Several types of viruses present concerns for hospitals and healthcare facilities. Two innovations for infection and contamination control are varying the acidity of the air and the application of copper surfaces.
Acidity
A new study shows that aerosols in indoor air can vary in acidity. This acidity determines how long viruses remain infectious in the air — with profound implications for virus transmission and strategies to contain it.
Some studies suggest that the humidity and temperature of the air may play a role in virus persistence. A factor that has been underestimated so far is the exhaled aerosols’ chemical composition, in particular its acidity and its interactions with the indoor air.
Hitherto, no research had been conducted on the effect the acidification of aerosols post exhalation has on the viral load they carry. The ETH Zurich, EPFL and the University of Zurich combined assessment has demonstrated how the pH of aerosol particles changes in seconds and hours after exhalation under different environmental conditions. Further, the study assesses how this impacts the viruses contained in the particles.
The data indicates that the exhaled aerosols acidify very rapidly. How fast they do this depends on the concentration of acid molecules in the ambient air and the size of the aerosol particles. The researchers examined tiny droplets — a few micrometres across — of nasal mucus and of lung fluid synthesised specifically for the study.
The acidic environment can have a decisive impact on how quickly viruses trapped in exhaled mucus particles are inactivated. This may lead to proposals for adding small amounts of volatile acids such as nitric acid to filtered air and removing basic substances such as ammonia in an attempt to accelerate the aerosols’ acidification.
Application of copper
Many viruses are stable in the environment for a very long time. A study has now shown that temperature is a major factor in this process. For the surface disinfection of viruses, alcohol-based or aldehyde-based disinfectants are more effective than hydrogen peroxide-based disinfectants.
Scientists from the University of Southampton have demonstrated how copper and copper alloys is effective against certain viruses, including norovirus. Studying norovirus prevention is an important part of health strategy since it is responsible for more than 267 million cases of acute gastroenteritis every year. The virus, for which there is no specific treatment or vaccine, can be contracted from contaminated food or water, person-to-person contact, and contact with contaminated surfaces.
The study was designed to simulate fingertip-touch contamination of surfaces and the results showed that norovirus was rapidly destroyed on copper and its alloys, with those containing more than 60 per cent copper proving particularly effective. Copper alloys have previously been shown to be effective antimicrobial surfaces against a range of bacteria and fungi.
The rate of inactivation was initially very rapid and proportional to the copper content of the alloy tested. One of the targets of copper toxicity was the viral genome and a reduced number of the gene for a viral encoded protein, VPg (viral-protein-genome-linked), which is essential for infectivity, was observed following contact with copper and brass dry surfaces.
