ArticlesFactors associated with case fatality of human H5N1 virus infections in Indonesia: a case series
Introduction
As of Feb 12, 2008, highly pathogenic avian influenza A (H5N1) had affected 360 human beings since October, 2003,1 and there is concern that these infections could be the prelude to a global pandemic if sustained human-to-human transmission develops. The high case-fatality rate of 62·8%1 would be devastating if maintained in a pandemic. Indonesia has had the most patients with H5N1 influenza and one of the highest case-fatality rates worldwide. The first confirmed human H5N1 infection in Indonesia was in June, 2005,2 and since then the number of patients has increased steadily, and case fatality increased year-on-year from 2005 to 2007. Although there have been many hypotheses about the reasons behind the high case-fatality rates of H5N1 influenza infection, there is little evidence pointing to specific causes.
Indonesia has built surveillance and referral systems for human H5N1 infections since February, 2004. Health officers at the central, provincial, and district levels have been trained on surveillance and case identification and reporting according to WHO case definitions.3 Health officers are constantly on the lookout for cases that meet the definition of a suspect case for preliminary investigation and to obtain samples for confirmatory testing. Where clinically possible, suspected human cases are treated with oseltamivir, which is available at government hospitals and primary health-care centres throughout the country. Suspect cases are also immediately sent to one of 44 avian influenza referral hospitals (currently being increased to 100) that are equipped with isolation and intensive-care facilities, as well as case-management guidelines and expertise. In the areas where H5N1 cases have occurred, referral hospitals are all within 1 day's travel by land.
We describe the factors obtained from case investigations that are associated with case-fatality of human H5N1 infection in Indonesia.
Section snippets
Patients and data
127 people infected with H5N1 were confirmed with onset from June 22, 2005, to Feb 1, 2008. The 127 patients included the first 54 in Indonesia mentioned in a previous paper,4 although this study uses a new dataset from the case-investigation reports.
All patients with suspected H5N1 had specimens (throat and nasal swabs) taken and sent to national laboratories for testing by RT-PCR and sequencing,4 with results available within a few days. For cases before 2007, specimens were sent to WHO
Results
The case-fatality rate from 2005 to 2008 increased from 65·0% in 2005 (13 of 20 cases), to 81·8% in 2006 (45 of 55 cases), to 86·8% in 2007 (37 of 42 cases), and 80·0% up to Feb 2, 2008 (eight of ten cases). The yearly trend was significant (p=0·05) from 2005 to 2007.
From the exposure history, 54 patients had direct exposure, 50 had indirect exposure, and 23 had inconclusive exposure. There were 63 infections in men and boys. Median age of patients was 20 years (range 2–67). 58 patients lived
Discussion
H5N1 case fatality rates in Indonesia have increased from 2005 to 2007, even though case management protocols, surveillance, and equipment across the country have improved since 2005. Not being part of a cluster, residence in an urban area, and indirect exposure were positively associated with mortality. From the multivariate analysis, only patients that were part of clusters had significantly lower case fatality than did those who were not part of clusters. Secondary cases in clusters were
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