Prelims Nuggets

What are recombinants?

Co-infection of multiple lineages of a virus can lead to the exchange of genetic material between them through the process of recombination. Recombination is a process where genetic material from two different lineages of the same virus combines to form a new genome, which can give rise to chimeric genomes, or recombinants.

Recombinants may have the potential to create new lineages of the virus that possess better functional capabilities than either of the parent lineages. This is because the process of recombination allows for the combination of different genetic elements that may provide the virus with new functional advantages.

While most recombinations may not give rise to viable viruses, some rare recombinations could result in the creation of a new lineage of the virus. These new lineages may have improved pathogenicity, transmissibility, or other functional capabilities that make them more dangerous to human or animal health.

Why recombination happens so rapidly?

Since the replication of virus happens freely in the host cytoplasm, the process is completely unregulated. While the errors in DNA virus genomes can be corrected by the error-correcting function of cells in which they replicate, there are no enzymes in cells to correct RNA errors.

Therefore, RNA viruses, having a higher mutation rate than DNA viruses, tend to create recombinants rapidly. 

Unfortunately, the potency of a mutation to increase infectivity in a region can only be known retrospectively. 

Are all recombinants dangerous?

Most changes have little to no impact on the virus’ properties. However, some changes may affect the virus’s properties, such as how easily it spreads, the associated disease severity, or the performance of vaccines, therapeutic medicines, diagnostic tools, or other public health and social measures.

Why is XBB.1.16 a cause for concern?

• Amid the ongoing increase in the number of seasonal influenza H3N2 cases, an uptick in COVID-19 cases is also being seen in India in the month of March, despite the low number of testing. 
• The fast-spreading XBB.1.16 lineage is believed to be responsible for the recent spike in COVID-19 cases in India.
• XBB.1.16 presently accounts for more than 30% of all the sequenced genomes in the month of March 2023, and its proportion has been seen to be increasing in the past few weeks. 

It is important to monitor for the emergence of recombinant viruses because they can have significant impacts on public health.

For example, the H1N1 influenza virus that caused the 2009 pandemic was a recombinant virus that combined genetic material from swine, avian, and human influenza viruses.

This new lineage of the virus was able to infect humans and rapidly spread around the world, resulting in significant morbidity and mortality.

Is XBB.1.16 more infectious?

Based on preliminary data, there is no evidence to suggest that infections with the XBB.1.16 lineage differ in clinical severity from those caused by other Omicron lineages although the higher growth advantage and immune escape could lead to a higher risk of reinfection with XBB.1.16 compared to other circulating Omicron lineages. Protecting the vulnerable through time-tested means could therefore significantly blunt the rise in infections.

Major Highlights:

• Scientists discovered the data which consisted of genetic sequences posted by Chinese researchers in GISAID (a virology database).
• A Chinese team had reportedly collected samples from the Huanan Seafood Wholesale Market, which showed that several samples from the market containing the virus also had human genetic material in them.
• The main theoretical dualism that the world has contended with since the COVID-19 pandemic is the question of its origin — lab leak or zoonoses.
  • There is now a large body of peer-reviewed scientific research consistent with the zoonotic origin of this pandemic.
  • However, there is no credible, peer-reviewed research pointing to a lab leak. 
• However, the critics of the animal transmission theory are demanding specifics and details on the zoonosis theory, while virologists say it would be impossible to get that level of data. 

Zoonotic diseases:

• Zoonosis is an infectious disease that is naturally transmissible from vertebrate animals to humans. 

Zoonotic pathogens may be bacterial, viral, parasitic, or unconventional agents and can spread to humans through direct contact or food, water or the environment.

E.g., Salmonellosis, West Nile virus, Anthrax, Rabies, Bird flu, Malaria etc.