In a tetanus infection, out of all symptoms and signs, why is respiratory problems and muscle spasms the main concerns of doctors?

See answer: The severity of Tetanus varies depending on the amount of toxin that reaches the nervous system, the duration between initial infection and first symptoms(symptoms can develop in 2 days or as long as 38 days after infection....the shorter the interval the more severe the disease). Muscle spasms cause the respiratory failure, which is fatal if not treated.