The value of transfer of a coronavirus through the small air microdrops (which are also often called by aerosols) is intensively discussed in the context of COVID-19 SARS-CoV-2-pandemic (a heavy acute respiratory syndrome of a coronavirus-2 or a koronavirusny disease of 2019). It is considered that it is one of three standard ways of transfer of a virus. Two other ways are a way of transfer through the large drops which are allocated from respiratory tracts (for being near a source) and direct contact with the infected surfaces.
Now in several researches conducted in hospitals sampling of air for detection of SARS-COV-2 was made. In four of these researches detection in air of several positive samples of a genome (RNA) SARS-CoV-2 with use of the test of the polymerase chain reaction (PCR) was described, very small amount of positive samples was found in two, and only in one positive tests were not revealed. It shows potential risk of an airborne SARS-CoV-2 broadcast. Besides, in three researches it was specified about existence of quantitative data on virus RNA.
The greatest virus doses were found in samplers which were carried by the selected group in the presence of the patient receiving oxygen through a nasal cannula that indicates that this element of treatment can promote spread of a coronavirus by air.
Though now direct proofs of spread of a coronavirus are not enough in the airborne way, they will appear in process of continuation of a pandemic of COVID-19. On the contrary, a final way to airborne infection and contact transfer were always assumed through autoinfection of mucous membranes (eyes, a nose and a mouth). Strangely enough, today the direct proofs confirming this phenomenon no.
It should be noted that activators of some other infectious diseases (tuberculosis, measles, chicken pox) are recognized transferred in the airborne or contact and household way, or through aerosol systems. Measles and a virus causing chicken pox can be also effectively transmitted through direct contact during an acute phase of an infection. At close contact all ways of transfer can be potentially dangerous. For other respiratory viruses, including SARS-CoV, MERS-CoV (A Middle Eastern respiratory syndrome), a respiratory and syncytial virus (a common cause of a bronchiolitis at children) and flu, is possible transfer as at close and remote airborne contact, but it is difficult to define prevalence of remote transfer of a virus at various scenarios of influence quantitatively, and such way of transfer is opportunistic. The recent mechanistic modeling research showed that transfer in air at a short distance dominates on influence during close contact. Other researches connected with transfer of microdrops and schemes of an air flow between people also confirm an essential role of this way of infection.
Therefore, in the light of these proofs for other respiratory viruses, it is considered now that SARS-CoV-2 does not differ, at least, on a way of transfer in an airborne way indoors. Nevertheless, despite it, the international organizations of health care, such as WHO (World Health Organization), still pay insufficient attention to protection against small, infected with a virus, the drops which are present at air. Other organizations which are engaged in planning of control systems of the environment, recognized potential danger of air indoors and recommended the appropriate measures of control of ventilation of rooms. Infectious control specialists also often are interested in a role of airborne transfer in comparison with other types ("contact" and "drop"). Numerous researches give convincing proofs of transfer of viruses in rooms, especially in crowded with people and with bad ventilation. Nevertheless it is difficult to compare and draw precisely quantitatively a conclusion what way of transfer is most dangerous in this situation. Infection can occur on all ways of transfer of a virus in different degree and depending on specific conditions of influence.
Effective infectious control demands protection against all potentially dangerous ways of infection. In the conditions of uncertainty it is possible to claim that the strengthened filtration of particles and the disinfection of air promoting the general reduction of risk of aerosol infection in rooms will become obvious advantages of the effective ventilation system, perhaps.