In 2017, in Maryland, the farmers noticed that the pigs on the farm were sick. Feverish, with inflamed eyes, and running snouts.
The farmers taking care of the pigs eventually fell sick.
About 40 farm attendants were diagnosed with “Swine flu.”
Sick Animals do not generally infect humans. But when the cross-species infection or viral host jumps occurs, It can lead to deadly epidemics.
So, how can pathogens from one species infect another species?
And, what makes these host jumps, dangerous?
Viruses are organic parasites that are capable of infecting all living forms.
The virus uses three stages to survive and reproduce. First, they find a host. Then infect the host cells to multiply and release new virus particles. Finally, the new viruses must transmit to another host to spread the infection.
Let us take the example of the Influenza Virus. The virus enters the new host through its nose and mouth and enters the respiratory tract. Coming inside is not difficult for the virus. What is difficult is to survive in this new body. For which the virus must infect successfully before the body’s immune system can find and kill it.
To protect themselves from the immune system, viruses have evolved.
Human flu viruses are covered in proteins that have adapted to bind with matching receptors on the cells of the human respiratory system.
Once inside the cell, the viruses find new adaptations to hijack the host cell machinery to replicate its own genetic material.
Now the virus needs to either suppress or evade the host immune system long enough to replicate sufficiently to infect other cells.
At this stage, the flu can be passed on from one person to the other
This simple sneeze brings the virus in contact with other plants, and pets as well. So viruses constantly encounter new species, and make an attempt to infect them.
Most of the time, the virus fails in doing so.
Because the two hosts of different species are very dissimilar genetically.
We know that viruses replicate quickly by millions; this means there are chances that during this high-speed replication, random genetic changes can occur.
Most of these random changes either have no effect, or maybe deadly for the mutant virus.
But a small proportion may get strong enough and gain the ability to infect new species.
The probability of getting a host-jumping virus increases with time, and with the chance of two species being genetically more similar.
So for a virus infecting animals, it will only take a few lucky Mutations to be able to infect humans.
Because, even if a virus gains the ability to enter the human system, but fails to evade the immune response, it will not be successful in causing an infection.
And even If it evades the immune system, the chances that it will be capable of transmitting to other hosts is limited. For quick transmission, the virus must reach the saliva and cough from the bloodstream.
So only when the virus has mutated enough that it can enter human cells, Evade immune response, and transfer to others, that it becomes most dangerous.
And With each new host the virus gets more chance to multiply, which means more chance to have another successful random mutation.
Which can lead to viral epidemics/ pandemics
Scientists continuously try to study viruses, and predict the changes that can cause the next epidemic. But it is a challenging task. Once a new virus is out, the scientists are again challenged to create a new vaccine or treatment to stop the virus.
The farmers taking care of the pigs eventually fell sick.
About 40 farm attendants were diagnosed with “Swine flu.”
Sick Animals do not generally infect humans. But when the cross-species infection or viral host jumps occurs, It can lead to deadly epidemics.
So, how can pathogens from one species infect another species?
And, what makes these host jumps, dangerous?
Viruses are organic parasites that are capable of infecting all living forms.
The virus uses three stages to survive and reproduce. First, they find a host. Then infect the host cells to multiply and release new virus particles. Finally, the new viruses must transmit to another host to spread the infection.
Let us take the example of the Influenza Virus. The virus enters the new host through its nose and mouth and enters the respiratory tract. Coming inside is not difficult for the virus. What is difficult is to survive in this new body. For which the virus must infect successfully before the body’s immune system can find and kill it.
To protect themselves from the immune system, viruses have evolved.
Human flu viruses are covered in proteins that have adapted to bind with matching receptors on the cells of the human respiratory system.
Once inside the cell, the viruses find new adaptations to hijack the host cell machinery to replicate its own genetic material.
Now the virus needs to either suppress or evade the host immune system long enough to replicate sufficiently to infect other cells.
At this stage, the flu can be passed on from one person to the other
This simple sneeze brings the virus in contact with other plants, and pets as well. So viruses constantly encounter new species, and make an attempt to infect them.
Most of the time, the virus fails in doing so.
Because the two hosts of different species are very dissimilar genetically.
We know that viruses replicate quickly by millions; this means there are chances that during this high-speed replication, random genetic changes can occur.
Most of these random changes either have no effect, or maybe deadly for the mutant virus.
But a small proportion may get strong enough and gain the ability to infect new species.
The probability of getting a host-jumping virus increases with time, and with the chance of two species being genetically more similar.
So for a virus infecting animals, it will only take a few lucky Mutations to be able to infect humans.
Because, even if a virus gains the ability to enter the human system, but fails to evade the immune response, it will not be successful in causing an infection.
And even If it evades the immune system, the chances that it will be capable of transmitting to other hosts is limited. For quick transmission, the virus must reach the saliva and cough from the bloodstream.
So only when the virus has mutated enough that it can enter human cells, Evade immune response, and transfer to others, that it becomes most dangerous.
And With each new host the virus gets more chance to multiply, which means more chance to have another successful random mutation.
Which can lead to viral epidemics/ pandemics
Scientists continuously try to study viruses, and predict the changes that can cause the next epidemic. But it is a challenging task. Once a new virus is out, the scientists are again challenged to create a new vaccine or treatment to stop the virus.