Humans are not considered part of the natural transmission cycle; their infection is accidental.

人类并未被考虑为自然传播周期的一部分，其感染是偶然发生的。

youdao

There is no present evidence that domestic cats play a role in the transmission cycle of H5N1 viruses.

目前没有证据表明，家猫在H5N1病毒的传播链中发挥了作用。

youdao

To date, only domestic poultry are known to have played a role in the transmission cycle of the virus from animals to humans.

迄今为止，已知只有家禽在病毒从动物传给人类的传播循环中发挥作用。

youdao

We've tried to kill mosquitoes with insecticides, tried to break that transmission cycle.

NPR: Altered Mosquitoes May Save Humans From Malaria

Vaccination campaigns need to treat everyone who comes in contact with an infected individual in order to break the cycle of transmission.

FORBES: Despite the Odds, Vaccinators Triumph Over Polio

With the car transferring power to the ground through a single-clutch mid-rear transaxle, the Vanquish doesn't cycle through gear ratios with quite as much impact as a car with a dual-clutch automatic manual transmission, the Ferrari V12, for instance, which also enjoys a 165-hp advantage.

WSJ: 2014 Aston Martin Vanquish Review: No, Mr. Bond, I Expect You to