sharon sanders
Editor-in-Chief & President
hat tip to Theresa42
Little Evidence for Genetic Susceptibility to Influenza A (H5N1) from Family Clustering Data
Virginia E. Pitzer,* Sonja J. Olsen,† Carl T. Bergstrom,‡ Scott F. Dowell,† and Marc Lipsitch*
*Harvard School of Public Health, Boston, Massachusetts, USA; †Centers for Disease Control and Prevention,
Atlanta, Georgia, USA; and ‡University of Washington, Seattle, Washington, USA
Since December, 2003, 36 family clusters among 261 confirmed human cases of
influenza A (H5N1) have been documented (1,2). These clusters range in size from 2 to 8
infected persons; in only 4 clusters were 2 unrelated family members (e.g., husband and wife)
infected. This pattern has been considered by the World Health Organization as evidence of
genetic variation in susceptibility (3–5), but we show this observation provides little grounds
for this inference. We describe a null model in which nuclear families experience a common
exposure to an avian influenza virus. The observed degree of clustering in blood relatives is
consistent with that expected by chance alone in the absence of genetic variation in
susceptibility; other features of the data are also consistent with the null model.
Little Evidence for Genetic Susceptibility to Influenza A (H5N1) from Family Clustering Data
Virginia E. Pitzer,* Sonja J. Olsen,† Carl T. Bergstrom,‡ Scott F. Dowell,† and Marc Lipsitch*
*Harvard School of Public Health, Boston, Massachusetts, USA; †Centers for Disease Control and Prevention,
Atlanta, Georgia, USA; and ‡University of Washington, Seattle, Washington, USA
Since December, 2003, 36 family clusters among 261 confirmed human cases of
influenza A (H5N1) have been documented (1,2). These clusters range in size from 2 to 8
infected persons; in only 4 clusters were 2 unrelated family members (e.g., husband and wife)
infected. This pattern has been considered by the World Health Organization as evidence of
genetic variation in susceptibility (3–5), but we show this observation provides little grounds
for this inference. We describe a null model in which nuclear families experience a common
exposure to an avian influenza virus. The observed degree of clustering in blood relatives is
consistent with that expected by chance alone in the absence of genetic variation in
susceptibility; other features of the data are also consistent with the null model.