'Surveillance, testing key to identify silent COVID-19 infections'

Continuous surveillance and testing for the novel coronavirus are critical for identifying and preventing the transmission of 'silent infections' by people who do not show any symptoms but carry the virus that causes the deadly COVID-19 disease, according to a leading virologist.

According to Naga Suresh Veerapu, Assistant Professor at Shiv Nadar University in Uttar Pradesh, some virus infections can remain silent for many years until the damage to the organs is enough to manifest as disease signs and symptoms.

"Asymptomatic infections are also known as silent infections. Surveillance and testing is critical to identify silent infections and further prevent transmission," Veerapu told PTI.

Veerapu, who has been researching infectious diseases for more than a decades, noted that during aerial transmission of the novel coronavirus, the droplets produced when a COVID-19 infected individual sneezes or coughs are too large to be airborne for long distances.

"Due to the large size of the droplets, they settle down quickly on nose, mouth, eyes or may travel a three feet distance falling on nearby objects," the scientist explained.

On the other hand, he noted that particles of measles virus can travel up to a 100 feet distance, meaning one can still be exposed to the air-borne virus even if the individual is not in close contact with an infected person.

The virologist noted that certain host tissues and organs preferably support infection and proliferation of certain viruses a phenomenon called as tissue tropism.

"COVID-19 infects and proliferates in the epithelial cells of the lungs, hence it transmits via droplets," he said.

The scientist said viruses constantly explore new susceptible hosts for their continuous survival and to settle in new intermediate hosts, and at times they are even successful in "species jumping".

"Viruses can change their genome sequence by mutations and they may reflect the changes in viruses' antigenicity and disease severity," he said.

Veerapu, however, noted that many genetic mutations are bad for viruses, while some are beneficial for them.

He explained that in order to find the intermediate and reservoir host of a virus, continuous surveillance and testing is important to identify whether there are new reservoirs for emerging infections.

"Molecular diagnostics and immune surveillance help identify intermediate hosts," he added.