The logarithm of the number of cases is recorded as a pair with its date. A line is fitted to this data. The line's starting point and slope are adjusted to minimize the sum of the squares of differences between the line and the actual data. This is called a least squares linear fit.
The doubling time in days is the log base 10 of 2 (for doubling) divided by the slope of the line. The table below tells the equation for finding the number of cases on a given date. Also shown is the equation for finding the date at which a certain number of cases will be reached. The average error squared is the total error for the line divided by the number of data points. The average error per data point is the square root of that, and it is expressed as a percent of the number of cases.
Doubling times are computed using the data from the most recent 21 days.
| July 7, 2003 | Equation for the forecast of |
World Cases |
Cases on a future date
cases = exp (2.30258 * ((days after June 20, 2003) * 2.0e-5 + 3.92667)) |
World Cases |
Date of a given number of cases
(days after June 20, 2003) = (log10(cases) - 3.92667) / 2.0e-5 |
World Cases |
average error of exponential curve = 0.1% of cases at each data point |
World Deaths |
Deaths by a future date
deaths = exp (2.30258 * ((days after June 20, 2003) * 0.00058 + 2.90315)) |
World Deaths |
Date of a given number of deaths
(days after June 20, 2003) = (log10(deaths) - 2.90315) / 0.00058 |
World Deaths |
average error of exponential curve = 0.2% of deaths at each data point |
US cases |
Cases on a future date
cases = exp (2.30258 * ((days after June 20, 2003) * 0.00094 + 1.85901)) |
US cases |
Date of a given number of cases
(days after June 20, 2003) = (log10(cases) - 1.85901) / 0.00094 |
US cases |
average error of exponential curve = 1.0% of cases at each data point |
This data comes is from the WHO Cumulative Number of Reported Cases (SARS). US cases before April 20th were recalculated by mutiplying the original data by 0.1683 (which is 35/208).
Date, US cases, US deaths, World cases, World deaths
3/17 United States 0 0 Total 167 4
3/18 United States 0 0 Total 219 4
3/19 United States 2 0 Total 264 9
3/20 United States 2 0 Total 306 10
3/21 United States 2 0 Total 350 10
3/22 United States 4 0 Total 386 11
3/24 United States 6 0 Total 456 17
3/25 United States 7 0 Total 487 17
3/26 United States 7 0 Total 1323 49
3/27 United States 8 0 Total 1408 53
3/28 United States 9 0 Total 1485 53
3/29 United States 10 0 Total 1550 54
3/31 United States 10 0 Total 1622 58
4/1 United States 12 0 Total 1804 62
4/2 United States 12 0 Total 2223 78
4/3 United States 14 0 Total 2270 79
4/4 United States 17 0 Total 2353 84
4/5 United States 19 0 Total 2416 89
4/7 United States 24 0 Total 2601 98
4/8 United States 25 0 Total 2671 103
4/9 United States 25 0 Total 2722 106
4/10 United States 26 0 Total 2781 111
4/11 United States 28 0 Total 2890 116
4/12 United States 28 0 Total 2960 119
4/14 United States 29 0 Total 3169 144
4/15 United States 32 0 Total 3235 154
4/16 United States 32 0 Total 3293 159
4/17 United States 33 0 Total 3389 165
4/18 United States 35 0 Total 3461 170
4/19 United States 37 0 Total 3547 182
4/21 United States 39 0 Total 3861 217
4/22 United States 38 0 Total 3947 229
4/23 United States 39 0 Total 4288 251
4/24 United States 37 0 Total 4439 263
4/25 United States 39 0 Total 4649 274
4/26 United States 41 0 Total 4836 293
4/28 United States 41 0 Total 5050 321
4/29 United States 41 0 Total 5462 353
4/30 United States 52 0 Total 5663 372
5/1 United States 54 0 Total 5865 391
5/2 United States 56 0 Total 6054 417
5/3 United States 54 0 Total 6234 435
5/5 United States 61 0 Total 6583 461
5/6 United States 65 0 Total 6727 478
5/7 United States 65 0 Total 6903 495
5/8 United States 63 0 Total 7053 506
5/9 United States 63 0 Total 7183 514
5/10 United States 64 0 Total 7296 526
5/12 United States 64 0 Total 7447 552
5/13 United States 64 0 Total 7548 573
5/14 United States 64 0 Total 7628 587
5/15 United States 64 0 Total 7699 598
5/16 United States 65 0 Total 7739 611
5/17 United States 66 0 Total 7761 623
5/19 United States 67 0 Total 7864 643
5/20 United States 67 0 Total 7919 662
5/21 United States 66 0 Total 7956 666
5/22 United States 65 0 Total 8046 682
5/23 United States 65 0 Total 8117 689
5/24 United States 65 0 Total 8141 696
5/26 United States 65 0 Total 8202 725
5/27 United States 65 0 Total 8221 735
5/28 United States 66 0 Total 8240 745
5/29 United States 66 0 Total 8295 750
5/30 United States 66 0 Total 8317 754
5/31 United States 66 0 Total 8360 764
6/2 United States 66 0 Total 8384 770
6/3 United States 68 0 Total 8398 772
6/4 United States 69 0 Total 8402 772
6/5 United States 69 0 Total 8403 775
6/6 United States 68 0 Total 8404 779
6/9 United States 68 0 Total 8421 784
6/10 United States 69 0 Total 8430 789
6/11 United States 71 0 Total 8435 789
6/12 United States 70 0 Total 8445 790
6/13 United States 71 0 Total 8454 792
6/16 United States 72 0 Total 8460 799
6/17 United States 73 0 Total 8464 799
6/18 United States 75 0 Total 8465 801
6/19 United States 75 0 Total 8462 804
6/20 United States 74 0 Total 8461 804
6/23 United States 74 0 Total 8459 805
6/24 United States 75 0 Total 8458 807
6/25 United States 75 0 Total 8460 808
6/26 United States 74 0 Total 8456 809
6/27 United States 74 0 Total 8450 810
6/30 United States 73 0 Total 8447 811
7/1 United States 73 0 Total 8445 812
7/2 United States 73 0 Total 8442 812
7/3 United States 73 0 Total 8439 812
7/4 United States 73 0 Total 8439 812
7/7 United States 73 0 Total 8439 812
The WHO does not report statistics on Sundays, so this page does not change on Sundays.
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(c) Ted Kaehler 2003. Permission is hereby granted for unlimited reproduction and redistribution of this page and its information.