What caused Angela Merkel's violent shaking?

German Chancellor Angela Merkel is nothing if not a worker. Despite having held Germany’s highest office for the past 14 years, she barely ever shows signs of stress and is known among colleagues for rarely, if ever, taking a sick day.

Which made it all the more concerning when Merkel was filmed visibly shaking during a military ceremony welcoming the new Ukrainian president to Berlin on Tuesday.

Merkel’s team was quick to brush off any fears about the Chancellor’s ill health. In a press conference after the ceremony, she suggested that it was all due to dehydration. “I’ve drunk three glasses of water in the meantime, clearly that was what caused it. And in that respect I’m doing much better,” she said. Colleagues were quick to point out that Germany is in the middle of a serious heat wave with temperatures reaching 30 degrees centigrade.

Dehydration can cause various serious problems as the body is two thirds water, and requires water for most basic functions. Usually you can spot dehydration early: it can lead to headaches, fatigue, and dark coloured urine. If you ignore these warning signs, dehydration can eventually lead to heat stroke, kidney problems, seizures, low blood volume shock, and eventually organ failure and death.

As is usually the case when politicians exhibit any kind of illness, online commentators have descended on Merkel, with alternative explanations ranging from the unlikely (she might have Parkinsons; you'd see a slower, less pronounced shake emanating from one side of the body) to the truly ridiculous (she hates her own country’s national anthem and couldn’t bear to listen to it.)

While these theories are almost certainly nonsense, Dr Mike Fitzpatrick says there could be something more to it than simple dehydration.

“I watched the video and thought it was very strange. It’s a really pronounced tremor isn’t it? There’s also a second video where you see her shaking and then moments later she walks away and looks completely fine, it was very strange.

“I read that there’d been some mention of dehydration but I don’t think it looks like that to me. You wouldn’t normally get shaking like that with dehydration. If you were starving, maybe, but thirst wouldn’t do that to you.”

Dr Fitzpatrick is mystified by the idea that Merkel says she was fine after a couple of glasses of water. “Honestly, to me it looks like an infection. Sometimes when you have an infection, you’ll find the body will shake.” Such rigors are caused by a fever: when the body experiences a sudden increase in temperature, the sufferer will feel like they’re freezing and start to shiver very intensely.

The function of rigors is the same as shivering in the cold: the body is trying to heat itself up. In this case though, rather than trying to heat itself up to stay warm, the body is trying to heat itself up to burn a bacterial infection out of the body. Chemicals called pyrogens in the blood affect the hypothalamus in the brain, the body’s internal thermostat, which in turn causes the body to activate its immune response and heat up rapidly.

“Rigors tend to last a few minutes and then once the heat is generated, you’d be right back to normal, which is what seems to be happening in this video of Merkel,” explains Dr Fitzpatrick. “She’s fine when she walks away."

Dr Fitzpatrick concedes that there could be more serious causes, but says he finds the other options very unlikely. “I suppose there are a few other options. It could be malaria but it seems pretty unlikely Merkel would have caught that in metropolitan Germany. Alternatively, I suppose it could be a panic attack, but that would be a very unusual presentation for a panic attack, and it doesn’t seem very Merkel-like to be having a panic attack at a state event; she’s been Chancellor for 14 years, so she’s got plenty of experience with these kinds of things.”