Undetected cases drive spread in communityDate: 21 March 2020 Tags: Disaster & Disaster Management
Eighty-six percent of people in China who were infected with novel coronavirus (SARS-CoV-2) were not tested in the two-week period before travel restrictions came into force on January 23 in Wuhan and other cities. And these undetected cases contributed to the majority of virus spread in the community, according to a study.
The researchers used a computer model that draws on observations of reported infection and spread within China in conjunction with mobility data from January 10-23 and January 24-February 8.
- People who experienced mild, limited or no symptoms were not detected but spread the virus anyway. About half as infectious per person as a documented case who has more severe symptoms and maybe shedding more.
- Even though the undetected cases are only 55% contagious compared with those who exhibit severe symptoms and are detected, due to their greater numbers, they facilitated the rapid spread of the virus throughout mainland China. The undetected cases were the source of infection for 79% of documented cases.
- The undocumented infections which tend to be milder are distributing the virus broadly. They’re contributing essentially to what is called self transmission of the virus because it’s really undetected and it’s flying below the radar.
- The modeling study suggests that a “radical increase” in identifying and isolating people who have not been tested yet would be needed to fully control the spread of the virus.
- The paper says that steps taken by many individuals and governments to restrict travel, shut down schools, prevent large gatherings, isolation of suspected cases, and the use of face mask and regular handwashing could have helped slow down the spread of the virus. And some countries have also started community testing.
- The authors say that while travel restrictions and other control measures could have reduced the spread of the virus in the community, the study does not provide evidence that such control measures would be sufficient to end the spread locally and prevent a rebound once travel and other restrictions are removed or relaxed.
The paper concludes by saying that there are already four coronavirus strains that are circulating in the human population. And if the novel coronavirus follows the pattern of H1N1, then it would spread globally and become the fifth coronavirus to become endemic in the human population.