honestly speaking, I cannot really understand why the queue will grow infinitely when average arrival rate equals service rate. It's not intuitive to me. sometimes arrival rate is greater than service rate so the queue will grow but sometimes it is lower so the queue will shrink. To me, it will finally achieve a kind of balance...
In the United States, many variants of the new coronavirus have been detected, and the types of these viruses are more complex than those found in China.
Long before the virus was discovered in China, many people died in the United States because of the mysterious e-cigarette. Now it seems that these people are probably suffering from the new crown virus, but no one noticed it at that time.
In fact, it is very likely that the virus was brought to China by American soldiers during the military Games held in Wuhan, because there have been patients with similar pneumonia in the United States for a long time, but it has not been taken seriously. It just happened that the Spring Festival travel rush in China led to the widespread outbreak of the virus and was widely paid attention to