Viruses are more dangerous if the infection occurs in morning, scientists said in a new study. The research published in the Proceedings of the National Academy of Sciences found that if the infection occurred in the early hours of the day, the virus could be 10 times more successful.

The researchers at University of Cambridge when conducting animal studies also found that a disrupted circadian rhythm was more susceptible to infections.

The researchers studied mice that were infected with either influenza or the herpes virus. Influenza causes the flu and the herpes virus causes a variety of illnesses including cold sores. Mice that were infected in the morning had viral levels 10 times greater than the ones in mice infected in the evening.

“It’s a big difference,” Akhilesh Reddy, one of the researchers, told the BBC. “The virus needs all the apparatus available at the right time, otherwise it might not ever get off the ground, but a tiny infection in the morning might perpetuate faster and take over the body.”

Viruses essentially take over the machinery in cells in order to replicate but these cells change dramatically based on the body’s natural clock. Hence, late infections can be seen as the virus trying to take over the machinery after all the workers had already left.

Reddy, a senior fellow at Department of Clinical Neurosciences, University of Cambridge, said that the study’s findings could help in controlling viral outbreaks. “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,” he added.

The study also found that disruptions to the circadian rhythm meant that the body was “locked in” in a state in which viruses are allowed to thrive.

“This indicates that shift workers, who work some nights and rest some nights and so have a disrupted body clock, will be more susceptible to viral diseases,” Rachel Edgar, the first author of the study and a research associate at University of Cambridge, reportedly said. “If so, then they could be prime candidates for receiving the annual flu vaccines.”

The researchers used one DNA virus and an RNA virus for the study. They focused on the Bmal1 clock gene, which works at its peak in the afternoon, both in mice and humans. “It’s the link with Bmal1 that's important, since when that's low [in the morning], you're more susceptible to infection,” Reddy said.