on record shows how Eduardo’s working conditions brought on or aggravated the tuberculosis that became the antecedent cause of his death two years after repatriation.   An underlying cause is defined by the World Health Organization as the disease or injury that initiated the train of events leading directly to death, or the circumstances of the accident or violence that produced the fatal injury.30[30] AIDS, described in Eduardo’s death certificate as the underlying cause of death, is a human disease characterized by a marked decrease of helperinduced T-lymphocyte cells, resulting in a general breakdown of the body’s immune system.31 [31] In simpler terms, it is a disease that attacks a person’s immune system, leaving it so damaged that certain diseases (opportunistic infections) or cancers develop. AIDS is the final and most serious stage of HIV infection,32[32] and it takes time for HIV to progress to AIDS.33[33]   According to the Merck Manual of Medical Information, the virus that causes AIDS can only be transmitted in the following ways: (a) sexual relation with an infected person; (b) injection or infusion of contaminated blood; and (c) transfer of the virus from an infected mother to a child before or during birth.34[34] HIV is not transmitted by casual contact or even by close, nonsexual contact at work, school or home. No contact of HIV transmission has been traced to the coughing or sneezing of an infected person or to a mosquito bite.35[35]   30[30] Under international rules for selecting an underlying cause from the reported conditions, every death is attributed to one underlying cause based on the information reported on the death certificate. See: Wisconsin Department of Health Services (http://dhs.wisconsin.gov/wish/main/Mortality/define.htm), last visited on May 28, 2010. 31[31] Webster’s Family Encyclopedia, Volume 1, p. 16. 32[32] HIV is an infection by one of two viruses that progressively destroys white blood cells called lymphocytes, causing Acquired Immune Deficiency Syndrome (AIDS) and other diseases that result from the impaired immunity. 33[33] (http://www.ashastd.org/learn_hiv_aids.cfm), last visited on May 24, 2010; see also The Merck Manual of Medical Information, Pocket Book, Simon and Schuster, Inc. (1997 ed.), p. 927. 34[34] Id. at 927-928. 35[35] Id. at 929.