Hantaan virus is a silent pathogen in rats and mice, but causes disease in humans (hemorrhagic fever with renal syndrome) after infection (Leduc et al., 1985) . Laboratory animal care workers working with infected animals as well as persons handling contaminated rat immunocytoma cell lines have been infected with this virus (Leduc et al., 1985; Lloyd and Jones, 1986; Mahy et al., 1991) . For this reason, all ATCC certified cell lines of rat origin have been screened for the presence of hantavirus. The following rat cell lines and rat hybridomas appeared free of hantavirus infection: CCL 38, 43, 45, 47, 82, 82.1, 97, 107, 144, 149, 165, 192, 216; CRL 1213 CRL , 1278 CRL , 1439 CRL , 1442 CRL , 1444 CRL , 1446 CRL , 1458 CRL , 1468 CRL , 1476 CRL , 1492 CRL , 1548 CRL , 1569 CRL , 1570 CRL , 1571 CRL , 1578 CRL , 1589 CRL , 1592 CRL , 1600 CRL , 1601 CRL , 1602 CRL , 1603 CRL , 1604 CRL , 1607 CRL , 1631 CRL , 1655 CRL , 1662 CRL , 1674 HB 58, 88, 90, 92, 100, 132; and TIB 104, 105, 106, 107, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 145, 146, 164, 166, 168, 175, 183, 184, 207, 210, 211, 213 (Leduc et al., 1985) . It should also be mentioned that cell lines of other species can also be contaminated by hantavirus. This virus had been detected in a human lung carcinoma cell line (A549) (French et al., 1981) and in Vero E6 cells (McCormick et al., 1982) .