"The World Health Organisation says the number of confirmed...

"The World Health Organisation says the number of confirmed swine flu cases has risen by nearly 1,000 in 24 hours to 8,451."

"A mathematical study, published in the US journal Science this week, showed that the virus, while contagious, has a case fatality rate at 0.4-0.6 per cent - far lower than feared although somewhat higher than a normal "seasonal" flu."

http://www.abc.net.au/news/stories/2009/05/16/2572619.htm?section=justin

I just thought I would do a VERY SIMPLE analysis of the current trend in growth of infections. The latest trend in no of cases seems to be doubling every 6 days. (16/5 - 8,451 cases, 9/5 3,440 cases). However, the rate of doubling in reported cases seems to be falling from doubling every 2 days to every 6 days. This trend may continue.

I just thought I would show the data as most people seem to be implying WHO has overreacted.

Historical data:

Date....No of Cases....Days until No of Cases Doubled....Deaths....Days until No of Deaths Doubled...Reference

26/04/2009 38 2
27/04/2009 73 2 7 5 http://www.who.int/csr/don/2009_04_27/en/index.html
28/04/2009 105 2 7 4 http://www.who.int/csr/don/2009_04_28/en/index.html
29/04/2009 148 2 7 3 http://www.who.int/csr/don/2009_04_29/en/index.html
30/04/2009 257 2 8 2 http://www.who.int/csr/don/2009_04_30_a/en/index.html
1/05/2009 331 1 10 2 http://www.who.int/csr/don/2009_05_01/en/index.html
2/05/2009 658 3 17 5 http://www.who.int/csr/don/2009_05_02a/en/index.html
3/05/2009 898 3 20 4 http://www.who.int/csr/don/2009_05_03a/en/index.html
4/05/2009 1,085 3 25 8 http://www.who.int/csr/don/2009_05_04a/en/index.html
5/05/2009 1,490 3 29 9 http://www.who.int/csr/don/2009_05_05a/en/index.html
6/05/2009 1,893 4 29 8 http://www.who.int/csr/don/2009_05_06d/en/index.html
7/05/2009 2,371 4 42 http://www.who.int/csr/don/2009_05_07a/en/index.html
8/05/2009 2,500 4 44 http://www.who.int/csr/don/2009_05_08a/en/index.html
9/05/2009 3,440 6 45 http://www.who.int/csr/don/2009_05_09/en/index.html
10/05/2009 4,397 45 http://www.who.int/csr/don/2009_05_10/en/index.html
11/05/2009 4,694 48 http://www.who.int/csr/don/2009_05_11/en/index.html
12/05/2009 5,251 56 http://www.who.int/csr/don/2009_05_12/en/index.html
13/05/2009 5,728 56 http://www.who.int/csr/don/2009_05_13/en/index.html
14/05/2009 6,497 60 http://www.who.int/csr/don/2009_05_14/en/index.html
15/05/2009 7,520 60 http://www.who.int/csr/don/2009_05_15/en/index.html
16/05/2009 8,451 66 http://www.who.int/csr/don/2009_05_16/en/index.html


Projecting this forward with a doubling of cases and using the estimated death rate of 0.4% you get the following:

Date....No of Cases.......at 0.4 per cent

22/05/2009..........16,902.............68
28/05/2009..........33,804............135
3/06/2009...........67,608............270
9/06/2009..........135,216............541
15/06/2009.........270,432..........1,082
21/06/2009.........540,864..........2,163
27/06/2009.......1,081,728..........4,327
3/07/2009........2,163,456..........8,654
9/07/2009........4,326,912.........17,308
15/07/2009.......8,653,824.........34,615
21/07/2009......17,307,648.........69,231
27/07/2009......34,615,296........138,461
2/08/2009.......69,230,592........276,922
8/08/2009......138,461,184........553,845
14/08/2009.....276,922,368......1,107,689
20/08/2009.....553,844,736......2,215,379
26/08/2009...1,107,689,472......4,430,758
1/09/2009....2,215,378,944......8,861,516
7/09/2009....4,430,757,888.....17,723,032
13/09/2009...8,861,515,776.....35,446,063

Very simple analysis, makes no allowance for seasonal variation, chnage in detah rates from treatment, etc.
However, does highlight that if current infection trend continues, the size of the problem will not hit the actual statistics until August.

I actually expect it to be a lot less because of the end of the flu season in Northern Hemisphere and hopefully the development of a vacine by the next flu season.

Please don't critics too much. The exercise is really only a demonstration of what could happen if the current growth rate in infections were to continue and presumably why WHO is concerned.

Regards

SP