Avoid the snails, they're fresh.

One of the attractions of infectious diseases is that there is usually a high turnover of patients. As a general rule, treatment brings about a rapid improvement and patients can return home within a few days, even if they will be receiving on-going treatment for a longer period. My experience at the Hospital for Tropical Diseases has reflected that so far: most patients have been on the wards for only two or three days.
The Viet Anh (Vietnamese-British) ward specialises in neurological infections however, and as such defies the rules. Some patients arrived here before me and unfortunately it looks like they will stay here long after I've left. One of them hasn't moved since my first ward round. He lies on his back, eyes wide open, a ventilator and tracheostomy apparently keeping him alive. The only sign of life is the perpetual twitching of his left cheek, which causes a little foam to form at the corner of his mouth.
A few months ago, he and his twin brother were working in a field outside of Ho Chi Minh City. Pausing for lunch, they noticed the pond nearby was full of snails and didn't think twice: a few raw gastropods and back to work. Unfortunately, the snails were carrying the roundworm Angiostrongylus cantonensis. This parasite usually lives in the lungs of rats, but regularly makes excursions to their gut. Once excreted into the open world, it then relies on snails and slugs to ingest it so that it can develop into new, fully-infective larvae which can colonise new rats.
As is often the case with such worms, humans are only an "incidental host" (see Half a Brain). They become infected by eating raw or under-cooked snails and slugs, or vegetables contaminated by them. Having invaded a new host (be it a human or a rat), Angiostrongylus travels first to the brain and causes an inflammatory reaction which is characterised by the presence of a specific type of white blood cell: this is eosinophilic meningitis, and this is what brought our two brothers into hospital.
Though they both suffered from headaches, nausea and vomiting, neck stiffness and the occasional seizure, only one of them had read the textbook. He got better after a fortnight, and returned home. His brother, however, slipped into a coma and he is still there now. Most patients with eosinophilic meningitis make a full recovery; it is extremely rare for it to cause brain damage as it has in this case.
At this stage, after such a long coma, there is little cause for optimism. He may yet make a miraculous recovery, but it is unlikely. His family will eventually have to decide whether they wish to keep paying for him to receive supportive treatment in hospital, or whether they would rather he came home and were released from his bodily prison.
His brother, with whom he shares so much, reminds us that when two similar people are infected with the same parasite, the outcome can still vary enormously. We still have a lot to learn about the factors which dictate who will be the lucky ones. And we still have a mountain to climb in order to prevent poor, hungry people from eating a quick, easy and free lunch.

A Missed Opportunity

In the ICU today, a young girl lies unconscious. Oblivious to the crowd of doctors in the room, she is being kept alive by a ventilator and a feeding tube. She looks very peaceful, as sleeping children often do, but this belies the events going on in her head.
About 14 days ago, she was bitten by a mosquito of the Culex family. Young girls are not normally the target of Culex mosquitoes: they tend to go more for pigs and wading birds, which are the main reservoirs for Japanese Encephalitis Virus (JEV). However, every now and then, humans get bitten. This particular mosquito was carrying JEV and unwittingly transmitted it to our patient. She subsequently developed a fever, headaches and became nauseous. She fitted and then began to lapse into a coma. And now she is in our ICU, fighting for her life.
Only 1% of JEV infections cause encephalitis, accounting for some 50,000 cases annually. Unfortunately though, the outcome when it happens is terrible: 30% die; 30-50% survive, but with irreversible brain damage; and less than 30% make a complete recovery. The only antiviral treatments which exist have been shown to be useless in Japanese encephalitis - all we can do is wait and hope that she is in the minority which pull through.
It is terrible to see a young girl who may well die or be left brain-damaged by a childhood infection. What makes it worse is that Japanese encephalitis is a preventable disease. While the two vaccines offered to travellers are not ideally suited to mass immunisation programmes in the region, a Chinese vaccine has shown great promise. Several trials have shown it to be particularly effective in children, who are the main victims of JEV. Why it has not yet been incorporated into regional vaccination programmes is not clear to me, but it certainly appears to be a missed opportunity.
There are plenty of excellent vaccines out there which have the potential to prevent millions of childhood deaths every year. Most of them are not expensive to produce: the main challenge is making them available to the people who need them, and ensuring that as many people are immunised as possible. At the moment it seems we're investing far more in inventing new treatments than we are in using those that already exist.

TB or not TB?

I've always thought of tuberculosis as a disease of the lungs. I won't pretend that it's because of La Traviata and her persistent coughing which punctuates Puccini's work. Even after three and half years of medical school, I couldn't help associating TB with coughing, weight loss and a few other symptoms.
Of course, this isn't wrong: the lungs certainly are a site of predilection for Mycobacterium tuberculosis. It likes to set up camp there and hibernate for years, sometimes a whole lifetime. But despite this affinity for the draughty recesses of the chest, TB also enjoys going for a wander elsewhere. The spine, the kidneys, the eyes: no sites are really off limits for this bacterium if the conditions are right.
The conditions are definitely right in this patient. He contracted HIV many years ago and has not been receiving any antiretrovirals. Slowly, but surely, the virus has gained the upper hand over his immune system. Today, his body is essentially a very badly defended shelter for whichever micro-organism might choose to invade.
He came in to the hospital because he was having difficulty walking. On examination, he is weak all along his right-hand side. He has swollen lymph nodes throughout his body, along with headaches and fever. This picture is typical for toxoplasmosis, but the doctors here are convinced it will turn out to be TB in the brain. There's so much of the disease around, the investigations will probably prove them right.
A few weeks ago I would never have associated TB with hemiplegia, particularly if the patient didn't have any chest symptoms. Perhaps someone could have guided me there with some leading questions, but the two things just weren't linked in my mind. Having now seen nearly a dozen cases of TB meningitis, I'm starting to realise that most things could be due to this disease.

Scared of Air

The first thing I noticed about this patient was how well he looks. In an ICU full of emaciated, jaundiced and comatose patients, he stands out because he seems fine. He's fully conscious and notices us as we come to stand at his bedside, looking down at him. He begins to talk to Dr Nguyen - perhaps he's asking how much longer he has to stay here. He smiles and laughs, and then returns to his thoughts while we examine him.
His bed is oddly placed within the ward. He's not lined up with the other patients in the bays; instead he lies in the middle of the ICU despite there being ample space elsewhere. We probe Dr Nguyen for answers. "Afraid", he says, in very broken English. "Afraid, er, of... of wind". This doesn't make sense to me - I must have misunderstood. But Dr Nguyen illustrates the point: taking his notepad in his hand, he waves some air into the patient's face. Suddenly, everything changes. A terrified look is in the patient's eyes, and he draws in a sharp breath, as if he's seen a ghost. A few seconds of wide-eyed stares; and he's back to normal. Looking calmly around the bed, breathing quietly. He asks Dr Nguyen another question.
The look of terror that overcame our patient is probably matched only by the look of amazement on my face. "He's afraid of air?" I ask, still skeptical despite the obvious demonstration. Dr Nguyen repeats the process. Again, the patient gasps as soon as the air reaches him. The fear in his eyes is unlike anything I've ever seen before. And then it's gone again, melting away almost instantaneously.
That's it. That's all there is to see in this patient. He was brought in to the hospital this morning, because of his strange behaviour. His bed is strategically placed to avoid the drafts from the two large air conditioning machines: they would be unbearable for him. On questioning, it emerges that he was bitten by a dog two months ago.

Fear of air and water are pathognomonic for rabies: no other disease produces these symptoms. And while he may look well between the flashes of terror, he will be dead in a matter of days. Just as there is no doubt about the diagnosis, there is no doubt about the outcome: once symptoms appear, the mortality rate is 100%. An urgent course of vaccinations after the bite might have saved his life, but it is too late now.
For the past two months, the virus has been slowly making its way through his nervous system and up to his brain. Once there, the virus begins to replicate and then spreads back out via the neurones to most organs including the heart, eyes and kidneys. Signs and symptoms then begin to appear, including paralysis, confusion, agitation and the tell-tale phobias. The salivary glands are hijacked, churning out millions of virus particles in the hope of infecting a new host.
Patients with rabies don't usually stay in the hospital very long. Once the diagnosis has been explained to the family, patients are usually taken home: there is no point paying for medical treatment when it can ultimately do nothing for the patient.
Before leaving the ward, I take a last look at him. He still looks very well. The calm before the storm.