New COVID research shows novel variants have shorter incubation periods

The incubation period of newer variants of COVID-19 is getting shorter, down from about five days to a little over three, changing the isolation period for people who have contracted the virus.

A study published in the Journal of the American Medical Association (JAMA) analysed 142 studies and found the average incubation period of SARS-CoV-2 shortened with the evolution of new variants. The authors, from Beijing’s Peking and Tsinghua Universities, write: “The incubation periods of COVID-19 caused by the Alpha, Beta, Delta, and Omicron variants were 5.00, 4.50, 4.41, and 3.42 days, respectively.”

The JAMA study examined papers between December 1, 2019 and February 10, 2022. Combined, the studies included 8,112 patients.

The paper says: “Incubation period is one of the most important epidemiological parameters of infectious diseases. Knowledge of the disease’s incubation period is of great significance for case definition, management of emerging threats, estimation of the duration of follow-up for contact tracing and secondary case detection, and the establishment of public health programs to reduce local transmission.”

As COVID-19 continues to spread around the world, staying safe and up to date with health advice is still critical. More than 80% of Australia’s 13,369 deaths due to COVID (at the time of writing) have been recorded in 2022 alone.

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“Identifying the incubation period of different variants is a key factor in determining the isolation period,” write the authors.

The researchers note some limitations in their study. In most cases, data was collected retrospectively resulting in uncertain exact dates of exposure. They also cite the variability in the data used to determine the average incubation period, and the small number of studies looking at the incubation period caused by different SARS-CoV-2 strains. This small data set necessitated a “cautious” generalisation of the results as small deviations in incubation time in people of different ages and sexes, for example, are not clear in the data.

However, the study did find that the mean incubation period in children was shorter than in the general population. The results also note that “children can be a source of transmission during the viral incubation period.”

While kids often don’t have as severe immediate health effects from the virus, there are signs that COVID may be leaving its mark in the longer term.

A study published in JAMA Pediatrics looked at lingering symptoms four weeks after children were infected with COVID-19. The research into Long COVID in kids came out of the University of Colorado in the US.

Read more: The impact of COVID-19 on mothers and young people revealed

The researchers looked at the health records of 660,000 children, nearly 60,000 of whom tested positive for COVID-19 between March 1, 2020 and October 31, 2021.

In their findings, the scientists noted the most common lingering symptoms four weeks after an initial positive test were loss of taste or smell and myocarditis.

Younger kids with other health conditions who were severely unwell with COVID-19 were at the highest risk of lingering health problems a month after infection.

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