One of the world’s top infectious diseases experts has compared scientists who predict the spread of Covid-19 to stock market traders.Professor Johan Giesecke, Sweden’s former chief epidemiologist, warned that long-term forecasts on how the virus would rip through the UK were “way off the mark”.The World Health Organisation adviser said First Minister Nicola Sturgeon and Prime Minister Boris Johnson had been “leaning too much” on modelling forecasts.The 70-year-old said the UK should have tackled the coronavirus outbreak by copying his country’s approach – shielding the elderly while allowing businesses to operate.He said that ordering the public to wash their hands and observe social distancing rules was the best way to fight the killer