Is it just your time to get flu?
From vitamin C and Echinacea to warm clothes, there’s no shortage of ideas about how to prevent colds and flu. Many of these are not based on solid scientific evidence. Medical researchers are only starting to unravel the range of factors that affect our susceptibility to getting an infection. Now we have discovered that our body clock makes us more prone to get infected at certain times of the day.
It is perhaps easy to forget that we have coevolved on this planet with micro-organisms such as viruses that cannot copy themselves without help from our cells. So what happens when a virus encounters a cell? First, it has to get in through a protective barrier, the cell membrane. Then it has to hijack the interior of the “host” cell to subvert it and divert all resources to copy itself millions of times. Once an army of identical clones is formed, it breaks out of the cell. But that’s only if the virus has its own way.
Our immune system will invoke mechanisms to stop the i nvading organisms from entering, replicating and spreading. This defence system works at t he level of individual cells in the body, but also in specialised tissues of the body that are designed to mount a response to such invasions.
It now turns out that our body clock is also an important gatekeeper of virus infections. The body clock is an amazing piece of evolutionary biology. It’s thought that most organisms on our planet have a biological clock that keeps track of the 24-hour day. It can do this by orchestrating chemical reactions and genetic switches that rhythmically control thousands of genes in chromosomes in the cell — turning about 15% of all genes on and off across the day and night.
So why might viruses care about our body clock? Because our cells are miniature factories, making things that the virus must copy itself, the virus is less likely to succeed when the production line is shut down.
We found, by laboratory testing, that viruses are less able to infect in the late afternoon. In the early morning, our cells are hives of biosynthetic activity so, if a virus tries to take over a cell in the early part of the day, it is far more likely to succeed, and spread faster. Perhaps even more interestingly, when the clockwork is disrupted, viruses are more successful in taking over cells and tissues. This can happen when we do shift work or get jet-lagged.
The research could also help us crack a longstanding enigma: Why do virus infections such as flu happen more commonly in winter? It turns out that the very same molecular switch, called Bmal1, that goes up and down in the day and night also changes according to the seasons, going up in the summer and down in the winter. When we artificially lower Bmal1 levels in mice and cells, the virus is able to infect more.
If you’re desperate to avoid catching flu, rather than trying to boost your immune system with various vitamins, you may want to try to work from home in the mornings.