2.7.1 Number of patients expected
Estimate the number of cases that can be expected in the outbreak to determine the resources needed for case management.
The calculation requires applying a representative attack rate (AR) to the total population of the atrisk community. An appropriate AR can be obtained from previous outbreaks in the area.
If historical data are not available or are deemed to be incomplete or unreliable, an AR typical for the given context can be chosen (Section 1.1.7).
Keep in mind that an AR derived from historical data or selected as typical for the specific context is only an approximation.
An outbreak can be expected to be severe if it occurs earlier in the season than usual or if a large number of people or locations are affected during the first weeks.
For an example of calculation of the number of expected cases, see Box 2.1.
2.7.2 Peak bed capacity
Sufficient bed capacity is essential, particularly at the peak of the epidemic. Estimating peak bed capacity while still in the early phase of an outbreak gives planners and logistic services an idea of the size and number of cholera facilities that will be required.
The calculation of peak bed capacity is based on the total number of patients expected and the following assumptions derived from previous experience:
– 2530% of patients will have severe dehydration, 3040% some dehydration, and 3040% no dehydration.
– All patients with severe dehydration and approximately half of patients with some dehydration will need a bed for at least a night.
Based on these two first assumptions, approximately 50% of all cholera patients seeking medical care will need a bed.
– The combined average length of stay for patients hospitalized with some and severe dehydration is 2 days (length of stay can be shorter in settings with easy access to care and longer in settings with difficult access or more complicated patients such as the elderly or pregnant women).
– Approximately 1520% of patients will seek medical care during the peak week (less for rural settings, more for crowded urban settings).
These estimated values can be adjusted to fit the local context if sufficiently reliable detailed data from prior outbreaks are available.
For an example of calculation of peak bed capacity required, see Box 2.1.
Box 2.1  Number of expected cases and peak bed capacity required
Examples of calculations according to the context Refugee camp
Urban area
Rural area 
2.7.3 Treatment supplies
Items for curative care
The initial estimation of needs is based on the number of expected cases, taking into account known available existing stock, if any.
The calculations presented in the Table 2.1 are based on the following standards: 10 litres of ORS per patient, 810 litres of RL per patient with severe dehydration, 1 infusion set for 2 litres of RL, 1 catheter for 3 litres of RL, an antibiotic therapy for patients with some (= moderate) and severe dehydration, zinc sulfate for all children under 5 years.
Table 2.1  Examples of calculations for determining medication supply needs
Refugee camp 
Estimated 
Number of cases 
Essential items for rehydration 
Attack rate 
5% 
30 000 x 0.05 = 1500 
─ 
No dehydration 
40% 
1500 x 0.40 = 600 
10 l ORS x 600 cases = 6000 sachets ORS 
Some dehydration 
35% 
1500 x 0.35 = 525 
10 l ORS x 525 cases = 5250 sachets ORS 
Severe dehydration 
25% 
1500 x 0.25 = 375 
10 l ORS x 375 cases = 3750 sachets ORS 
Complementary treatments  
Doxycycline 
60% 
1500 x 0.60 = 900 
3 tab x 900 cases = 2700 tab 
Zinc sulfate 
20% 
1500 x 0.20 = 300 
10 tab x 300 cases = 3000 tab 
Urban area 
Estimated 
Number of cases 
Essential items for rehydration 
Attack rate 
2% 
600 000 x 0.02 = 12 000 
─ 
No dehydration 
40% 
12 000 x 0.40 = 4800 
10 l ORS x 4800 cases = 48 000 sachets ORS 
Some dehydration 
35% 
12 000 x 0.35 = 4200 
10 l ORS x 4200 cases = 42 000 sachets ORS 
Severe dehydration 
25% 
12 000 x 0.25 = 3000 
10 l ORS x 3000 cases = 30 000 sachets ORS 
Complementary treatments  
Doxycycline 
60% 
12 000 x 0.60 = 7200 
3 tab x 7200 cases = 22 000 tab 
Zinc sulfate 
20% 
12 000 x 0.20 = 2400 
10 tab x 2400 cases = 24 000 tab 
Rural area 
Estimated 
Number of cases 
Essential items for rehydration 
Attack rate 
1% 
200 000 x 0.01 = 2000 
─ 
No dehydration 
30% 
2000 x 0.30 = 600 
10 l ORS x 600 cases = 6000 sachets ORS 
Some dehydration 
40% 
2000 x 0.40 = 800 
10 l ORS x 800 cases = 8000 sachets ORS 
Severe dehydration 
30% 
2000 x 0.30 = 600 
10 l ORS x 600 cases = 6000 sachets ORS 
Complementary treatments  
Doxycycline 
70% 
2000 x 0.70 = 1400 
3 tab x 1400 cases = 4200 tab 
Zinc sulfate 
20% 
2000 x 0.20 = 400 
10 tab x 400 cases = 4000 tab 
Buffer stock
A buffer stock of at least 2 weeks should be added from the start (and maintained for the duration of the epidemic). This period can be prolonged (e.g. 3 weeks) for zones that are difficult to access or in case of supply difficulties.
For example, in a refugee camp, 1500 patients are expected (21 patients per day at peak): add the treatment of 300 patients (21 cases x 14 days = 294 patients) or 20% of patients (300 = 20% of 1500). Among these 300 patients, 75% (225 patients) will be treated by oral route only and 25% (75 patients) by oral and IV route.
Total estimated quantities
Thus it is estimated that in this refugee camp the following may be needed during the epidemic (rounded quantities):

For expected cases 
Buffer stock 
Total 

ORS sachets 
15 000 
3000 
18 000 sachets of ORS 
RL litres 
3750 
750 
4500 litres of RL 
Infusion sets 
1900 
375 
2300 infusion sets 
Catheters 
1250 
250 
1500 catheters 