We all know that the flu virus is spread by airborne droplets. This can be directly, when a sick person coughed or sneezed, and standing next to healthy people inhaled the virus-containing air through a spray or drops produced by sneezing and coughing, and containing vibrios (virus particles); or by direct contact with secretions of the patient. However, scientists still do not know how is the flu spread.
Researchers from the University of Maryland under the direction of Professor Donald Milton decided to find out whether influenza virus to spread not only when you cough or sneeze, but just through breathing a sick person. About their work, the scientists shared in the journal Proceedings of the National Academy of Sciences.
From December 2012 to March 2013 doctors and biologists conducted surveillance of 355 volunteers, students aged 19 to 22 years, who had symptoms of SARS. 142 of them found influenza, and the remaining (healthy) did not participate in the experiments. Each participant of the experiment were in the process of sampling from the nasopharynx. On the fourth day after symptoms appear in people took samples of the exhaled air. The person asked for 30 minutes to breathe into a special instrument that collects aerosols. For that half-hour inside the device was a large (diameter greater than 5 micrometers) and small (less than 5 micrometers, but greater than 50 nanometers) droplets of exhaled aerosol. In the end, the scientists collected a total of 218 samples from the nasopharynx and respiratory samples. The researchers then analyzed the samples and different fractions of the aerosol for the presence of viral RNA. In addition, to check for viable virus in the secretions of patients the authors were grown viral cultures on the model of dog kidney cells.
Turned out to be that the viral RNA contained in 97 percent of samples from the upper respiratory tract, in 76 percent of the “fine” fraction of the aerosol (fine droplets) and 40% of the samples in the “coarse” fraction. Viable virus was detected in 89 percent of samples from the nasopharynx and 39% of the samples with small droplets of the aerosol. In his article, the researchers note that the vibrios were detected in half of the samples of breath people who do not cough and did not sneeze during the experiment. From this we can conclude that the drop in the exhalation was formed not as a result of sneezing or coughing, and with another mechanism. The authors suggested that the tiny droplets are formed in the lungs during expansion and contraction of bronchioles and exhale, come out.