COVID-19: What happens when a face shield wearer is exposed to an infected person's sneeze

The effectiveness of face guards in preventing droplets from spreading from an infected person's mouth is limited compared with masks. Wondering why? Read to know more.

How often do you see people wearing only face shields made of plastic and no face mask? While stepping out wearing just face shields on may seem like a more comfortable option than wearing those tight-fitting face masks like N95, but the truth is - these face shields may be completely ineffective without a face mask beneath.

A recent study has shown that face shields alone are not highly effective to prevent COVID-19 infection without masks. The findings also gave light to what happens to the airflow around these plastic screens when someone nearby sneezes.

The research, published in the journal Physics of Fluids, noted that the number of people using face shields as a substitute for face masks has been increasing in schools, universities, restaurants, and service businesses.

However, the scientists, including those from Fukuoka University in Japan, said sneezes produce a fluid phenomenon known as vortex rings that can capture microscopic particles and pass through the shield's barrier.

"A vortex ring is a donut-shaped vortex that is generated by an instantaneous ejection of fluid from a circular orifice. his resembles bubble rings made by dolphins," explained study co-author Fujio Akagi from Fukuoka University.

WHAT HAPPENS WHEN A FACE SHIELD WEARER IS EXPOSED TO AN INFECTED PERSON'S SNEEZE

In the study, the scientists assessed what happens when a face shield wearer is exposed to a sneeze from an infected person standing one metre in front of them.

"The vortex rings generated by the sneeze capture the microscopic droplets within the sneeze and transports them to the top and bottom edges of the face shield," Akagi said.

He added that the droplets travel to the face shield wearer quickly -- within 0.5 to one second after the start of the sneeze.

"If this arrival time is synchronised with inhalation, the shield wearer will inhale the droplets," he added.

HOW DOES THE VIRUS TRANSMITS

Based on the analysis, the scientists said droplets of sneezes are transported not only by the high-velocity airflow caused by sneezing but also by the vortex rings generated by sneezing.

They said the microscopic droplets transported by the vortex rings can get inside the shield through its top and bottom edges.

"It was also confirmed that some particles -- in this simulation, 4.4 per cent of the released droplets -- entered the inside of the face shield and reached the vicinity of the nose," the scientists wrote in the study.

WHY FACE SHIELD SANS MASKS ARE NOT EFFECTIVE

The researchers believe face shields alone are not highly effective to prevent COVID-19 infection.

However, by gaining a better understanding of face shield weaknesses, they hope to enhance protection by reducing the flow getting inside the shield.

"We are currently developing and demonstrating several improved shields," Akagi said.

"We want to contribute to keeping people safe from infection, and believe that one day in the near future, medical workers will be able to prevent infection using only a face shield and a regular mask or, ideally, with only a face shield," he added.

FACE SHIELD Vs. FACE MASKS

The effectiveness of face guards in preventing droplets from spreading from an infected person's mouth is limited compared with masks. Wondering why? Here are a few supporting facts.

#Almost 100 per cent of airborne droplets of less than five micrometres escaped through the gap between the face and the face shield.

#Face shields are understood to initially block droplets from a simulated cough, small droplets can easily move around the sides of the visor and eventually spread over a large area.

#Smaller particles of the infectious sneeze can remain airborne for a long time and flow around the face shield more easily to be inhaled.

SYMPTOMS OF SOMEONE INFECTED WITH COVID-19 VIRUS

Whether or not they have symptoms, infected people can be contagious and the COVID-19 virus can spread from them to other people. Some of the common signs include respiratory symptoms, fever, cough, shortness of breath, and breathing difficulties. In more severe cases, the infection can cause pneumonia, severe acute respiratory syndrome, kidney failure, and even death.

STAY SAFE AND WEAR A MASK WITH A FACE SHIELD

Looks like the pandemic is not going to end so soon. The virus is still infecting many around the world on a daily basis. Vaccination is here, but that does not mean the pandemic is over. Maintaining the basic pandemic rules are still in place and thus protecting your face and mouth with a mask and shield stands important.

Although the face shields provide good protection in an open place, it may fail to provide adequate protection in a crowded place or in a healthcare facility where the chances of getting exposed to the virus are greater. Whereas, a snugly fitting face mask such as N95 mask or a three-ply surgical mask if worn properly should provide for adequate protection against such exposures. One has to be always cautious, not to reposition or keep touching the mask to reduce the chances of exposure.

(With inputs from IANS)