COVID-19 viral loads peak early

Patients' SARS-CoV-2 viral load is highest within five days of their first symptoms. This underscores the need for early isolation to prevent transmission.

SARS-CoV-2, the virus that causes COVID-19, is transmitted from person to person through close contact. Therefore, understanding the SARS-CoV-2 viral load is critical to expanding knowledge and understanding transmission patterns.

Dr. Muge Cevik, of the University of St. Andrews, UK, used existing research studies to review ninety-eight studies of coronavirus to determine when patients' SARS-CoV-2 viral loads are highest and therefore most effective at transmitting the virus.

79 of them focused on SARS-CoV-2 and the rest on SARS-CoV-1 and MERS-CoV. The majority of the SARS-CoV-2 studies only included hospital patients. The results were published in the journal Lancet Microbe.

Dr. Cevik's study found that patients with COVID-19 had the highest amount of live virus in their upper respiratory tract within the first five days after symptoms appeared. The highest amount of virus in SARS and MERS is observed in the second week for signs and symptoms. Despite the results of a high SARS-CoV-2 viral load, no study isolated the live virus beyond the ninth day after the first symptoms of COVD-19.

The researchers concluded that patients with COVID-19 infection are most contagious early on, especially when peak viral loads occur around the onset of symptoms by day five. These results underline the importance of immediate isolation with symptoms occurring early in the course of the disease. With potential delays in patient isolation, effective COVID-19 containment can be challenging, even with an early detection and isolation strategy.

Reference:

Cevik M., Tate M., Lloyd O., Maraolo AE, Schafers J., Ho A. SARS-CoV-2, SARS-CoV and MERS-CoV dynamics of viral load, duration of virus shedding and infectivity: a systematic one Review and meta-analysis. Lancet Microbe, 2020. doi.org/10.1016/S2666-5247(20)30172-5.

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