If the virus had been capable ofspreading through the air, or if one infected person had unknowingly entered a large population center, Ebola might have become a worldwide epidemic.
Sharing needles among injecting users is one of the primary means ofspreading the HIV virus in Russia, where a hidden epidemic has seen transmission rates spiral.
在俄罗斯，与他人共同使用同一注射用针头是传播HIV病毒的主要途径，疫病暗中流行，传染率不断上升。
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The epidemic is spreading to less well-off places: Mexico has the second-largest share of obese people after America; Guatemala's obesity rate has quadrupled in 30 years.