Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 16, Number 4—April 2010

Household Transmission of Pandemic (H1N1) 2009, San Antonio, Texas, USA, April–May 2009

Oliver W. MorganComments to Author , Sharyn Parks, Trudi Shim, Patricia A. Blevins, Pauline M. Lucas, Roger Sanchez, Nancy Walea, Fleetwood Loustalot, Mark R. Duffy, Matthew J. Shim, Sandra Guerra, Fernando Guerra, Gwen Mills, Jennifer Verani, Bryan Alsip, Stephen Lindstrom, Bo Shu, Shannon L. Emery, Adam L. Cohen, Manoj Menon, Alicia M. Fry, Fatimah Dawood, Vincent P. Fonseca, and Sonja J. Olsen
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (O.W. Morgan, S. Parks, F. Loustalot, J. Verani, S. Lindstrom, B. Shu, S. Emery, A.L. Cohen, M. Menon, A.M. Fry, F. Dawood, S.J. Olsen); Department of State Health Services, Austin, Texas, USA (S. Parks, T. Shim, N. Walea, S. Guerra, V.P. Fonseca); United States Air Force School of Aerospace Medicine, Brooks City-Base, Texas, USA (P.M. Lucas, M.R. Duffy, M.J. Shim); San Antonio Metropolitan Health District, San Antonio, Texas, USA (P.A. Blevins, R. Sanchez, F. Guerra, B. Alsip); Comal County Health Department, New Braunfels, Texas, USA (G. Mills)

Main Article

Table 1

Index and secondary household case-patients with ARI, ILI, or laboratory-confirmed pandemic (H1N1) 2009, Region 8, Texas, April–May, 2009*

Household Index case-patients
Secondary case-patients
Serial interval, d†
Date of onset Age, y Case definition Date of onset Age, y Case definition
A Apr 18 14‡ A, no subtype Apr 25 21 Pandemic (H1N1) 2009 7
B Apr 19 5 Pandemic (H1N1) 2009 Apr 21 9 Pandemic (H1N1) 2009 2
C Apr 22 18 Pandemic (H1N1) 2009 Apr 25 <1 Pandemic (H1N1) 2009 3
D Apr 26 1 Pandemic (H1N1) 2009 May 4 27 Pandemic (H1N1) 2009 2
E Apr 26 16 Pandemic (H1N1) 2009 Apr 27 51 Pandemic (H1N1) 2009 1
Apr 27 8 ILI 1
F Apr 27 <1 Pandemic (H1N1) 2009 Apr 29 22 Pandemic (H1N1) 2009 2
May 6 47 ARI 9
G Apr 27 16 Pandemic (H1N1) 2009 May 1 16 Pandemic (H1N1) 2009 4
May 1 14 Pandemic (H1N1) 2009 4
H Apr 29 6 Pandemic (H1N1) 2009 Apr 3 <1 Pandemic (H1N1) 2009 1
I May 3 33 Pandemic (H1N1) 2009 May 7 15 Pandemic (H1N1) 2009 4

May 8
Pandemic (H1N1) 2009
Subtotal no. case-patients 9 13 3 (19)
J Apr 20 17 Pandemic (H1N1) 2009 Apr 26 14 ARI 6
K Apr 24 71 Pandemic (H1N1) 2009 Apr 27 65 ILI 3
L Apr 25 16 Pandemic (H1N1) 2009 Apr 27 16 ILI 2
M Apr 25 12 Pandemic (H1N1) 2009 Apr 28 30 ARI 3
Apr 28 33 ARI 3
Apr 30 6 ARI 5
N Apr 26 30 Pandemic (H1N1) 2009 May 1 28 ARI 5
O Apr 27 33 Pandemic (H1N1) 2009 May 5 53 ARI 8
P Apr 28 25 Pandemic (H1N1) 2009 May 4 14 ILI 6
Q Apr 29 1 Pandemic (H1N1) 2009 May 1 21 ILI 2
May 2 2 ILI 3
R Apr 29 8 Pandemic (H1N1) 2009 May 3 44 ARI 4
May 1
Pandemic (H1N1) 2009

May 3
Subtotal no. case-patients 10 13 3 (18)
T Apr 17 11 ILI Apr 21 18 Pandemic (H1N1) 2009 4
U Apr 18 48 ILI Apr 26 10 Pandemic (H1N1) 2009 8
V Apr 23 53 ILI Apr 26 42 Pandemic (H1N1) 2009 3
W Apr 24 5 ILI Apr 29 <1 Pandemic (H1N1) 2009 5
X Apr 28 26 ILI May 2 7 Pandemic (H1N1) 2009 4

May 3
Subtotal no. case-patients


4.5 (38)
Total no. case-patients 24 32 4 (19)

*ARI, acute respiratory infection; ILI, influenza-like illness (fever measured or subjective and cough or sore throat).
†Median (range) number of days between symptom onset of the index and secondary case-patients.
‡The influenza virus from this person could not be subtyped, possibly because of the quality of the sample or the length of time from symptom onset to sample collection. We considered this case-patient to have been infected with pandemic (H1N1) 2009.

Main Article

  1. World Health Organization. Influenza A (H1N1)—update 52. Laboratory-confirmed cases of new influenza A (H1N1) as officially reported to WHO by States Parties to the International Health Regulations (2005). [cited 2009 Jun 22].
  2. Centers for Disease Control and Prevention. Update: swine influenza A (H1N1) infections—California and Texas, April 2009. MMWR Morb Mortal Wkly Rep. 2009;58:4357.PubMedGoogle Scholar
  3. World Health Organization. Transcript of statement by Margaret Chan, Director-General of the World Health Organization. 11 June 2009 [cited 2009 Jul 7].
  4. Fox  JP, Cooney  MK, Hall  CE, Foy  HM. Influenza virus infections in Seattle families, 1975–1979. II. Pattern of infection in invaded households and relation of age and prior antibody to occurrence of infection and related illness. Am J Epidemiol. 1982;116:22842.PubMedGoogle Scholar
  5. Fox  JP, Hall  CE, Cooney  MK, Foy  HM. Influenzavirus infections in Seattle families, 1975–1979. I. Study design, methods and the occurrence of infections by time and age. Am J Epidemiol. 1982;116:21227.PubMedGoogle Scholar
  6. Foy  HM, Cooney  MK, Allan  I. Longitudinal studies of types A and B influenza among Seattle schoolchildren and families, 1968–74. J Infect Dis. 1976;134:3629.PubMedGoogle Scholar
  7. Taber  LH, Paredes  A, Glezen  WP, Couch  RB. Infection with influenza A/Victoria virus in Houston families, 1976. J Hyg (Lond). 1981;86:30313. DOIPubMedGoogle Scholar
  8. Texas Department of State Health Services. Health Service Region 8. 2009 [cited 2009 Jun 22].
  9. Centers for Disease Control and Prevention. Interim guidance on case definitions to be used for investigations of novel influenza A (H1N1) cases. 2009 [cited 2009 Jun 27].
  10. Carrat  F, Vergu  E, Ferguson  NM, Lemaitre  M, Cauchemez  S, Leach  S, Time lines of infection and disease in human influenza: a review of volunteer challenge studies. Am J Epidemiol. 2008;167:77585. DOIPubMedGoogle Scholar
  11. Lessler  J, Reich  NG, Brookmeyer  R, Perl  TM, Nelson  KE, Cummings  DA. Incubation periods of acute respiratory viral infections: a systematic review. Lancet Infect Dis. 2009;9:291300. DOIPubMedGoogle Scholar
  12. Centers for Disease Control and Prevention. CDC protocol of realtime RT-PCR for influenza A (H1N1) 2009 [cited 2009 Jun 23].
  13. Altman  DG. Practical statistics for medical research. London: Chapman and Hall/CRC Press; 1999.
  14. Novel Swine-Origin Influenza  A (H1N1) Virus Investigation Team, Dawood FS, Jain S, Finelli L, Shaw MW, Lindstrom S, Garten RJ, et al. Emergence of a novel swine-origin influenza A (H1N1) virus in humans. N Engl J Med. 2009;360:260515. DOIPubMedGoogle Scholar
  15. Centers for Disease Control and Prevention. Update: novel influenza A (H1N1) virus infection—Mexico, March–May, 2009. MMWR Morb Mortal Wkly Rep. 2009;58:5859.PubMedGoogle Scholar
  16. Health Protection Agency. Health Protection Scotland; National Public Health Service for Wales; HPA Northern Ireland Swine influenza investigation teams. Epidemiology of new influenza A (H1N1) virus infection, United Kingdom, April–June 2009. Euro Surveill. 2009;14. pii: 19232.
  17. Cowling  BJ, Fang  VJ, Riley  S, Malik Peiris  JS, Leung  GM. Estimation of the serial interval of influenza.. Epidemiology. 2009;20:3447. DOIPubMedGoogle Scholar
  18. Woodall  J, Rowson  KE, Mc  DJ. Age and Asian influenza, 1957. BMJ. 1958;2:13168. DOIPubMedGoogle Scholar
  19. Hayden  FG, Belshe  R, Villanueva  C, Lanno  R, Hughes  C, Small  I, Management of influenza in households: a prospective, randomized comparison of oseltamivir treatment with or without postexposure prophylaxis. J Infect Dis. 2004;189:4409. DOIPubMedGoogle Scholar
  20. Welliver  R, Monto  AS, Carewicz  O, Schatteman  E, Hassman  M, Hedrick  J, Effectiveness of oseltamivir in preventing influenza in household contacts: a randomized controlled trial. JAMA. 2001;285:74854. DOIPubMedGoogle Scholar
  21. Blumenfeld  HL, Kilbourne  ED, Louria  DB, Rogers  DE. Studies on influenza in the pandemic of 1957–1958. I. An epidemiologic, clinical and serologic investigation of an intrahospital epidemic, with a note on vaccination efficacy. J Clin Invest. 1959;38:199212. DOIPubMedGoogle Scholar
  22. Centers for Disease Control and Prevention. Serum cross-reactive antibody response to a novel influenza A (H1N1) virus after vaccination with seasonal influenza vaccine. MMWR Morb Mortal Wkly Rep. 2009;58:5214.PubMedGoogle Scholar
  23. Cate  TR, Kasel  JA, Couch  RB, Six  HR, Knight  V. Clinical trials of bivalent influenza A/New Jersey/76-A/Victoria/75 vaccines in the elderly. J Infect Dis. 1977;136(Suppl):S51825.PubMedGoogle Scholar
  24. Dolin  R, Wise  TG, Mazur  MH, Tuazon  CU, Ennis  FA. Immunogenicity and reactogenicity of influenza A/New Jersey/76 virus vaccines in normal adults. J Infect Dis. 1977;136(Suppl):S43542.PubMedGoogle Scholar
  25. Hayden  FG, Gubareva  LV, Monto  AS, Klein  TC, Elliot  MJ, Hammond  JM, Inhaled zanamivir for the prevention of influenza in families. Zanamivir Family Study Group. N Engl J Med. 2000;343:12829. DOIPubMedGoogle Scholar
  26. Monto  AS, Pichichero  ME, Blanckenberg  SJ, Ruuskanen  O, Cooper  C, Fleming  DM, Zanamivir prophylaxis: an effective strategy for the prevention of influenza types A and B within households. J Infect Dis. 2002;186:15828. DOIPubMedGoogle Scholar
  27. Centers for Disease Control and Prevention. Use of influenza A (H1N1) 2009 monovalent vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. National Center for Immunization and Respiratory Diseases. MMWR Recomm Rep. 2009;58(RR-10):18.

Main Article

Page created: December 28, 2010
Page updated: December 28, 2010
Page reviewed: December 28, 2010
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.