Filter could provide cheap way to contain viral disease outbreaks

Using lab cleaning tissues and a chemical used for gene therapy, scientists in France have identified a new cheap way of filtering viruses.

The new filter could help with containing diseases during outbreaks, as described in the Chemical Engineering Journal by scientists from the University of Rouen and the University of Lyon.

The filter’s success hinges on the gene therapy chemical polyethylenimine, or PEI. Positively-charged PEI molecules attached to fibers in the cleaning tissues can capture negatively-charged viruses. In fact, when H5N2 viruses (a strain of the bird flu) were sprayed toward the filter as a test, no viruses were found past the filter.

Asked if this filter will be tested against other viruses, such as the more dangerous and more infamous H1N1 swine flu and H5N1 bird flu viruses, Trong Nguyen, a professor at the University of Rouen, replied, “We didn’t use H1N1 or H5N1 because of the problem of experimental cost. The H5N2 was available at the time from another experiment. And it is a little bit less dangerous then H1N1.”

Although there are no immediate plans to continue this research with other viruses due to the cost, Nguyen noted that a filter that works against H5N2 should work against other influenza viruses too.

The researchers hope that these filters will improve surgical masks. The use of surgical masks during flu season is a fairly common sight, as mask-wearers seek to contain germs or get germ protection.

However, masks are sometimes worn in vain. “Surgical masks are generally not very good protecting devices if you’re considering to protect the wearer,” says Sergey Grinshpun, professor of environmental health at the University of Cincinnati. “Instead, they’re good at blocking [contagious] particles from an infected person.”

According to Grinshpun, viruses leave people’s mouths via tiny water droplets, which the mask’s pores can block. However, airborne viruses are small enough to penetrate surgical masks, which don’t contain anything like PEI that can use electric charge attraction to capture viruses.

Masks that protect against airborne viruses already exist, rated N95 in the U.S. and FFP2 in Europe. These masks look like slightly clunkier versions of surgical masks, and unlike surgical masks, respirators also need to be fitted to the individual and are harder to breathe through.

“It would be practical to use them [N95 masks], for certain, but it wouldn’t be practical for everyone to use them,” according to Marc Lipsitch, professor of epidemiology at Harvard University.

The first issue is that ordinary people tend to misuse N95 masks—and surgical masks too, for the matter. They do this by not fitting them properly, by taking them off when they aren’t supposed to, and by reusing the masks, which are supposed to be single-use. (The proper use of masks is especially important in hospitals, where the spread of diseases is a serious problem, as evidenced in Toronto during the SARS epidemic.)

The second is a matter of cost, which was one of the factors that led to the N95 mask shortage in U.S. hospitals in the 2009 H1N1 pandemic, according to Lipsitch.

As explained in the paper by Nguyen and his colleagues, respirators are about five times as expensive as surgical masks, hence their motivation to create a cheaper antiviral surgical mask using PEI as an alternative. The paper also notes that PEI cannot be used in the filters of N95/FFP2 masks due to an incompatibility in materials.

The method used for making the PEI filters sounds similar to laundry. Lab cleaning tissues were soaked in PEI, left to drip, gently washed with water, air-dried at room temperature, and finally sterilized with UV light. “It’s very simple,” says Nguyen. “There should be no problem scaling up the process.”

It’s currently unknown how well these masks will market in real life. According to Nguyen, the public health community in France expressed a lack of enthusiasm towards the masks during a market study due to an unwillingness to change their mask procedures. Therefore, the success of these masks at virus protection may depend on something that is beyond innovation and laboratory experiments: how well the wearers of the mask use them, and how well they’re supplied.

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