A constant flow of various pathogens enters the respiratory system on daily basis through the involuntary mechanism of breathing. Respiratory viral infections are common yet can be fatal in vulnerable populations. Respiratory syncytial virus (RSV) is one of the first and most common viruses that the human population acquire in the first two years of life. Despite the ability of most infants to recover from a RSV infection, many require hospitalization and, in few cases, die from such an infection. The pattern of seasonality of respiratory viruses also applies to RSV. In this work the temperature dependence of infectivity was studied in Hep-2 cells infected with RSV that had been incubated with bronchoalveolar lavage (BAL) fluid. The results indicate a temperature dependence of infectivity. Inhibition of the viral infectivity was observed at three different temperatures 37 ̊C, 40 ̊C and 42 ̊C. The inhibition appears to be linked to the appearance of large agglutinates that appear to reduce the infectivity of RSV. Such a study found that viral neutralization is dependent on a temperature-dependent agglutination reaction. The causality of agglutination formation requires further investigation in order to conclusively confirm the immunological component(s) of this reaction, and how temperature is contributing to this reaction.