44% of secondary COVID-19 cases linked to presymptomatic patients, study suggests

Nearly half of patients who contract COVID-19 from another individual may be infected before that person exhibits symptoms, according to a study published in Nature Medicine. 

For the study, researchers collected throat swabs for 32 days after symptom onset from 94 confirmed COVID-19 patients hospitalized in Guangzhou, China, between Jan. 21 and Feb. 14. They also modeled infectiousness profiles for 77 pairs of infectors and infectees from a separate patient sample. 

Researchers found viral load in throat swabs was highest at symptom onset, which suggests that COVID-19 is most infectious before or at symptom onset. Based on their modeling, which assumed a mean incubation period of 5.2 days, researchers inferred infectiousness started 2.3 days before symptom onset and peaked at 0.7 days before symptom onset.

Researchers also estimated that 44 percent of secondary-case patients were infected from a presymptomatic individual. 

To view the full study, click here.

More articles on public health:
Nearly 60% of COVID-19 chest X-rays look normal, study shows
Social distancing may be needed through 2022, Harvard researchers say
Some providers turn to CT scans for COVID-19 diagnoses


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