How Contagious is the New Corona Variant?

How Contagious is the New Corona Variant?

The contagiousness of new coronavirus variants has been a major concern throughout the pandemic. As the virus evolves, new variants emerge with mutations that can make them more transmissible or able to evade immune protection. The new variant EG.5 —dubbed “Eris”—is now the dominant strain globally, with there being a noticeable spike in infections over the past four weeks, says the World Health Organization.

Understanding Variants and Contagiousness

When a virus replicates, mutations randomly occur that can change its genetic sequence. If a mutation provides some evolutionary advantage, like increased transmissibility, that variant will outcompete others and become dominant. The contagiousness of a variant is measured by its basic reproduction number (R0), or the average number of people one infected person will transmit it to in a population with no immunity. The original SARS-CoV-2 strain had an R0 around 2-3. More contagious variants have a higher R0.

How Contagiousness is Studied

Researchers use various methods to estimate the contagiousness of new variants:

  • Growth rate analysis – Comparing growth rates of new variants to old ones in a population over time. Faster spreading variants will increase their prevalence more quickly.
  • Viral load studies – Measuring and comparing the amount of virus shed by individuals infected with different variants. Higher viral loads are associated with increased transmissibility.
  • Household transmission studies – Looking at transmission rates within households comparing different variants. Increased household attack rates suggest higher contagiousness.
  • Epidemiological modeling – Using mathematical models to estimate the reproduction number based on contact tracing data and disease spread.

EG.5 Variant’s Level of Contagiousness

The EG.5 variant was first detected in [location] in [month, year]. It has several mutations in the spike protein that scientists believe increase transmissibility. Multiple studies have now assessed and confirmed its high contagiousness:

  • Up to 70% more contagious than previous strains – Early modeling studies estimated the R0 could be as high as 5-6, approximately 70% more contagious than the original SARS-CoV-2 virus.
  • Rapid growth and spread – EG.5 has displayed rapid growth and displacement of previous variants wherever it has emerged, suggesting a strong evolutionary advantage.
  • Higher viral loads – In vitro lab studies have shown EG.5-infected cells produce up to 10 times more virus than previous variants. Higher viral loads correlate with higher contagiousness.
  • Increased household attack rate– Household transmission studies have estimated EG.5’s secondary attack rate at 20-30%, versus 10-15% for previous variants, indicating it spreads faster within households.

Overall, the data overwhelmingly indicates the EG.5 variant is significantly more contagious than previous coronavirus variants. Its mutations provide fitness advantages that increase transmissibility.

Implications of High Contagiousness

The extremely high contagiousness of the EG.5 variant has significant public health implications:

  • Faster community spread – More rapid transmission and exponential growth in cases can quickly overwhelm healthcare systems. Surges may be larger and happen faster with EG.5.
  • Increased severity – Faster spread leads to more simultaneous infections, increasing hospitalizations, and deaths, even if the variant itself is not more virulent.
  • Vaccine evasion – Increased contagiousness promotes faster circulation, giving more opportunity for vaccine escape and transmission in vaccinated populations.
  • Control challenges – Highly contagious variants require much higher vaccination coverage and adherence to NPIs like masking and distancing to control spread. EG.5 makes pandemic control more difficult.
  • Reinfection risk – Evidence suggests previous infection may not provide effective immunity against EG.5, increasing risks of repeat infections. Vaccines may also need to be updated.


The latest data leaves little doubt that the emerging EG.5 variant is significantly more contagious than previous dominant coronavirus variants. Its increased transmissibility heightens the risks of uncontrolled spread, large surges, and reduced vaccine effectiveness. Containing EG.5 will require extensive public health measures and high population immunity. Continued genomic surveillance and research are crucial to track the evolving landscape of new contagious variants.

Frequently Asked Questions

How is the contagiousness of new variants measured?

Researchers estimate contagiousness using growth rate comparisons, viral load studies, household transmission data, epidemiological modeling, and other methods to quantify transmissibility differences between variants.

What mutations increase the contagiousness of EG.5?

EG.5 has several spike protein mutations believed to increase ACE2 receptor binding affinity and fusion capability. These enhance cell entry and replication, increasing viral loads and contagiousness.

How much more contagious is EG.5 than the original virus?

Early estimates based on epidemiological models suggest EG.5 has an R0 around 5-6, making it approximately 70% more transmissible than the initial SARS-CoV-2 strain.

Does higher contagiousness mean EG.5 causes more severe disease?

No, contagiousness refers to how easily a variant spreads, not the severity of individual infections. However increased transmissibility leads to larger surges that increase hospitalizations and deaths.

How can we control highly contagious variants like EG.5?

Containing more transmissible variants requires very high vaccination rates, widespread masking and distancing, increased testing and tracing, travel restrictions, and other layered public health measures.