How can light kill viruses?

How to kill a virus? Laser light is the new alternative, which is less damaging to human tissue than other methods. Read more on how to kill a virus.  See more modern medicine pictures.
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To stave off infection, there are some things you probably know you should do: wash your hands, be careful when you sneeze, gets lots of sleep, don't rub your eyes (especially after touching your nose), eat lots of fruits and vegetables. After all, a cold virus can survive on someone's hand for a couple of hours or for several days on some materials.

Even those hand sanitizers that many people use don't kill everything. And once they're in the body, viruses are quite tough to kill -- antibiotics are powerless against them and vaccines for influenza and some other viruses must be changed every year to adapt to new strains. Fortunately our immune systems can fight off many viruses, but some, like Ebola or even influenza, can be deadly. It may then surprise you to learn that something viruses are exposed to all the time -- visible light -- can be used to kill them.


A study by Kong-Thon Tsen of Arizona State University along with researchers at Johns Hopkins University shows how strong blasts of visible light from a low-power laser can kill viruses. The laser technique appears to be more successful than other methods at killing viruses, while also posing less harm to healthy tissue.

In their study, the researchers blasted a virus with a quick pulse of purple laser light. The laser, which only shines for 100 femtoseconds (a femtosecond is one millionth of a billionth of a second), causes the virus's capsid (its outer shell) to vibrate and become damaged. Essentially, the virus becomes "deactivated" while the area around the virus remains unharmed. The treatment doesn't cause viruses to mutate either, which is a problem in other virus treatments and can lead to viral resistance.

While the treatment is still in testing, it presents an array of potential applications. Serious diseases like HIV/AIDS and hepatitis could be blasted with laser light. Scientists could cleanse blood samples of viruses and other pathogens, making them safer to handle. Scientists could also combine the laser therapy with current blood dialysis treatments. In that case, blood would be cycled out of a patient's body, lasers could eliminate any pathogens in the blood and the blood would be cycled back in.

Future tests will focus on possible side effects, though as of yet, none have been discovered.

Doctors are limited in the ways they can fight viruses, which is why studies like this one are so exciting. On the next page, we'll look at more ways in which scientists try to fight viruses or stop their spread altogether. Several of them use light, whether to kill viruses or as an activating agent.

Other Ways to Combat Viruses

Photographer: Lisa F. Young | Agency:
Photographer: Lisa F. Young | Agency:
Meant for surgical masks and hospital garments, LaamScience’s coating aimed to drastically reduce the spread of disease.

While many efforts to stop viruses have yet to pass beyond laboratory trials, UV irradiation has already found its way into many real world applications. UV irradiation works by bombarding viruses with ultraviolet light, the same light that causes humans to develop sunburns and skin cancer.

Like the laser technique, UV irradiation kills viruses by breaking down their cell walls. Some ventilation and water-purification systems make use of UV irradiation to eliminate airborne or waterborne pathogens. Researchers have successfully used UV irradiation to kill food-borne pathogens, like E. coli bacteria, without diminishing taste or food quality. But while UV irradiation can be effective, it can also cause viruses to mutate and has the potential to damage healthy cells (as anyone who's suffered a sunburn can attest).


Some researchers hope to use microwaves to destroy viruses, but the technique has so far proved ineffective. The water surrounding viruses absorbs the energy from microwaves. The virus doesn't receive enough microwave energy to be affected, much less destroyed.

In August 2004, a team of Venezuelan and American scientists announced the development of rhodium-based compounds that destroy tumors and "deactivate" viruses. This technique also depends on light, using a specific frequency to activate the compounds. Scientists see the treatment as a potential alternative to chemotherapy, because it doesn't harm healthy cells. It could also be used, like the purple laser discussed earlier, to sterilize blood samples.

Part of treating viruses is preventing patients from ever contracting them. To that end, a company called LaamScience (which went bankrupt in 2013) developed a nanotechnology-derived coating that kills viruses and bacteria and can be applied to various surfaces, such as a surgical mask. The coating becomes active when it comes into contact with light. Once active, the area around the mask becomes toxic to viruses and bacteria. A person wearing a coated mask can still breathe normally and safely. The coating never has to be replaced or reapplied. Tests show that the coating should work against almost all viruses and bacteria.

For more information about viruses and related topics, please check out the links on the next page.

Related HowStuffWorks Articles

More Great Links


  • "New Compounds Use Light to Kill Tumors and Viruses, Scientists Say." US Department of State. Aug. 25, 2004.
  • "UV Irradiation Dosage Table." American Air & Water.
  • Cook, John. "HaloSource of Bothell lands $15 million." Seattle P-I. July 27, 2007.
  • Dumé, Belle. "Visible light pulses knock out viruses in blood." NewScientistTech. July 27, 2007.
  • Harris, Jaida. "Suntans are bad for bacteria too! Exposure to UV irradiation kills off harmful bacteria in food." Innovations Report. Dec. 15, 2003.
  • Khazeni, Nayer. "Chasing the Elusive Cold." San Francisco Chronicle. July 29, 2007.
  • Maurer, Allan. "LaamScience hopes to market germ-killing masks next year." TechJournal South. July 20, 2007.
  • Smith, Rick. "High-Tech Bug Killer: LaamScience Uses Light-Activated Nanotechnology Coating To Combat Viruses." WRAL. Dec. 13, 2006.