PART I (time to completion: 50 minutes)
On October 31, 1989, the state health department in Louisiana was notified by two physicians in Bogalusa, Louisiana, that over 50 cases of acute pneumonia (severe infection of the lungs) had occurred among local residents. Most cases had occurred within a 3-week interval in mid- to late October; six persons had died. All cases had occurred in adults. Information doctors had obtained from several patients suggested that the cause of the illness may have been legionellosis, a disease caused by infection with the bacterium Legionella pneumophila.
You are the EIS Officer (CDC disease detective) assigned to the Louisiana health department who received a telephone call from the concerned physicians.
Serologic testing is the analysis of samples of blood serum for the presence of antibodies to specific disease agents, including bacteria and viruses. Some antibodies indicate recent infection and are called IgM class; antibodies indicating more distant past infection are called IgG. In Bogalusa, blood samples obtained from several patients during the earliest (acute) phase of illness had been negative for antibody to the Legionella bacterium (note, however, that for most infectious diseases antibodies cannot be detected during the first few weeks in the course of illness). No sputum (substances produced by the lining of the lungs and other parts of the respiratory tract) specimens had been collected for Legionnaires' testing, since the hospital's laboratory was not able to perform the tests.