The plague - or Black Death - conjures up fearful images. But they are images of the past - when disease control was poor, sanitation terrible and infectious diseases raced through crowded cities. Right? Wrong. Plague is still with us. In 2003, there were 2,118 cases of plague and 182 of those people died. Most of them - 98.7 per cent - were in Africa. But every year and usually in summer, there are cases in our own backyard, particularly on the mainland and Mongolia. Last week, the first warning that plague is back in our region was issued by the Centre for Health Protection, which announced there were five cases in Tibet. Two victims died, giving this small outbreak a death rate of 40 per cent, about what is expected of this highly lethal infection if people do not get treated in time. But we should not panic. While plague is still the same highly infectious, lethal disease that wiped out whole cities in Europe during the Middle Ages and caused mass panic in Hong Kong little more than a century ago, we do have weapons to fight it. First and foremost, we know what causes plague. In fact, in Hong Kong, we should know the most about it because it was here that the organism that causes it - yersinia pestis - was first isolated in 1894 by two scientists. Japanese scientist Shibasaburo Kitasato was the first to announce to the world, in English and Japanese, that he had isolated the organism. But a few days later, Alexandre Yersin, a French-Swiss bacteriologist, said he had isolated the causative organism. There are arguments about who truly discovered it. But it ended up being named after Yersin. We know the organism comes from the fleas that live on rats and other small rodents, some of which are hunted for food on the mainland. Sounds familiar? It's all a bit like Sars. Also like Sars, once plague gets into humans it can spread from human to human in several ways. It can spread by contact with body fluids and also by droplets coughed by people with plague infecting their lungs. This particular form is called pneumonic plague. It was this type that spread and killed very rapidly in Europe during the Middle Ages. So quickly did it spread, scientists of the time thought it was carried by foul mists and fog. However, the most common type is bubonic plague, so called because the plague organism goes to the lymph nodes and multiplies rapidly, causing them to swell and become large, black lumps called buboes. Once these black lumps appear - usually in the groin, armpits, and neck - death was considered a certainty, hence the name the Black Death. But there is one important advantage we have now. Simple antibiotics are effective against plague. But what are the symptoms of the plague? It starts with a fever, headache, aches and pains and exhaustion. Later, the lymph nodes in the groin, neck or armpit swell up, depending on where you were bitten by the flea carrying the plague. If you have those symptoms you are far more likely to be suffering from a viral illness than plague. However, if you have been in an area where there has been a plague outbreak, or where plague is endemic, such as the mainland, Mongolia, Africa, or India, and have been in areas with rat infestations or with bad hygiene, it's important to mention it to your doctor. If you're travelling in places where hygiene is bad, wear long sleeves, trousers and socks to avoid flea bites. Stay away from rat-infested places and maintain excellent personal hygiene, such as always washing your hands before eating or touching your face. Never handle rodents. Lastly, never consider eating or buying exotic animals.