A British adventurer faces going blind after contracting a potentially deadly infection while trying to visit every country in the world.

David Simpson, 38, had already visited 150 countries before picking up latent tuberculosis in South Asia.

The Belfast local said the illness began attacking his left eye, causing flashing lights and blurred vision and forcing him onto powerful medication and immunosuppressants as doctors tried to stop it getting worse.

'I've done a lot of travelling in South Asia last year and I ended up contracting latent TB, which is a non-contagious form of tuberculosis (TB),' he said.

'So it was actually attacking the eyesight of my left eye. So I noticed that whenever I was watching TV there was a blur, a flashing light in my eye.'

As his symptoms worsened, Simpson cancelled travel plans and was forced to isolate because his suppressed immune system left him vulnerable even to minor illnesses.

'Eventually they diagnosed and they seen it was latent TB,' he said.

'I had to cancel my round trip. I had to isolate from people because I couldn't contract colds or flus because my immune system is a bit hacked in terms of combating those issues.'

The normally restless traveller, who usually goes away five or six times a year, said the sudden confinement was hard to deal with.

'For somebody who goes away so often every year, not being able to socialise with more than maybe three or four people was difficult to manage,' he said. 

'I wasn't able to go out for dinner in restaurants or cafes or anything like that, it was quite difficult.' 

Simpson said doctors warned that, had the infection not been caught in time, he could have lost the eye altogether.

At one point he was taking 25 tablets each morning to try to control the inflammation. 

'If I didn't catch it, it would have taken my eye,' he said. 

'We're not yet off the medication, so hopefully I will know within the next 4 to 6 weeks if I'm out of it without losing my eyesight.'

Even if the infection is fully suppressed, some of the damage is permanent and Simpson says he will never regain full sight in his left eye.

'The issue now is I won't get that eyesight back. I've got partial loss in my left eye and that's permanent,' he said.

'The main thing is stopping it getting worse, because if it moves into my direct line of vision, then we'll have bigger issues.

'If I look at you with my bad eye, I see much less than half your face. The rest is grey.' 

Despite the ordeal, Simpson said he still has no regrets about the trips that brought him there.

'If someone had told me before one of these trips that I'd lose partial vision in one eye, I'd probably still have gone,' he said.

He said the experience had also made him realise how devastating total blindness would be.

'People said they'd rather lose a leg, even two, than their eyesight. For me, it would mean I couldn't keep having the same experiences,' he said.

Simpson believes he caught tuberculosis simply by being near someone infected while travelling, comparing its spread to Covid.

'If you're within a certain distance of someone with TB, you can catch it. It could be as simple as being on a flight. I was in South Asia, where it's a huge issue,' he said.

Although his TB is currently latent and non-contagious, he said the concern is that it could become active.

But he plans to return to travelling as soon as doctors give him the all-clear, including to destinations many tourists avoid.

Simpson has visited more than 150 countries, including Pakistan, Afghanistan, Ukraine and Russia, and said there are few places he would refuse to go if he had the right contacts.

'Everywhere is possible to visit,' he said. 'I could go to Iran now if I wanted. It just depends on getting the right person to take you.'

In higher-risk regions, he relies on trusted local guides and contacts on the ground.

'There's a network of contacts who can get you into these areas,' he said.

'The situation changes quickly, but they have eyes and ears on the ground in difficult regions.'

While he would not take unnecessary risks alone, he admitted he always weighs the danger against the experience.

'I know some people who go on their own. I probably wouldn't. I feel I've got too much to lose. Everyone has. You look at the risk and reward,' he said.

The property developer said his goal of visiting every country began around 2015 after he took two years off work and travelled to around 70 or 80 nations.

'I realised how much of the world I still hadn't seen, so I set myself the goal of visiting every country,' he said.

Born and raised in Belfast, he typically travels five or six times a year around his full-time job, though he has remained at home since Christmas while battling to protect his sight.

One of his most memorable trips was persuading his father, now in his 70s, to join him in Pakistan.

'I told him England were playing cricket there. That was the carrot,' he said.

They flew into Karachi, visited slums, took an overnight train and attempted to enter Baluchistan before being turned back by authorities.

'We were asked to go back to Karachi,' he said.

'It's a huge, mountainous and desolate region. It's basically a free-for-all for al Qaeda.'

Despite the health scare and the dangers involved, Simpson remains determined to finish what he started and visit every country in the world.