Laidback Al
Well-known member
Time Interval Between Onset for WHO Confirmed Human Cases
For the last 22 days there have been no human confirmed H5N1 cases worldwide since Muhammad Nabi (Indonesia) who had onset of symptoms on October 31st, 2007. Twenty-two days between human cases is a long time, especially since the average number of days until the next confirmed case is usually only about 4 days. So, 22 days between onset for any chronologically sequential pair of worldwide H5N1 human cases is unusual but not a record.
There is some uncertainty of onset dates for WHO confirmed cases prior to 2005. About the middle of 2005, WHO record keeping and reporting started to be consistent to allow tabulation the time interval between onset for any two pair of confirmed cases. During the mid 2005, there were three long spans of 21, 24, and 26 days between onset for one case and the next reported and confirmed human case.
In August and September of 2006, there was a 26 day span between 2 cases in Indonesia. Two months later, there was another 30 days span between 2 more cases in Indonesia. And there was a 28 day interval between an Indonesian case in November 2006 and the next confirmed human case in China in December.
In the mid 2007 there was a 28 day span between a case in Indonesia in June and one reported in Egypt in July. Finally there was a 24 days span between 2 cases in Indonesia in late August and mid September.
Two observations about these data can be made. First, and somewhat confusing, is that the pattern from this November is repeating the pattern from fall of 2006. There seems to be a long interval between confirmed cases around this time for the past two years. Of course, this could be sampling error or random variation. But statistically H5N1 human cases start to increase between November and December (see chart), so it is surprising there is such a long interval between confirmed cases.
Second, and more important, is that the lack of any recent confirmed cases for the past 20+ days does not mean that the virus has subsided or is less dangerous. News reports need immediacy, and the lack of human cases or deaths pushes news and information about a potential pandemic to the back pages. Because no new human cases have been reported or confirmed lately does not mean that we should be letting our guard down.
For the last 22 days there have been no human confirmed H5N1 cases worldwide since Muhammad Nabi (Indonesia) who had onset of symptoms on October 31st, 2007. Twenty-two days between human cases is a long time, especially since the average number of days until the next confirmed case is usually only about 4 days. So, 22 days between onset for any chronologically sequential pair of worldwide H5N1 human cases is unusual but not a record.
There is some uncertainty of onset dates for WHO confirmed cases prior to 2005. About the middle of 2005, WHO record keeping and reporting started to be consistent to allow tabulation the time interval between onset for any two pair of confirmed cases. During the mid 2005, there were three long spans of 21, 24, and 26 days between onset for one case and the next reported and confirmed human case.
In August and September of 2006, there was a 26 day span between 2 cases in Indonesia. Two months later, there was another 30 days span between 2 more cases in Indonesia. And there was a 28 day interval between an Indonesian case in November 2006 and the next confirmed human case in China in December.
In the mid 2007 there was a 28 day span between a case in Indonesia in June and one reported in Egypt in July. Finally there was a 24 days span between 2 cases in Indonesia in late August and mid September.
Two observations about these data can be made. First, and somewhat confusing, is that the pattern from this November is repeating the pattern from fall of 2006. There seems to be a long interval between confirmed cases around this time for the past two years. Of course, this could be sampling error or random variation. But statistically H5N1 human cases start to increase between November and December (see chart), so it is surprising there is such a long interval between confirmed cases.
Second, and more important, is that the lack of any recent confirmed cases for the past 20+ days does not mean that the virus has subsided or is less dangerous. News reports need immediacy, and the lack of human cases or deaths pushes news and information about a potential pandemic to the back pages. Because no new human cases have been reported or confirmed lately does not mean that we should be letting our guard down.