'My mouth started filling with saliva. I couldn't stop and just fell down. Once I finished, I couldn't speak properly. I couldn't get up and move properly. I couldn't really control myself. [It took] a few minutes to get back to my normal state.'

Alexander is one of an estimated 50 million people worldwide living with epilepsy. In Hong Kong, there are roughly 65,000 people (about 1 per cent of the population) with the condition.

Yet, according to Claudia Schlesinger, co-founder and chief executive of Enlighten - Action for Epilepsy, a Hong Kong-based charity dedicated to raising epilepsy awareness and providing non-medical aid to those affected, that's an underestimate.

'There's such a huge stigma associated with epilepsy here in Hong Kong,' she says.

'Sadly, a lot of Chinese believe it's contagious and a curse of the forefathers.'

For a long time, the Chinese term for epilepsy was the insulting deen gan tsing (meaning 'crazy seizure disorder'). It was only in June 2010, after eight years of lobbying in Beijing, that the name was changed to the more appropriate no gan tsing ('brain seizure disorder').

Epilepsy is a brain disorder in which patients suffer from chronic seizures. There are more than 40 types of seizures. Most are caused by electrical brainwaves going haywire. The body responds (although not always) by convulsing, or shaking uncontrollably.

Alexander's second seizure came about a month after the first. By then he'd sought medical advice, but the doctors in Shanghai never diagnosed it as epilepsy.

'Since I was a teenager, they said maybe I was just having one or two random seizures because I was developing,' he explains. 'And they thought I had a tic or something.'

Yet his family was not convinced and saw a child neurologist in Hong Kong.

'We came [here to see her], and that's when I was diagnosed as having epilepsy,' says Alexander, who now lives in Hong Kong. 'We partly came to Hong Kong because of my parents' jobs and partly so we could have a doctor nearby.'

Now, Alexander takes three pills a day, and he has been seizure-free for nearly nine months. That's a huge improvement, since at times, he'd suffer 10 seizures in a month (once he had four in one day). He is very active and competes for Kellett School in several sports. He does not let epilepsy prevent him from living life to the fullest. His friends, family and teachers have supported him throughout his ordeal.

'They understand that I have epilepsy, and we just get on as normal,' he says. 'I've told them what to do if I have a seizure, so they know. They just accept it. They're all fine with it.'

On March 26, designated as Purple Day, or Epilepsy Day, Enlighten will host a campaign to boost epilepsy awareness. Enlighten's Paint the Town Purple campaign will coincide with Epilepsy Awareness Month in Hong Kong.

'Basically it's about making people aware of the colour purple and associating it with epilepsy,' Schlesinger says. 'But it's also about being able to put a colour in place for people to associate visually and help build awareness.'