In an attempt to prevent airborne spreading of infection, evidence-based measures propose to avoid overcrowding, likely to arise in public spaces and public transport. Banning of public assembly, closing down schools, while isolating the infected and confine the exposed [1], maybe useful at slowing down the spread of the virus.

In contrast, recommendations adopted by many authorities, to stay home with the exception of essential services, may contradict the principle of avoiding overcrowding. Across the majority of studies on respiratory diseases, the risk of acquiring the disease was associated with the house crowding index (number of co-residents per household, excluding newborn infants, divided by the total number of rooms, excluding the kitchen and bathrooms) [2].

According to the Italian National Institute of Statistics (ISTAT) [3], the national house crowding index for Italian households is well above 1 (the recommended value), suggesting that the Italian motto, announced by the Italian Prime Minister ‘’I stay home’’ should be changed, more appropriately, to “I stay alone”.

Enhancing natural building ventilation and promoting outdoor activities, while avoiding overcrowding, should be encouraged, as history proves these measures to be potentially effective in preventing airborne spreading of infections, as demonstrated by reports during the Spanish flu outbreak, where mortality rates were significantly lower in patients hospitalized in open-air facilities [4], compared to those housed in traditional hospitals.

Another advantage of spending time outdoors, in order to increase sunlight exposure, is related to vitamin D synthesis, which cannot occur indoors. Low levels of vitamin D may in actual fact increase the susceptibility to viral infection, such as influenza [5].

References

1. WHO (2014) Infection prevention and control of epidemic- and pandemic-prone acute respiratory infections in health care. Guideline I. World Health Organization 1–156. [View]
2. Chandrasekhar R, Sloan C, Mitchel E, Ndi D, Alden N, et al. (2017) Social determinants of influenza hospitalization in the United States. Influenza Other Respir Viruses 11: 479–488. [View]
3. Housing Crowding – Dati Istat www.dati.istat.it
4. Hobday RA, Cason JW (2009) The open-air treatment of pandemic influenza. Am J Public Health 2: S236–42. [View]
5. Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, et al. (2006) Epidemic influenza and vitamin D. Epidemiol Infect. 134: 1129–40. [View]