Viruses Are More Dangerous in the Morning: Study

Late-risers finally have their scientific proof that a lie-in can be good for you.

A University of Cambridge study has found that viruses can be up to 10 times more dangerous if they infect patients in the morning, suggesting that it might be a whole lot safer to just stay in bed.

The study, published in the medical journal PNAS on Monday, assessed the effects of infecting mice with either influenza—the virus that causes flu—or herpes—which causes several conditions including cold sores—at different times of the day. It found that mice infected with the viruses in the morning had 10 times higher viral levels than those that were infected in the evening.

Viruses are independent particles that can only replicate by infecting a host cell. Prior to taking over a host cell, viruses lack many properties of living things and so are not considered to be alive. This also makes viruses dependent on hijacking living cells in order to replicate and grow.

The study found that the ability of the viruses to hijack cells varied at different points in the day. The human body follows a circadian rhythm, which is an approximately 24-hour cycle of physiological processes—commonly known as the body clock. This means that different functions of the body—including cell regeneration—vary according to the time of day. The research focused on one gene affected by the body clock—called Bmal1—which has its peak activity in the afternoon in both mice and humans.

When viruses infect patients in the evening, it is akin to someone trying to hijack a factory after the workers have gone home, according to the BBC.

The study also found that disrupting the mice's body clock resulted in them being confined to a physiological state in which the viruses could replicate plentifully. This could have consequences for shift workers, whose circadian rhythm, or body clock, is disrupted by variable working patterns.

One of the study's researchers, Professor Akhilesh Reddy, told the BBC that the findings could have implications for attempts to control viral outbreaks. Examples of recent major viral epidemics include the Ebola outbreak in West Africa—that has killed more than 11,000 people since 2014—and the Zika virus that has now spread to 55 countries and territories since 2015, mostly in Latin America. "In a pandemic, staying in during the daytime could be quite important and save people's lives, it could have a big impact if trials bear it out," said Reddy, a neuroscientist at the University of Cambridge.