Nat. Med. 8, 950–954 (2002); published online 26 August 2002; addendum published after print 5 October 2012

The above paper originally reported that H5N1 viruses are resistant to interferon in the SJPL cell line. The editors wish to alert our readers about three facts that may affect this conclusion. First, Ngunjiri et al. (Nat. Med. 18, 1456–1457, 2012) have recently found that aliquots of the SJPL cell line obtained from the American Type Culture Collection were heavily contaminated with mycoplasma. Although the mycoplasma status of the cells used in the original paper is unknown, it is not possible to rule out that they were contaminated. Second, SJPL cells were originally reported to be of porcine origin, but a recent analysis (Silversides, D.W. et al. J. Virol. 84, 5454–5455, 2010) has indicated that they are of simian origin. Third, Ngunjiri et al. have found H5N1 viruses to be sensitive to interferons in all cell lines tested from multiple species.