Survival of the fittest is the core concept of the evolutionary theory — which emerged from the works of Jean-Baptist Lamarck and Charles Darwin, though they did not use the phrase — that explains diversity of life on Earth. It also says that species compete with one another for survival and as a result some species go extinct.
A new study conducted at the University of Glasgow in the United Kingdom has shown that the virus that causes common cold in humans competes successfully against the SARS-CoV-2, the coronavirus that has unleashed the Covid-19 pandemic. This common cold virus is rhinovirus, and it boots out the Covid-19 causing coronavirus.
It is estimated that rhinovirus could be responsible for up to 40 per cent of all common cold infections. The illnesses are usually short-lived. Viruses compete to survive in their hosts. Humans are an important host for a variety of viruses.
Some viruses are known for co-existing with their cousin viruses inside a human host. For example, adenoviruses can share their ‘home’ (a human cell) with other viruses. But influenza or common cold viruses are mostly lone warriors. They attack a human cell alone and prefer to stay home alone.
With this knowledge, scientists at the University of Glasgow used a replica of the human respiratory tract, which the SARS-CoV-2 uses to cause Covid-19 infection, for their experiment. They released SARS-CoV-2 and rhinovirus into this replica tract, leaving them free to infect the cells.
The scientists noted the timing of the release of the two viruses and found that if SARS-CoV-2 and rhinoviruses were released at the same time, the coronavirus was booted out by the common cold virus. This means that the infection of the respiratory tract was only of common cold.
When rhinovirus was released earlier giving it a 24-hour monopoly window, SARS-CoV-2 could not even get a start in the human cell replicas. Even when the advantage was reversed and SARS-CoV-2 was given a 24-hour solitary colonisation time, the rhinovirus came in later to boot the coronavirus out of the human cell replicas.
The conclusion was simple: Covid-causing SARS-CoV-2 has no chance when it has to face-off against rhinovirus.
“Our research shows that human rhinovirus triggers an innate immune response in human respiratory epithelial cells which blocks the replication of the Covid-19 virus, SARS-CoV-2,” explained Professor Pablo Murcia, from the university’s centre which conducted the research.
“This means that the immune response caused by mild, common cold virus infections, could provide some level of transient protection against SARS-CoV-2, potentially blocking transmission of SARS-CoV-2 and reducing the severity of Covid-19,” Professor Murcia was quoted as saying in the University of Glasgow press release.
Effectively, a rhinovirus infection can prevent a Covid-19 infection. But this is not the end of the story of Covid-19 pandemic.
A rhinovirus infection does not provide long-term protection against SARS-CoV-2. When the common cold illness is over, immune response generated by rhinovirus infection subsides within a few days. SARS-CoV-2 can then infect the person.
While this knowledge can be used by authorities in developing counter-Covid strategies, the scientists of the University of Glasgow said, “In the meantime, vaccination is our best method of protection against Covid-19.”
For record, this study also showed that rhinovirus had helped delay and curtail the 2009 swine flu pandemic in Europe.