[Suggestion to school pharmacists to utilize absolute humidity parameter for maintaining air-conditioning].

One of the major roles of a school pharmacist is to maintain adequate air conditioning in the school to prevent the spread of infectious diseases. Influenza, the most important infectious disease at school, can be a cause of temporary closure of classes. We ordinarily examine relative humidity (RH), a popular parameter in the pharmaceutical field. However, RH is the ratio of vapor pressure to saturation vapor pressure at the indicated temperature and does not indicate the actual amount of water in the atmosphere. RH is temperature-dependent and varies easily with temperature. The use of absolute humidity (AH) is not common among school pharmacists because calculating AH from the measured temperature is not straightforward. In addition, commercially available humidity meters are usually designed for RH. We surveyed the relationship between climate data and influenza epidemics in Kobe from 2007 to 2012. We found that AH is more closely correlated with the number of patients than RH and that there is an AH threshold at which an influenza outbreak can occur in Kobe: 10 g/m(3). The 2009 epidemic pattern, when influenza A (H1N1) virus spread throughout the country, was irregular and AH did not correlate with the number of patients. Because AH can be easily measured using a computer without the need of any additional instruments, we suggest that school pharmacists utilize AH in combination with temperature as a better parameter for predicting the onset of influenza epidemics. When AH in Kobe decreases to 10 g/m(3), schools should be immediately cautioned.