21. FLÜGGE MICRODROPS: Beckham’s crosses

Robert Koch and Carl Flügge sound like a fearsome pair of German forwards. This involuntary association of a German name with goalscorers may have its origin in Torpedo Müller, who back in the 1970s spread panic in the area of his rivals. Müller was world champion with Germany in 1974, and in 1972 he scored an incredible 85 goals, beating the record for goals scored in a calendar year. 40 years later, in 2012, a certain Lionel Messi reset the bar with 91 goals.

Koch and Flügge were two German stars, but they did not shine in the world of football. Both were born in Hannover, although too early to be able to play in Hannover 96, a football club that has won two German leagues and was founded in 1896. Robert Koch discovered the bacteria that cause tuberculosis and cholera, and for this finding, he received the Nobel Prize in Physiology or Medicine in 1902. Carl Flügge was a doctor friend of Koch, determined to consolidate Hygiene as a branch of Medicine. Flügge demonstrated that, when speaking, sneezing, coughing, or singing, microdroplets were produced that could carry viruses and bacteria. Both Koch and Flügge saved many lives that, unlike Müller’s goals, were never counted.

Flügge’s studies were very useful in the 19th century, and continue to be so today. Their findings, as with all scientific discoveries, were extended by others over time and with the help of new technologies. During the 20th century, aerosols, which are suspensions of tiny particles in a gaseous medium such as air, were studied. These studies help us to know that Flügge drops containing viruses can become part of aerosols, and remain suspended in the air for a while. A SARS-CoV-2 virus is about 100 nanometers in diameter, so it would fit 100 viruses in a one-micrometre aerosol particle (which is one-millionth of a metre), although the aerosol particles, which are largely diverse, are not solely composed of viruses but also contain many other microparticles.

In April 2020, an article was published in the journal Nature showing the results of measuring the presence of SARS-CoV-2 in the air (aerosols) of a Wuhan hospital 24. For this study they also used the famous PCR, but not the common PCR or the RT-PCR used in the tests, but the ddPCR (digital droplet PCR). With this technology, they estimated the amount of SARS-CoV-2 virus in submicron-sized particles (below one micrometre) and supermicron-sized particles (above 2.5 micrometres). In some areas of the hospital, up to 40 copies of the virus were detected per cubic millimetre of air. The researchers concluded that SARS-CoV-2 was not detectable in the air in common and ventilated areas, but that it had a high presence in aerosols from closed places such as patient toilets where, in addition, the dispersing effect of pulling the chain without lowering the toilet lid could result in putting more viruses into suspension, since the virus has also been detected in the stool of patients 25.

Finally, and before you panic, it must be said that the infective capacity of these viruses floating in the air is still unknown. Continuing with our simile of contagion equal to goals, being in open and ventilated spaces would be as if the opposite team attacked you with central passes from their defenders. These balls are very easy to clear, and it is difficult for them to score a goal by bringing the ball closer to your area in that way. However, if you lock yourself in a toilet in the Wuhan hospital used by a COVID-19 patient, the one who is crossing balls into the area you’re defending is David Beckham.