Family clustering of avian influenza A (HSN1).To the Editor: The unprecedented epizootic ep·i·zo·ot·ic adj. Affecting a large number of animals at the same time within a particular region or geographic area. Used of a disease. ep of avian influenza avian influenza: see influenza. A (H5N1) in Asia poses a serious threat of causing the next global influenza pandemic
1. to invade and produce infection in. 2. to transmit a pathogen or disease to. in·fect v. 1. humans and cause severe illness and death (1-4). Fortunately, these viruses have not yet demonstrated the capacity for efficient and sustained person-to-person transmission, although limited person-to-person transmission was the cause of at least 1 family cluster family cluster Epidemiology A grouping of disorders found in ≥ 2 members of a family of cases (5). Since family clusters of H5N1 illness may be the first suggestion of a viral or epidemiologic ep·i·de·mi·ol·o·gy n. The branch of medicine that deals with the study of the causes, distribution, and control of disease in populations. [Medieval Latin epid change, we have been monitoring them with great interest. Through our regional contacts and public sources, we have monitored family clusters and other aspects of H5N1 in Southeast Asia Southeast Asia, region of Asia (1990 est. pop. 442,500,000), c.1,740,000 sq mi (4,506,600 sq km), bounded roughly by the Indian subcontinent on the west, China on the north, and the Pacific Ocean on the east. . A cluster was defined as [greater than or equal to] 2 family members with laboratory-confirmed H5N1 or [greater than or equal to] 2 family members with severe pneumonia pneumonia (n  mōn`yə), acute infection of one or both lungs that can be caused by a bacterium, usually Streptococcus pneumoniae or respiratory death, at least one of which had
confirmed H5N1. To determine if family cluster events had increased over
time, we divided the number of cluster events by the total number of
days in 2 discrete periods and calculated rate ratios (RR) and 95%
confidence intervals confidence interval,n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. (CI). To determine whether the increase in family clustering was attributable to an increase in the number of cases, we divided the number of family units with [greater than or equal to] 2 laboratory-confirmed cases by the total number of family units in the period. Percentage of deaths was also compared. From January 2004 to July 2005, 109 cases of avian influenza A (H5N1) were officially reported to the World Health Organization (WHO) (6). During this time, 15 family clusters were identified (Table). Of the 11 (73%) clusters that occurred in Vietnam, 7 were in northern Vietnam. Cluster size ranged from 2 to 5 persons, and 9 (60%) had [greater than or equal to] 2 persons with laboratory-confirmed H5N1. Cluster 6 in Thailand was well documented and was likely the result of limited person-to-person transmission (5). For the other clusters, epidemiologic information was insufficient to determine whether person-to-person transmission occurred. In at least 3 clusters in Vietnam (Table; clusters 5, 7, and 11), >7 days occurred between the onset of the first and the next case, suggesting that simultaneous acquisition from a common source was unlikely. In cluster 11, 2 nurses assisted in the care of the index case-patient and subsequently were hospitalized with severe pneumonia; 1 had laboratory-confirmed H5N1. Family clusters were slightly more likely to have occurred between December 2004 and July 2005 than in the first year of the outbreak (9 clusters in 243 days or 3.7 per 100 days vs. 6 clusters in 365 days or 1.6 per 100 days, respectively; RR 2.3, 95% CI 0.8-6.3). The difference was similar when the periods were limited to the same 8 months, 1 year apart (RR 1.8, 95% CI 0.6-5.4). Twenty-five (61%) of the 41 patients in the 15 family clusters died; the 7 persons who recovered or were not ill experienced secondary cases. Family clusters are still occurring; however, they do not appear to be increasing as a proportion of total cases. The proportion of families that were part of a cluster was similar from December 2004 to July 2005 to the proportion in the first year (6/55, 11% vs. 3/41, 7%, respectively, p = 0.7). However, the proportion of deaths dropped significantly, from 32 of 44 (73%) during December 2003 to November 2004, to 23 of 65 (35%) during December 2004 to July 2005 (p<0.0001). Although reports of H5N1 family clusters slightly increased, the increase was not statistically significant. Nevertheless, we believe any cluster of cases is of great concern and should be promptly and thoroughly investigated because it might be the first indication of viral mutations resulting in more efficient person-to-person spread. Family clustering does not necessarily indicate person-to-person transmission, as it may also result from common household exposures to the same H5N1-infected poultry poultry, domesticated fowl kept primarily for meat and eggs; including birds of the order Galliformes, e.g., the chicken, turkey, guinea fowl, pheasant, quail, and peacock; and natatorial (swimming) birds, e.g., the duck and goose. or from other exposures, such as to uncooked poultry products. The decrease in proportion of deaths during 2005 is another epidemiologic change that should be monitored closely because it may reflect viral adaptation to the human host. Surveillance for human cases of avian influenza has been intensified in·ten·si·fy v. in·ten·si·fied, in·ten·si·fy·ing, in·ten·si·fies v.tr. 1. To make intense or more intense: in recent months, perhaps resulting in the identification of less severe cases. Alternatively, more widespread laboratory testing may be associated with false-positive results. No evidence to date shows genetic reassortment between H5N1 and human influenza A influenza A n. Influenza caused by infection with a strain of influenza virus type A. influenza A Infectious disease An avian virus, especially of ducks–which in China live near the pig reservoir and 'vector'; viruses (7). Viruses isolated from case-patients need to be immediately sequenced and characterized in relation to previously circulating cir·cu·late v. cir·cu·lat·ed, cir·cu·lat·ing, cir·cu·lates v.intr. 1. To move in or flow through a circle or circuit: blood circulating through the body. 2. viruses to see whether they are evolving. Recent modeling studies suggest that containing a pandemic pandemic /pan·dem·ic/ (pan-dem´ik) 1. a widespread epidemic of a disease. 2. widely epidemic. pan·dem·ic adj. Epidemic over a wide geographic area. n. at its source may be possible because emergent emergent /emer·gent/ (e-mer´jent) 1. coming out from a cavity or other part. 2. pertaining to an emergency. emergent 1. coming out from a cavity or other part. 2. coming on suddenly. pandemic viruses may be less transmissible transmissible /trans·mis·si·ble/ (trans-mis´i-b'l) capable of being transmitted. trans·mis·si·ble adj. Capable of being conveyed from one person to another. than commonly assumed (8), and antiviral antiviral /an·ti·vi·ral/ (-vi´ral) destroying viruses or suppressing their replication, or an agent that so acts. an·ti·vi·ral adj. treatment and chemoprophylaxis chemoprophylaxis /che·mo·pro·phy·lax·is/ (-pro?fi-lak´sis) prevention of disease by means of a chemotherapeutic agent. che·mo·pro·phy·lax·is n. Disease prevention by use of chemicals or drugs. may slow the spread (9). Although the logistics of an attempt to contain the beginning of a potential influenza pandemic are formidable, we believe it is not beyond the capability of the modern global public health system. As WHO (10) has called for, countries should intensify in·ten·si·fy v. in·ten·si·fied, in·ten·si·fy·ing, in·ten·si·fies v.tr. 1. To make intense or more intense: their pandemic preparedness pre·par·ed·ness n. The state of being prepared, especially military readiness for combat. Noun 1. preparedness - the state of having been made ready or prepared for use or action (especially military action); "putting them plans and strengthen international collaborations. Sonja J. Olsen, * Kumnuan Ungchusak, ([dagger]) Ly Sovann, ([double dagger double dagger n. A reference mark (  ) used in printing and writing. Also called diesis.Noun 1. ]) Timothy M. Uyeki, ([section]) Scott F. Dowell, * Nancy J. Cox, ([section]) William Aldis, ([paragraph]) and Supamit Chunsuttiwat ([dagger]) * International Emerging Infections Program, Nonthaburi, Thailand; ([dagger]) Ministry of Public Health, Nonthaburi, Thailand; ([double dagger]) Ministry of Health, Phnom Penh Phnom Penh (nŏm pĕn, pənŏm`) or Phnum Penh (pən m`), city (1994 est. pop. , Cambodia; ([dagger]) Centers
for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. , Atlanta, Georgia, USA; and
([paragraph]) World Health Organization, Nonthaburi, ThailandReferences (1.) Hien TT, de Jong De Jong is the most common Dutch surname. Many people bear this name, including many important historical figures. Some of these people are mentioned below. De Jong may mean:
a·vi·an adj. Of, relating to, or characteristic of birds. influenza--a challenge to global health care structures. N Engl J Med. 2004;351: 2363-5. (2.) Centers for Disease Control and Prevention. Cases of influenza A (H5N1--Thailand, 2004. MMWR MMWR Morbidity & Mortality Weekly Report Epidemiology A news bulletin published by the CDC, which provides epidemiologic data–eg, statistics on the incidence of AIDS, rabies, rubella, STDs and other communicable diseases, causes of mortality–eg, Morb Mortal mortal /mor·tal/ (mor´t'l) 1. subject to death, or destined to die. 2. fatal. mor·tal adj. 1. Liable or subject to death. 2. Wkly Rep. 2004;53:100-3. (3.) Chokephaibulkit K, Uiprasertkul M, Puthavathana P, Chearskul P, Auewarakul P, Dowell SF, et al. A child with avian influenza A (H5N1) infection. Pediatr Infect Dis J. 2005 ;24:162-6. (4.) Chotpitayasunondh T, Ungchusak K, Hanshaoworakul W, Chunsuthiwat S, Sawanpanyalert P, Kijphati R, et al. Human disease from influenza A (H5N 1), Thailand, 2004. Emerg Infect Dis. 2005; 11:201-9. (5.) Ungchusak K, Auewarakul P, Dowell SF, Kitphati R, Auwanit W, Puthavathana P, et al. Probable person-to-person transmission of avian influenza A (H5N1). N Engl J Med. 2005;352:333-40. (6.) World Health Organization. Cumulative number of confirmed human cases of avian influenza A/(H5N 1) reported to WHO. Vol. 2005. Geneva Geneva, canton and city, Switzerland Geneva (jənē`və), Fr. Genève, canton (1990 pop. 373,019), 109 sq mi (282 sq km), SW Switzerland, surrounding the southwest tip of the Lake of Geneva. : The Organization; 2005. [cited 2005 Sep 22]. Available from http://www.who.int/csr/disease/avian_influ enza/country/cases_table_2005 07 27/en/i ndex.html (7.) World Health Organization. Evolution of H5N1 avian influenza viruses in Asia. Emerg Infect Dis. 2005;11:1515-21. (8.) Mills CE, Robins JM, Lipsitch M. Transmissibility trans·mis·si·ble adj. That can be transmitted: transmissible signals. trans·mis of 1918 pandemic influenza influenza or flu, acute, highly contagious disease caused by a virus; formerly known as the grippe. There are three types of the virus, designated A, B, and C, but only types A and B cause more serious contagious infections. . Nature. 2004;432:904-6. (9.) Longini IM Jr, Nizam A, Xu S, Ungchusak K, Hanshaoworakul W, Cummings DA, et al. Containing pandemic influenza at the source. Science. 2005 Aug 12;309:1083-7. Epub 2005 Aug 3. (10.) World Health Organization. Influenza pandemic preparedness and response. Geneva: The Organization; 2005. [cited 2005 Sep 22]. Available from http://www.who.int/gb/ ebwha/pdf_files/EB 115/B 115_44-en.pdf Address for correspondence: Sonja J. Olsen, CDC See Control Data, century date change and Back Orifice. CDC - Control Data Corporation , Box 68, American Embassy, APO apo- 1 A prefix indicating a protein component in a conjugated molecule–eg, apoferritin, apolipoprotein, see there 2 Apolipoprotein, see there AP 96546; fax: 66-2-580-0911; email: SOlsen@ cdc.gov
Table. Family clusters of influenza A (H5N1) in Southeast Asia,
January 2004-July 2005 *
Cluster Onset of index case Country Age (y)/Sex
1 Dec 03 Vietnam (N) 12/F
30/F
2 Dec 03 Vietnam (N) 5/M
7/F
3 Jan 04 Vietnam (N) 31/M
30/F
28/F
23/F
4 Jan 04 Thailand 6/M
33/F
5 Jul 04 Vietnam (S) 19/M
22/F
25/F
6 Sep 04 Thailand 11/F
26/F
32/F
7 Dec 04 Vietnam (N) 46/M
42/M
36/M
8 Jan 05 Vietnam (S) 17/M
22/F
9 Jan 05 Vietnam (S) 35/F
13/F
10 Jan 05 Cambodia 14/M
25/F
11 Feb 05 Vietnam (N) 21/M
14/F
80/M
12 Feb 05 Vietnam (N) 69/M
61/F
13 Mar 05 Vietnam 13/F
5/M
Adult/F
14 Mar 05 Vietnam (N) 39/M
Adult/F
4 mo/NN
3/NN
10/NN
15 Jul 05 Indonesia 8/F
1/F
38/M
Relation to
Cluster index case H5N1 Onset
1 Self + Dec 25
Mother + Jan 1
2 Self + Dec 29 ([dagger])
Sister NT NN
3 Self NT Jan 7 ([dagger])
Sister + Jan 10
Wife + Jan 10
Sister + Jan 11
4 Self + Jan 8
Mother NT Jan 8
5 Self NT Jul 23
Cousin NT NN
Sister + Jul 31
6 Self NT Sep 2
Mother + Sep 11
Aunt + Sep 16
7 Self + Dec 26
Brother + Jan 10 ([dagger])
Brother + Not ill
8 Self + Jan 10 ([dagger])
Sister NN NN
9 Self + Jan 14
Daughter + Jan 20
10 Self NT NN
Sister + Jan 21
11 Self + Feb 14
Sister + Feb 23
Grandfather + Not ill
12 Self + Feb 19
Wife + Not ill
13 Self NT Mar 9 ([section])
Brother + Mar 12 ([dagger])
Aunt P NN
14 Self + Mar 22 ([dagger])
Wife + Mar 22 ([dagger])
Child + Mar 22 ([dagger])
Child + Mar 22 ([dagger])
Child + Mar 22 ([dagger])
15 Self + ([paragraph]) Jun 24
Sister NT Jun 29
Father + Jul 12
Cluster Outcome
1 D
D
2 D
D
3 D
D
R
D
4 D
D
5 D
D
D
6 D
D
R
7 D
R
Not ill
8 D
Unknown ([double dagger])
9 D
D
10 D
D
11 Unknown ([double dagger])
Unknown ([double dagger])
Not ill
12 D
Not ill
13 D
R
Unknown ([double dagger])
14 Unknown ([double dagger])
Unknown ([double dagger])
Unknown ([double dagger])
Unknown ([double dagger])
Unknown ([double dagger])
15 D
D
D
* D, respiratory death; N, north; NT, not tested; NN, not noted; P,
pending; R, recovered; S, south.
([dagger]) Date of hospitalization.
([double dagger]) Had respiratory symptoms, was hospitalized (unknown
for #13), and outcome was unknown.
([section]) Date of death.
([paragraph]) Serologically confirmed; classified as a probable case by
the World Health Organization.
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