POSSIBLE SOURCE OF EXPOSURE OF CASE 22 TO ANTHRAX SPORES

The origin of case 22 (confirmed inhalation anthrax) has remained a mystery.  There were eight cases of anthrax in New York City, five being confirmed (2, 8, 9, 21, 22) and three remaining suspect (1, 6, 19).  The onset times for each of the eight cases are shown below by color of exposure source, including case 22 which is shown in red.  At least six anthrax-containing letters had either direct or indirect contact with the City of New York.  Two letters were found, two letters remain missing, and two letters had possible indirect contact through cross-contamination (i.e., movement of spores from one letter to another) in a Trenton, New Jersey postal facility. 

In this outbreak, the known incubation period for six of the 11 inhalation anthrax cases was 4 to 6 days.  Assuming the same for case 22, the likely exposure time was October 19-21.  During the exposure time, there were five possible sources of contact between case 22 and anthrax spores.  The first was a letter to the New York Post which was found on October 19 and taken by a policeman from the New York Post office to the New York City Health Department Laboratory.  During this transit, the policeman and two laboratory technicians became infected but did not develop the disease, raising concerns about the handling of the contaminated envelop.  Case 22 may have had contact with the policeman when he was transporting the letter.  The second was a letter mailed to ABC which infected one person but was never found.  The third was a letter mailed to CBS which also infected one person and also was never found.  The fourth and fifth are letters mailed to Senators Daschle and Lahey which at a New Jersey postal facility may in transit have cross-contaminated a letter being sent to case 22 in New York City.  The Daschle letter was found on October 15 and the Lahey letter was discovered on November 16.

For additional speculation on the source of exposure for case 22 (Kathy Nguyen), including a map and interesting trash theory, click here.