Chinese scientists have shown in a study on how easily the SARS-CoV-2 virus can jump from one person to another in some 'secret' transmission that can be far from anyone's control.
In their study published in Nature Medicine, 94 people who tested positive for the coronavirus were recruited. Each person's viral load was regularly measured using a cheek swab. It was the criterion they used for up to 21 days to tell how aggressively the virus had multiplied into their cells.
Findings showed that the viral loads tended to peak soon after the showing of symptoms. It then gradually decreased until after 21 days, when the virus could no longer be detected.
Additionally, the researchers also gathered information on 77 situations in which a patient was likely to transmit the virus to another person. Previous studies have led to the belief that the lag time between initial exposure to the pathogen and the first sign of illness was just a little more than five days.
When the data was collected altogether, researchers were able to come up with an estimated period of two to three days straddling the first signs of illness, in which a person appeared to be highly contagious. Within seven days, their ability to spread the virus quickly declined, the study revealed.
Furthermore, the scientists calculated that for every 100 cases of coronavirus infection, about 46 to 55 of them could be traced back from a presymptomatic spreader. That's almost 1 in 2.
The Dreaded 'Asymptomatic Spread'
An asymptomatic spread happens when people unknowingly spread the virus, thinking they are not sick due to the absence of symptoms. An infected person can walk around feeling fine for more than two days while unknowingly scattering the virus everywhere, planting seeds for future infections.
Unless the asymptomatic spreader is wearing a mass, that person could already be spreading the coronavirus to grocery cashiers, workers at the local pharmacy, or to health care workers at the hospital.
Maria Van Kerkhove, the World Health Organization's health emergency coordinator, recently approximated that 75% of people who test positive for coronavirus but are asymptomatic at the time of testing will eventually become sick and develop symptoms.
Researchers from the Centers for Disease Control and Prevention and the Washington State Public Health Laboratory took a tally on the residents of a nursing home in King County, Wash. They found that 13 residents of the said facility tested positive for the coronavirus, even though they displayed no symptoms.
A week later, when the researchers did a follow-up, 77% of those who tested positive were already experiencing symptoms of COVID-19. Researchers assume that the mobility of the ten presymptomatic residents might have contributed to an infection rate that reached about 30% of the facility's residents.
Testing is Crucial
The new findings highlight how coronavirus testing is crucial at this point. Testing that is widely available, reliable, and gives back quick results is what scientists are hoping for.
Scientists believe that if the goal is to prevent new outbreaks, tests need to identify at least some people who are carriers of the virus while they still feel fine. If people become aware that they are silent carriers of the virus, they could be required to stay isolated at home and refrain from direct contact from other people.
Dr. Ashish Jha, the director of the Global Health Institute at Harvard University, claims that the only way to know who is sick and to pull them away from the uninfected effectively is testing.
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