Emerging and re-emerging viruses are a significant focus of study in virology, given their ability to cause widespread disease and adapt to new hosts, including humans.
Emerging Viruses
Emerging viruses are those that have recently appeared in a population or have existed but are rapidly increasing in incidence or geographic range. Some factors contributing to viral emergence include:
- Zoonotic transmission: Viruses jumping from animals to humans (e.g., SARS-CoV-2, Ebola).
- Environmental changes: Deforestation and climate change can alter habitats, bringing humans into closer contact with new viral reservoirs.
- Globalization: Increased travel and trade can spread viruses across regions quickly.
Examples of Emerging Viruses:
- SARS-CoV-2 (COVID-19): First identified in 2019, this coronavirus caused a global pandemic with extensive health, social, and economic impacts.
- Nipah Virus: A zoonotic virus transmitted from bats to humans, causing severe respiratory and neurological symptoms.
- Zika Virus: Emerged in Brazil in 2015, leading to severe birth defects when pregnant women were infected.
Re-emerging Viruses
Re-emerging viruses are those that were previously under control but are now increasing in incidence or geographic distribution. Factors include:
- Vaccine hesitancy: Declines in vaccination rates have led to the resurgence of diseases like measles.
- Antiviral resistance: Viruses can evolve resistance to treatment, making them harder to control.
- Urbanization: Rapid growth of urban areas can create conditions favorable for viral spread (e.g., overcrowding, poor sanitation).
Examples of Re-emerging Viruses:
- Dengue Virus: Mosquito-borne virus that has re-emerged in many tropical regions due to increased mosquito populations and urbanization.
- Measles: Once nearly eradicated, but resurgence has been linked to declining vaccination rates.
- Yellow Fever: Periodic outbreaks, especially in regions with fluctuating immunity levels and mosquito control challenges.
Genomic Surveillance
Genomic surveillance is crucial for detecting new variants of both emerging and re-emerging viruses. By tracking mutations and changes in viral genomes, scientists can better understand how viruses evolve, spread, and respond to control measures, which is essential for developing vaccines and treatments.