Background: After a community investigation had implicated hospital admission as a shared feature of a cluster of acute Plasmodium falciparum malaria (AFM) cases in Riyadh, Saudi Arabia, we began an in-hospital investigation to determine the method of transmission.
Methods: We investigated all AFM patients admitted to one paediatric hospital for any reason from December, 1991, to April, 1992. We classified AFM as locally acquired (LAFM) if during the month before AFM onset the patient had not visited a malarious area, and as hospital acquired (HAFM) if the LAFM patient had been admitted to hospital during that month. We compared exposures of HAFM cases with those of other patients sampled from the same wards. We observed nursing practices and investigated by anonymous questionnaire how nurses administered parenteral drugs.
Findings: Of 21 LAFM cases, 20 (95%) had a previous hospital admission (exposure admission) compared with 15 (25%) of 61 other patients (p < 0.001; chi 2 test). During the exposure admission, all HAFM patients had occupied the same room as, or a room adjacent to, an AFM patient; 14 (23%) of 60 other patients occupied the same room or rooms adjacent to an AFM patient (p < 0.001, chi 2). 90% of HAFM patients received infusions through a heparin lock during the exposure admission, compared with 49% of 120 general patients (p < 0.001, chi 2). 10% of nurses admitted to using one syringe for more than one heparin lock and 50% filled syringes with enough heparin for three to ten heparin locks.
Interpretation: P falciparum was transmitted between patients when single syringes were used on heparin locks of sequential patients. This practice would easily transmit other blood-borne agents.