infectivity

noun

in·​fec·​tiv·​i·​ty (ˌ)in-ˌfek-ˈti-və-tē 

plural infectivities

: the ability to produce or transmit infection : the quality or state of being infective

The onset of cough on the second day of illness in this patient, followed by clinical evidence of pneumonia four days later, raised the question of his infectivity during the four days before hospitalization.

—B. Johnson et al.

Even when there are apparently high levels of the virus in the blood, there may be much less infectivity. … a thousand or more of these particles are needed to produce infection.

—Charles Marwick

specifically : the capacity to spread from host to host

The swine flu's infectivity is rated at about 2.5, meaning that every infected person can spread the infection to 2.5 people and it doesn't take a math major to understand that implication.

—Dennis Bloomfield

Examples of infectivity in a Sentence

Recent Examples on the Web

Key Takeaways Infectious disease experts say that COVID-19’s peak infectivity is during symptom onset. —Nick Blackmer, Verywell Health, 11 Dec. 2023

Lower infectivity could mean that BA.2.86 never truly takes off, according to Cao. —Byerin Prater, Fortune Well, 1 Sep. 2023

However, the infectivity of BA.2.86 may be much lower than XBB.1.5 and EG.5. —Byerin Prater, Fortune Well, 1 Sep. 2023

Hull studies the infectivity of Cryptococcus neoformans spores. —Emily Monosson, Time, 11 July 2023

Researchers wonder whether asthma patients’ younger age, fewer comorbid conditions like heart disease or diabetes, or use of inhaled steroids may play a role in modulating SARS-CoV-2 infectivity. —Carolyn Barber, Fortune, 7 Aug. 2020

These mutations are sometimes inconsequential but often impact major viral characteristics including infectivity and immune evasion. —William A. Haseltine, Forbes, 6 July 2022

But infectivity and immune escape are also deeply intertwined, and determining their respective roles in viral spread is exceedingly challenging. —Charles Schmidt, Scientific American, 4 Apr. 2022

To better understand the virus's uncertain future, Wei and other researchers are examining the precise spots in its genome where these mutations are taking place, particularly the places that might boost infectivity and antibody evasion. —Molly Glick, Discover Magazine, 29 Sep. 2021

Word History

Etymology

infective + -ity

First Known Use

1871, in the meaning defined above

Medical Definition

infectivity

noun

in·​fec·​tiv·​i·​ty ˌin-ˌfek-ˈtiv-ət-ē 

plural infectivities

: the quality of being infective : the ability to produce or transmit infection

When sporozoites are incubated with serum from the protected animals, their infectivity is neutralized and prominent deposits of antibody appear over the surface of the parasite …

—Louis H. Miller et al., Science

The onset of cough on the second day of illness in this patient, followed by clinical evidence of pneumonia four days later, raised the question of his infectivity during the four days before hospitalization.

—B. Johnson et al., The Journal of the American Medical Association

specifically : the capacity to spread from host to host

The swine flu's infectivity is rated at about 2.5, meaning that every infected person can spread the infection to 2.5 people and it doesn't take a math major to understand that implication.

—Dennis Bloomfield, Staten Island (New York) Advance