SHANGHAI, August 20 (Reuters) - China's healthcare system is overly reliant on large, over-burdened hospitals, which will struggle to cope with a spike in diseases linked to the fast-ageing population, the World Health Organization said on Saturday. Even for minor ailments, Chinese patients often shun family doctors or general practitioners in favour of big city general hospitals, a trend that creates often snarling queues and fierce competition for treatment. "As China's health challenges ... continue to mount, with an ageing population, so too will the demands on the country's health system, along with the costs," WHO China representative Bernhard Schwartlander said in a commentary, pointing to rising rates of cancer and cardiovascular disease.