The incubation period of AIDS is mainly the asymptomatic period, which is a longer period of time, and there are usually no significant changes among the blood tests. However, if it is in the acute phase, it may be accompanied by significant fever and other manifestations in some people due to viraemia. There may also be corresponding manifestations in the blood count, such as a transient drop in lymphocyte count. However, because HIV mainly invades CD4T lymphocytes, which are a relatively small fraction of the overall lymphocytes, its decline is likely not too pronounced. If a lymphocyte subset count is used, it is likely that a significant decline in CD4T lymphocytes can be observed, but this is sometimes more difficult to see if regular review is performed in routine blood tests. There may also be a transient decrease in platelets in the blood count during the acute phase of viremia.