Human immunodeficiency [免疫不足] virus infection and acquired immunodeficiency syndrome [症状] (HIV/AIDS) is a spectrum [系列] of conditions caused by infection with the human immunodeficiency virus (HIV), a retrovirus [逆转录酶病毒].

Following initial infection a person may not notice any symptoms [症状], or may experience a brief period of influenza [流感] -like illness.[4] Typically, this is followed by a prolonged [continuing for a long] period with no symptoms. If the infection progresses, it interferes more with the immune system, increasing the risk of developing common infections such as tuberculosis [结核病], as well as other opportunistic infections [机会型感染], and tumors [肿瘤] which are otherwise rare in people who have normal immune function. These late [晚期] symptoms of infection are referred to as acquired immunodeficiency syndrome (AIDS). This stage is often also associated with unintended weight loss. tuberculosis: 'small lump'.

HIV is spread primarily by sex, contaminated blood transfusions [被污染的输血], hypodermic [皮下] needles, and from mother to child during pregnancy [怀孕], delivery [生产], or breastfeeding [母乳喂养]. Some bodily fluids, such as saliva [唾液], sweat and tears, do not transmit the virus. hypo-: 低于. hypothesis, 光有假说写不了thesis. dermis: 真皮(表皮下面的皮层)

In 2019, about 38 million people worldwide were living with HIV and 690,000 deaths had occurred in that year. An estimated 20.6 million of these live in eastern and southern Africa. Between the time that AIDS was identified (in the early 1980s) and 2019, the disease has caused an estimated 32.7 million deaths worldwide. HIV/AIDS is considered a pandemic [流行性的] - a disease outbreak which is present over a large area and is actively spreading. World War II was the deadliest conflict in human history, resulting in 70 to 85 million fatalities [事故/战争造成的死亡], with more civilians than military personnel killed. Over nine million combatants [作战人员] and seven million civilians died as a result of the World War I.

HIV made the jump from other primates [灵长类] to humans in west-central Africa in the early-to-mid 20th century.] AIDS was first recognized by the United States Centers for Disease Control and Prevention (CDC) in 1981 and its cause - HIV infection - was identified in the early part of the decade.

六级/考研单词: virus, infect, syndrome, spectrum, notify, symptom, influenza, prolong, interfere, immune, tumor, norm, seldom, lump, contaminate, needle, pregnant, fluid, sweat, transmit, hypothesis, thesis, million, outbreak, deadly, civilian, militant, unite