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The time of infection affects the severity of viral infections


The time of day affects the severity of a virus infection
According to a new study, the time of day plays an important role in the severity of viral infections. The study by British scientists shows that herpes viruses multiply much faster in mice when the animals become infected at the beginning of their resting phase.

The time of infection affects the severity of an infectious disease
Although every person can become infected with countless pathogens, some tend to get sick, while others almost never. This is partly due to the fact that some people are more susceptible to infections. For example, because her immune system is weakened due to a lot of stress or an unhealthy diet. The severity of an infectious disease is not the same for all patients. Why this is so could possibly be due to the timing of the infection, as British researchers have found.

Heart attack risk depending on the time of day
Various studies have already shown that the time of day has an impact on human health. For example, US researchers reported that the risk of heart attack depends on the time of day. And according to Spanish scientists, a heart attack is worse in the morning than in the evening. A British team of researchers has now found that the time of day plays an important role in the severity of a viral infection. Her investigation shows that herpes viruses multiply drastically faster in mice if the animals become infected at the beginning of their resting phase.

Shift workers are more susceptible to diseases
As the team led by Professor Akhilesh Reddy from Cambridge University in the UK wrote in a statement from the university, the discovery could partly explain why the time of day also plays a role in vaccinations, why shift workers are susceptible to diseases or why infectious diseases are more likely to occur in winter. "Infection at the wrong time of day could cause a much more severe acute infection," the study authors said.

Pathogens multiply significantly more at the beginning of the resting phase
The results of the investigation were published in the "Proceedings" of the US National Academy of Sciences ("PNAS"). As the news agency dpa reports, the scientists initially infected mice with the herpes virus MuHV-4 through the nose at different times of the day. It was shown that at the beginning of the resting phase - in the morning in the case of nocturnal rodents - the pathogens multiplied about ten times more than when the active phase was infected.

In contrast, the time of day did not affect the infection process in genetically modified mice lacking Bmal1 - a key gene for the internal clock. "If we disturbed the body clock in mice, the timing of the infection no longer mattered," explained lead author Rachel Edgar. "The viruses multiplied constantly."

Viruses may affect the cell clock
The severity of an infection in cell cultures also depended on the respective daily phase. However, in cells without the Bmal1 clock gene, the herpes viruses multiplied at a similar rate at all times. It is said that further experiments even indicated that the viruses actively influenced the cell clock in order to be able to develop optimally.

When the researchers then tested the multiplication of flu viruses on cells, they came to a similar conclusion. "The similar effect of cellular arrhythmia on two different, clinically important virus families shows that the internal clock and its special components such as Bmal1 have a broad impact on viral infections," the authors explained.

Diseases more often in winter
This effect could possibly even contribute to epidemics. For example, the clock gene Bmal1 is less active in humans in the winter months. "We speculate that this can contribute to the spread of viruses at the population level, because many viruses such as influenza are more likely to cause infections in winter," said the researchers. However, there could be other explanations for this.

Scientists from Cambridge University reported last year in the journal "Nature Communications" that our immune system changes with the seasons. According to the experts, their discovery offers a possible explanation for the fact that certain diseases occur more often or worse in winter and that people tend to stay healthy in the summer months.

Flu shot in the morning more effectively
According to the study authors, the results of the current study could also explain why shift workers whose body clocks are disturbed are susceptible to chronic diseases, possibly also to viral diseases. In addition, the effectiveness of vaccinations could depend on the time of day. This was recently pointed out by a study in people aged 65 and over.

The team led by Anna Phillips from the British University of Birmingham reported in the journal “Vaccine” that flu vaccinations in the morning compared to those in the afternoon boosted the production of antibodies more within a month. (ad)

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