air exchange and efficiency of ventilation are parameters which control concentration of virus microdrops in the air exhaled by persons and will be decisive factors when determining safe number of people.