An amazing phenomenon almost went unnoticed this past flu season—there wasn’t one. Every year, the Centers for Disease Control (CDC) tracks reported cases of “influenza-like illnesses” on a weekly basis, and every winter there’s a very predictable, sharp increase. Except for this past winter, when reported cases of the flu were seemingly nonexistent.
Source: Centers for Disease Control (CDC)
Which raises a question. What if we could eliminate flu season every year? The CDC estimates that influenza viruses normally kill between 12,000 and 61,000 people a year in the U.S., and the World Health Organization (WHO) estimates the worldwide death toll from the flu at between 290,000 and 650,000 people a year. Even with the availability of partially effective vaccines, the flu has always seemed like an inevitable disease that everyone has to live (or die) with. Most of us don’t fear death from the flu, but missing a week of work or school is a part of winter that we have all become resigned to. And in total, airborne infectious disease is the third largest cause of death behind only heart-disease and cancer—and that is in a non-COVID year.
But this past flu season was different, for reasons catalogued in detail recently by the New York Times. Some experts say Covid infections simply got there first, effectively displacing influenza this year. But all agree that many anti-Covid public health measures—lockdowns, social distancing, hand-washing, and face masks—also played significant roles in making the flu disappear.
Dare we imagine a world free from deaths associated not only with Covid, but influenza as well? We certainly should, especially if we add disinfection from far-UVC light into the mix. Human-safe far-UVC light has been shown to be extremely effective in deactivating viruses, bacteria, and other pathogens. And recently, as its costs have come down, its availability for use as a general-purpose air and surface disinfectant has increased dramatically. In fact, far-UVC disinfection combined with other interventions someday may have the potential to deactivate so many airborne pathogens that Covid epidemics and the annual flu season become things of the past. Two recent avenues of research have provided some significant news supporting this dream.
Masks Block Virus-Laden Aerosols Behind “Super-Spreader” Events
First, public health authorities have only recently acknowledged that coronavirus germs suspended in aerosols in the air can linger in a poorly ventilated room for hours. Aerosols are now thought to have been a major cause of the “super-spreader” events that helped elevate isolated outbreaks into epidemics and finally into a global pandemic.
Initially, public health experts discounted the impact of aerosols, believing Covid-19 was spreading through physical contact with the virus in fomites on surfaces and in droplets expelled by people coughing or sneezing that quickly fall to the ground. The CDC and WHO therefore recommended social distancing, hand-washing, and deep surface cleaning to prevent infection, but said masks weren’t helpful or necessary.
Now, however, a growing body of research is demonstrating that aerosols can infect people further than six feet away, especially in poorly ventilated indoor spaces. Now that the CDC and WHO have acknowledged the role aerosols play in transmission, they are recommending more use of face masks indoors, along with much more attention to proper indoor ventilation. They also recommend more activities outdoors, where aerosols dissipate rapidly. Many experts now agree that, had face masks and better indoor ventilation been adopted sooner, many lives may have been saved. Moreover, these Covid-19 interventions can be equally effective in preventing the spread of flu and cold viruses.
Far-UVC Light Safely and Effectively Disinfects Viruses in Aerosols
But are face masks alone strong enough protection against virus-laden aerosols? Not quite, and here’s where the second avenue of research provides so much promise. It’s long been known that ultraviolet light in the UVC wavelength range effectively neutralizes viruses and bacteria along with a host of other pathogens in the air and on surfaces. And in the past several years, researchers have come to some surprising new conclusions about the efficacy and safety of various wavelengths of UVC light.
Invisible UVC light has been used in hospitals for a hundred years, starting with disinfection of the air in tuberculosis wards. But until recently, most UVC light sources emitted the disinfecting light at 254 nanometers, which can harm human skin and eyes with symptoms akin to sunburn and snow blindness. As with sunlight, long-term exposure can also lead to cancer. Therefore, UVC disinfection was limited to cleaning surfaces at night or other times when spaces were unoccupied, or to ceiling-mounted systems that disinfected some of the air circulating in the upper room without exposing people in the room below.
However, over the past several years, researchers at Columbia University, Kobe University, and elsewhere have demonstrated that a shorter wavelength of UVC light—“far-UVC” light at 230 nanometers or less—can be used more safely around humans. It deactivates pathogens equally well, but its shorter wavelength means it does not penetrate skin or eyes deeply enough to cause long-term damage.
The Holy Grail: Practical and Cost-Effective Far-UVC Light
As further studies confirm that far-UVC disinfection is human-safe, the possibilities for effective disinfection of the air in public and private spaces become nearly limitless. Constant disinfection of the air with human-safe far-UVC light should make it possible to significantly reduce the viral load anywhere people congregate. Always-on far-UVC light could make offices, airports and airplanes, trains and train stations, convention centers, buses, personal autos and ride-shares, theaters, and literally any other location where people gather far less likely to spread the contagion.
There have been some technical challenges delivering far-UVC light at wavelengths that are shorter and safer than the traditional standard 254-nanometer UVC light. Ushio and several other makers of UVC gas lamps have recently developed effective filters that block the more dangerous longer UVC rays while allowing the far-UVC light to disinfect the air and surfaces. However, these filtered far-UVC solutions are more costly, they can be hot to touch, and their use of caustic gases enclosed in a low-pressure lamp limits their ease of installation, use, and servicing.
To solve those problems, at NS Nanotech we developed the first solid-state far-UVC solution. Our semiconductor-based far-UVC lamp is smaller, runs cooler, contains no caustic gases or chemicals, doesn’t require a filter, and ultimately will follow a cost-reduction curve similar to other chip-based businesses. We’re confident that between our solid-state solution and the new far-UVC excimer lamps, the world will have access to a broad range of infrastructure solutions capable of delivering ubiquitous, human-safe UVC disinfection in public and private spaces worldwide.
For a deeper dive into how far-UVC disinfection infrastructure solutions can be integrated into our built environment, read my previous blog post, Rebuild for the Pandemic Era with Disinfecting UV Light.