By Emma Farge and Jennifer Rigby GENEVA/LONDON (Reuters) -Developing nations are lobbying for fairer access to treatments than they got during COVID-19 as global talks begin on drafting new health rules for combating pandemics. But they worry that the odds of a favourable outcome from a scheduled 18 months of negotiations at the World Health Organization (WHO) are already stacked against them, as they lack the negotiating firepower of wealthier countries. South Africa, Pakistan and India were among countries that made formal requests during an initial three days of talks, which ended on Wednes…