2.7 Estimation of treatment resource needs
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 at-risk 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:
– 25-30% of patients will have severe dehydration, 30-40% some dehydration, and 30-40% 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 15-20% 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, 8-10 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 |