Problem 2 - Campbell Biology

Question

Emerging viruses arise by (A) mutation of existing viruses. (B) the spread of existing viruses to new host species. (C) the spread of existing viruses more widely within their host species. (D) all of the above.

Step-by-Step Solution

Answer

(D) all of the above

Step 1: Understand the Term 'Emerging Viruses'

Emerging viruses are those that are newly appearing in the population or have existed but are rapidly increasing in incidence or geographic range.

Step 2: Analyze Each Option

Option (A) suggests that emerging viruses arise by mutation of existing viruses. This is accurate as mutations can create new viral strains that can affect populations differently.

Step 3: Consider New Host Species

Option (B) proposes that emerging viruses arise by spreading to new host species. This is also correct, as viruses adapting to new hosts can lead to new outbreaks (e.g., zoonotic diseases).

Step 4: Examine Wider Spread within Host

Option (C) suggests that emerging viruses can spread more widely within their host species. This option is correct too, as viruses can evolve to become more transmissible within the same species.

Step 5: Conclusion

Given the correctness of options (A), (B), and (C), the appropriate choice must include all these factors. Therefore, the correct answer is (D) all of the above.

Key Concepts

virus mutation

Viruses can mutate, which means they can change their genetic material. This mutation can happen due to errors when the virus replicates or because of external factors such as radiation or chemicals. When a virus mutates, it can create a new viral strain. This new strain might have different properties compared to the original virus, such as increased resistance to medicines or an enhanced ability to infect hosts.
Mutations in viruses are vital for their survival and evolution. They allow the virus to adapt to changing environments and host defenses. For example, the influenza virus mutates frequently, which is why new flu vaccines are developed each year. Understanding virus mutation helps scientists predict and prepare for potential epidemics.

host species adaptation

Host species adaptation occurs when a virus jumps from one species to another. This process is often seen in zoonotic diseases, where viruses jump from animals to humans. For a virus to successfully infect a new host species, it must overcome several biological barriers.
The virus must be able to bind to the host cells, enter those cells, replicate, and then exit the cells to spread the infection. This process can involve several mutations in the virus's genes. Once a virus adapts to a new host species, it can potentially cause outbreaks or pandemics due to the lack of immunity in the new host population.
An example of host species adaptation is the coronavirus responsible for COVID-19, which is believed to have originated in bats and then spread to humans.

virus transmissibility

Virus transmissibility refers to how easily a virus can spread from one individual to another. Factors that affect transmissibility include the mode of transmission (e.g., airborne, bloodborne, contact), the stability of the virus outside the host, and the infectious dose (the amount of virus needed to establish an infection).
Higher transmissibility can lead to more widespread outbreaks. For instance, viruses that spread through respiratory droplets, like the flu or COVID-19, can transmit quickly in crowded or closed environments. This makes understanding and controlling transmissibility crucial for managing public health.
Efforts to reduce virus transmissibility include vaccination, social distancing, and hygiene measures like handwashing and wearing masks. These interventions can help limit the spread of highly transmissible viruses.