Raina Pang
Nov 11, 2011

Breathe easy this flu season - new material captures the flu before it gets to you

Sniffly, sneezy, achy, feverish and overall icky is what is in store for the 5 to 20 percent of the US population that will suffer from the flu this year. Over 200,000 will require hospitalization. In the most serious cases the flu is deadly. Annually, an average of 23,600 deaths are attributed to the flu. Loss of workers and increased health care costs make the flu economically burdensome as well.


The costs associated with the flu, which is caused by the influenza virus, make it clear that effective prevention of the virus is essential. While vaccines play an important role in flu prevention, the fast mutation of influenza and lengthy process of vaccine development diminishes the effectiveness of this measure.


Because of the limitations to current approaches to preventing the spread of influenza, emphasis is placed on finding materials that can effectively capture the virus and prevent its spread. Researchers at the Chinese Academy of Agricultural Science have created sialyllactose (SL) incorporated chitosan based materials that are able to bind to the influenza virus. These materials may provide another approach for virus prevention and decontamination.


Influenza transmission occurs through the air by coughs and sneezes. It can also spread through nasal drippings and contaminated surfaces. Two large glycoproteins on the outside of the viral particle determine the host range of the influenza virus: hemagglutinin (HA) and neuraminidase (NA).


Since sunlight, disinfectants and detergents inactivate influenza, good health hygiene is emphasized as the first line of prevention during the flu season. The other major preventative measure is influenza vaccination. Vaccines work by presenting an inactivated or weakened virus that cannot replicate. This inactivated or weakened virus stimulates the body to produce antibodies specific to the virus presented. After two weeks the body produces enough antibodies to fight off the virus in case of exposure.


As flu vaccines cannot encompass every type of influenza strain currently causing infections, epidemiologists must predict which strains to incorporate in any given years influenza vaccine. Occasionally, scientists miss the mark or there can be strong antigenic shift, i.e. sudden gene reassortment resulting in new HA or HA and NA. Since vaccines effectively only stop infections of the specific strains incorporated and production of vaccines takes at least six months, these situations can result in a population with minimal protection to circulating influenza strains, which can quickly rise to pandemic status.            


Knowledge about how influenza binds to host cells provides a novel avenue to influenza prevention. It is known that HA on the surface of the influenza virus binds to host membranes via their sialyl sugar chain receptors such as SL.; thus HA binding can be a target for virus prevention. SL-incorporated citosan based materials, a water-soluble polymer and a functional fiber, bind the influenza virus in laboratory testing; thus inhibiting it from binding to other host cells.


While these results are quite promising the actual application of this knowledge is unclear. Although there is clear binding in a lab setting, these tests have not been conducted in the open-air environment that influenza normally spreads in. The intention is to use this material in facemasks and air filters, but does this material work any more efficiently then what is currently used? No definitive test has proven that facemasks inhibit viral infection, but studies do suggest that they can reduce viral transmission.


The main problem with facemasks in lowering viral transmission is a low adherence rate to their use; thus the limitation to face mask efficacy in viral transmission reduction may be their use rather than the material they are made of. Current high-powered air filters have already been shown to remove influenza virus downstream of their use. The main issue though is that generally people do not stand with an air filter between them. So the true effectiveness of air filters in viral prevention may also be limited to the range of air purification rather then the filtering material.            


Flu season gets everyone concerned. Whether it be a new strain or not, influenza infection can be quite painful and even deadly. While any step to reducing the spread of influenza is important, the true test of anything is in the real world. The chitasan-based material does seem quite effective in binding influenza virus is lab setting, but does this translate to real world settings? Only further testing will tell.