TNF and susceptibility to pneumonia measurement: HMPV pneumonia group had lower IL-2 (median levels, pg/ml: 3.40 vs. 5.80, p < 0.001), higher IL-4 (median levels, pg/ml: 3.00 vs. 1.40, p < 0.001), IL-6 (median levels, pg/ml: 8.10 vs. 4.10, p = 0.001), IL-10 (median levels, pg/ml: 9.20 vs. 2.40, p < 0.001) and IFN-γ (median levels, pg/ml: 8.70 vs. 4.60, p < 0.001), whereas no significant difference of TNF-α levels was found between the two groups (median levels, pg/ml, 2.40 vs. 2.30, p = 0.160).