With news of another virus in the air – how worried should you be?

In the US, a dairy-farm worker develops itching, blood-shot eyes. In Australia, a young girl falls ill after a foreign holiday and is rushed to hospital. In Mexico, another man, already ill and bed-bound, becomes seriously unwell and dies.

Each of these recent cases was caused by a different strain of influenza virus. In each case, it was an animal virus, which should not normally have turned up in humans at all. Should stories like this worry us?

When stories like this hit the news (and for influenza viruses, this happens quite often), journalists write to virologists and ask: how worried are you about this one?

The honest answer is that how any virologist really feels about a story depends on a lot of things, including our personalities: some of us are natural optimists, while others tend to catastrophise. But our professional background does give us an idea of what to look for in a news story about a novel virus. When you next read about a novel virus in the news yourself, these are the questions that can help you decide how much of a worry it might be.

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