CONCLUSION

A better understanding of transmission dynamics is essential in influenza pandemic planning. If a substantial proportion of transmission were to occur during the presymptomatic phase or from asymptomatic individuals, then infection control measures such as contact tracing and quarantine of exposures will be of limited value, in addition to constraints based on the short serial interval for influenza transmission. However, we have found limited evidence to suggest the importance of such transmission. The role of asymptomatic or presymptomatic influenza-infected individuals in disease transmission may have been overestimated in recent articles dealing with pandemic planning. More definitive influenza transmission studies are needed.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2646474/