Communicability of rhinovirus type 16 or type 55 was studied in 24 childless couples; on partner (the donor) was infected with laboratory-grown virus. Initially, both partners lacked antibody to the challenge agent. Rates of transmission between partners were 41% and 33% for type 16 and type 55, respectively. These rates are similar to those determined in epidemiologic studies of natural rhinovirus infection. Although the mucosa of the anterior nares was shown to be highly susceptible to infection (less than one 50% tissue culture infective dose [TCID50]), transmission rarely occurred unless (1) at least 1,000 TCID50 of virus was recovered from the donor's nasal washing, (2) the donor had virus on his hands and anterior nares, (3) he was at least moderately symptomatic, and (4) he spent many hours with his spouse. Since person-to-person transfer of rhinovirus was so dependent upon time spent together and shedding of large amounts of virus by the donor, it seems possible that the chain of infection could be interrupted by environmental manipulation.

Transmission of infection with rhinovirus type 55 was attempted under natural circumstances of interaction among 26 experimentally infected donors and 33 antibody-free (titer, less than 1:3) recipients. In a total of three experiments, only two recipients (6%) became infected. In the first experiment no transmissions from five donors to nine recipients occurred after 2-3 hr of loud vocalization and card playing in a small room. In the second experiment a cold was transmitted to one (9%) of 11 recipients living in dormitory rooms for 36 hr in groups consisting chiefly of two donors and two recipients. In the third experiment one (8%) of 13 recipients was infected after kissing an infected donor. In studies with rhinovirus type 16, the 50% human infectious dose was found to be 0.28 TCID50 (50% tissue culture infectious dose) in the nose, 2,260 TCID50 on the tongue, and 11,000 TCID50 on the external nares. Rhinoviral infections are difficult to transmit by short-term natural exposure, perhaps because the agent must be present in overwhelming numbers to reach susceptible mucosal cells.

Nine naturally acquired rhinovirus infections in 31 asthmatic and nonasthmatic children were succeeded rapidly (2 to 26 days) by infections with heterologous rhinovirus.

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