Ultraviolet Light and Viruses

• 12 May 2020

Why in News

As nations begin relaxing restrictions, scientists are studying the use of ultraviolet germicidal irradiation (UVGI) to detect the virus in public places and disinfect contaminated public spaces to stop the transmission of the virus.

Key Points

• Ultraviolet Light:
  
  • UV light from the sun has shorter wavelengths than visible light so it is not visible to the naked eye.
  • UV radiation’s full spectrum is sourced from the sun and can be classified into UV-A, UV-B and UV-C rays according to their wavelength.
  • They differ in their biological activity and the extent to which they can penetrate the skin.
    
    • The shorter the wavelength, the more harmful the UV radiation.
    • However, shorter wavelength UV radiation is less able to penetrate the skin.
  • Research shows that UV light kills cells and increased exposure can cause cells to become carcinogenic (cancerous) and increases the risk of getting cancer.

Classification of UV Radiation

• UV-C:
  
  • Short-wavelength.
  • Most harmful but are completely absorbed by the Earth’s atmosphere and does not reach the Earth’s surface.
• UV-B:
  
  • Medium-wavelength.
  • Biologically active but cannot penetrate beyond the superficial skin layers.
  • Responsible for delayed tanning and burning.
  • Enhances skin ageing and significantly promotes the development of skin cancer.
  • Exposure to UV-B rays can cause DNA and cellular damage in living organisms.
  • Most solar UVB is filtered by the atmosphere.
• UV-A:
  
  • Relatively long-wavelength.
  • Accounts for approximately 95% of the UV radiation reaching the Earth's surface.
  • Penetrate into the deeper layers of the skin and is responsible for the immediate tanning.
  • Enhances the development of skin cancers.

• UVGI Working Method:
  
  • UVGI replicates UV wavelengths and uses its destructive properties to target pathogens.
  • It disinfects contaminated spaces, air and water and helps in preventing certain infectious diseases from spreading.
  • According to the US Centers for Disease Prevention and Control (CDC), UVGI is a promising method for disinfection.
    
    • In 2005, the CDC revised its guidelines for using UVGI with regards to the spread of tuberculosis (TB) in hospital settings.
    • The guidelines intended to eliminate the spread of infection to healthcare workers from patients or others with unsuspected or undiagnosed infection.
  • Scientists advise that fixtures containing UVGI lamps can be mounted on the walls or suspended from the ceilings.
    
    • Such fixtures will shine light on the upper interior surface of a room and trap pathogens.
    • Installing a fan in such spaces can further draw the air upward, which will increase the speed with which the UVGI can destroy pathogens.
  • UVGI lamps can also be installed in room corners, in air ducts of ventilation systems or portable or fixed air cleaners.
  • UVGI fixtures are and should be installed above people’s heads because their short wavelengths can irritate the skin and eyes.
• Effectiveness:
  
  • According to research papers, UVGI is most effective in preventing infections which are mainly spread through smaller droplets and not by direct contact or larger respiratory droplets.
  • The efficacy of UVGI depends on several factors, such as:
    
    • Sensitivity of microorganisms to UVGI.
    • Dose/ intensity of UVGI required to kill pathogens.
    • Humidity and weather conditions.
    • Air circulation in a room.
      
      • It should be such that the air from below the room, where the pathogen is generated reaches the upper-portions of the room, where the UVGI can trap and kill the pathogen.
  • However, using UVGI on a mass-scale in public spaces like schools, universities, restaurants and cinema halls is not a very cost-effective way for disease prevention.
• DRDO’s Latest UV Developments: The Defence Research and Development Organisation (DRDO) has recently developed automated contactless UV-C devices namely DRUVS (Defence Research Ultraviolet Sanitiser) and NOTESCLEAN.

Other Measures

• Apart from using modern technology to combat viruses, it has been suggested to bring behavioural changes like social distancing and wearing masks.
• Few countries have considered issuing immunity passports or risk-free certificates.
  
  • Such certificates are based on the idea that the natural immunity a person develops to any infection will protect them from contracting the disease again.
    
    • Once infected with a viral pathogen, the body’s innate immune response kicks in and slows the spread of the virus.
    • This response is followed by an adaptive response, wherein the body makes antibodies, which bind to the virus and help eliminate it.
    • If this response is strong enough, it might prevent reinfection from the same pathogen.
  • However, the World Health Organisation (WHO) has warned against using immunity passports because there is, yet, no proof of immunity from the reinfection of Covid-19.
    
    • Even if there is an immunity, its duration is not known.

Source: IE