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| |  PAS: Biology of Inhalational Anthrax May Differ in Young and Old Victims By Maggie Schwarz Special to DG News BALTIMORE, MD -- May 7, 2002 -- An inverse association between age and latent period, and a lack of clinical reports of inhalational anthrax in children, suggest that children may be less susceptible to infection by the organism than adults. Anne W. Rimoin, MD, of Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, and colleagues conducted a retrospective analysis of outbreaks of inhalational anthrax and presented their findings here yesterday at the Pediatric Academic Societies annual meeting. In 1979, approximately 7,000 people were exposed in an accidental aerosol release of anthrax in Sverdlovsk, USSR. There were 77 reported cases of infection, all of which were adults (range 24-72 years). Assuming no differential reporting of disease or deaths between adults and children, it appears that no children within the estimated aerosol spore isopleths became ill, hence they may have been less susceptible to an exposure in which at least 2 percent (10/450) of exposed adults became ill. Among reported adults with inhalational anthrax, there is an inverse association between age and length of the latent period (range 2-43 days; p=.001). The mean latent period for patients younger than the median age of 44 years was 23 days compared to 15 days for those 45 years of age or older (p=.015). In the 2001 outbreak in the United States, 22 cases of anthrax were reported; 11 confirmed as inhalational and 11 (seven confirmed, four suspected) cutaneous anthrax. Median ages for cutaneous and inhalational groups were 35 years (range 7 months to 51 years) vs. 56 years (range 47 to 94 years), respectively. The oldest reported victim (94 years) of inhalational anthrax was probably exposed to a very low dose by cross-contamination of mail. This suggests that a much lower dose will cause inhalational anthrax in older subjects, a reflection of possible increased susceptibility. The investigators concluded that the relative lack of clinical reports of inhalational anthrax in children and infants compared to adults might be due to the absence of occupational aerosol exposure of young children, a lack of recognition of the disease in children, or a decreased susceptibility after exposure in children. In Sverdlovsk, they said, assumption of approximately equal exposure by age group suggests that there may be an age-associated susceptibility to inhalational anthrax. In the US outbreak, there was a significant difference in age distribution of anthrax clinical syndromes. Similar to other infectious diseases, the biology of inhalational anthrax in younger versus older populations may differ, they said.
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