The main reason that influenza viruses can cause major outbreaks is because their RNA replicase is error-prone.
The correct answer and explanation is:
Correct Answer: True
The main reason that influenza viruses can cause major outbreaks is because their RNA replicase is error-prone. This is true and is a critical feature of RNA viruses, especially influenza, which contributes significantly to their ability to cause widespread epidemics and pandemics.
Influenza viruses possess an RNA genome and rely on an enzyme called RNA-dependent RNA polymerase, also known as RNA replicase, for replication. Unlike DNA polymerases, this RNA replicase lacks proofreading ability, meaning it cannot correct mistakes made during replication. As a result, errors or mutations frequently occur when the virus copies its genetic material. These high mutation rates lead to antigenic drift, which is the gradual accumulation of genetic changes in the virus over time.
Antigenic drift can cause changes in the surface proteins of the virus, especially hemagglutinin (HA) and neuraminidase (NA). These proteins are the primary targets of the immune system. When they mutate, previously developed immunity, whether through vaccination or natural infection, may become less effective or even ineffective. This allows the virus to infect people who were once protected, leading to seasonal outbreaks and the need for new flu vaccines every year.
In addition to antigenic drift, influenza viruses can undergo antigenic shift, which is a more abrupt change caused by the reassortment of genetic segments between different strains. This process often occurs in animals like pigs or birds, where different influenza viruses co-infect a single host. Antigenic shift can lead to new subtypes that the human population has little to no immunity against, potentially triggering a pandemic.
In summary, the error-prone nature of RNA replicase in influenza viruses leads to constant genetic variation. This adaptability allows the virus to evade immune defenses and cause repeated outbreaks, highlighting the importance of monitoring and updating influenza vaccines regularly.