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Effectiveness of Ring Vaccination as Control Strategy for Ebola Virus Disease.

Kucharski AJ, Eggo RM, Watson CH, Camacho A, Funk S, Edmunds WJ - Emerging Infect. Dis. (2016)

Bottom Line: Using an Ebola virus disease transmission model, we found that addition of ring vaccination at the outset of the West Africa epidemic might not have led to containment of this disease.However, in later stages of the epidemic or in outbreaks with less intense transmission or more effective control, this strategy could help eliminate the disease.

View Article: PubMed Central - PubMed

ABSTRACT
Using an Ebola virus disease transmission model, we found that addition of ring vaccination at the outset of the West Africa epidemic might not have led to containment of this disease. However, in later stages of the epidemic or in outbreaks with less intense transmission or more effective control, this strategy could help eliminate the disease.

No MeSH data available.


Related in: MedlinePlus

Outbreak dynamics in a model of transmission of Ebola virus disease. A) Chains of transmission generated in a simulated outbreak starting with 2 infected persons on March 1, 2014. Black circles indicate the index case within each cluster, and arrows indicate routes of transmission. Within each cluster, we assumed that there was a 15% probability that a secondary case would be missed and would instead seed a new cluster (these missed links are not shown). B) New cases per week, by date of symptom onset, for the chains of transmission shown in panel A. Colors of clusters in panel A match colors of bars in panel B. C) Observed weekly confirmed and probable cases reported in Conakry Prefecture, Guinea, during March–September 2014. Data were obtained from the Guinea Ministry of Health and World Health Organization Situation Reports (11).
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Figure 1: Outbreak dynamics in a model of transmission of Ebola virus disease. A) Chains of transmission generated in a simulated outbreak starting with 2 infected persons on March 1, 2014. Black circles indicate the index case within each cluster, and arrows indicate routes of transmission. Within each cluster, we assumed that there was a 15% probability that a secondary case would be missed and would instead seed a new cluster (these missed links are not shown). B) New cases per week, by date of symptom onset, for the chains of transmission shown in panel A. Colors of clusters in panel A match colors of bars in panel B. C) Observed weekly confirmed and probable cases reported in Conakry Prefecture, Guinea, during March–September 2014. Data were obtained from the Guinea Ministry of Health and World Health Organization Situation Reports (11).

Mentions: In the model, transmission followed a branching process (8), and secondary cases were generated from a negative binomial distribution to include potential for superspreading events (6,9). Each cluster started with an index case, which generated an average of Rm = 7 secondary cases. Many EVD cases reported in Guinea were not part of already known transmission chains (Technical Appendix, Figure 2). We therefore assumed there was a probability ρ that a secondary case would missed and go on to seed an independent transmission cluster as an index case with Rm = 7. Otherwise, the case would remain within the known chain of transmission (with probability 1 – ρ); these cases would then generate an average of Rw = 0.66 secondary cases. The simulated outbreaks ended when, by chance, no secondary cases were generated by active cases. Distributions of incubation period, duration of infectiousness, and time to reporting were obtained from reported values for Guinea in 2014 (10). Model simulations produced similar patterns to those observed in 2014 (Figure 1). When half of the cases were missed, the overall reproduction number, defined as the mean number of secondary cases generated across all infectious persons, was ≈1.5, which was similar to values observed in early 2014 in West Africa (11) and in the initial stages of other outbreaks (Technical Appendix Table 1).


Effectiveness of Ring Vaccination as Control Strategy for Ebola Virus Disease.

Kucharski AJ, Eggo RM, Watson CH, Camacho A, Funk S, Edmunds WJ - Emerging Infect. Dis. (2016)

Outbreak dynamics in a model of transmission of Ebola virus disease. A) Chains of transmission generated in a simulated outbreak starting with 2 infected persons on March 1, 2014. Black circles indicate the index case within each cluster, and arrows indicate routes of transmission. Within each cluster, we assumed that there was a 15% probability that a secondary case would be missed and would instead seed a new cluster (these missed links are not shown). B) New cases per week, by date of symptom onset, for the chains of transmission shown in panel A. Colors of clusters in panel A match colors of bars in panel B. C) Observed weekly confirmed and probable cases reported in Conakry Prefecture, Guinea, during March–September 2014. Data were obtained from the Guinea Ministry of Health and World Health Organization Situation Reports (11).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4696719&req=5

Figure 1: Outbreak dynamics in a model of transmission of Ebola virus disease. A) Chains of transmission generated in a simulated outbreak starting with 2 infected persons on March 1, 2014. Black circles indicate the index case within each cluster, and arrows indicate routes of transmission. Within each cluster, we assumed that there was a 15% probability that a secondary case would be missed and would instead seed a new cluster (these missed links are not shown). B) New cases per week, by date of symptom onset, for the chains of transmission shown in panel A. Colors of clusters in panel A match colors of bars in panel B. C) Observed weekly confirmed and probable cases reported in Conakry Prefecture, Guinea, during March–September 2014. Data were obtained from the Guinea Ministry of Health and World Health Organization Situation Reports (11).
Mentions: In the model, transmission followed a branching process (8), and secondary cases were generated from a negative binomial distribution to include potential for superspreading events (6,9). Each cluster started with an index case, which generated an average of Rm = 7 secondary cases. Many EVD cases reported in Guinea were not part of already known transmission chains (Technical Appendix, Figure 2). We therefore assumed there was a probability ρ that a secondary case would missed and go on to seed an independent transmission cluster as an index case with Rm = 7. Otherwise, the case would remain within the known chain of transmission (with probability 1 – ρ); these cases would then generate an average of Rw = 0.66 secondary cases. The simulated outbreaks ended when, by chance, no secondary cases were generated by active cases. Distributions of incubation period, duration of infectiousness, and time to reporting were obtained from reported values for Guinea in 2014 (10). Model simulations produced similar patterns to those observed in 2014 (Figure 1). When half of the cases were missed, the overall reproduction number, defined as the mean number of secondary cases generated across all infectious persons, was ≈1.5, which was similar to values observed in early 2014 in West Africa (11) and in the initial stages of other outbreaks (Technical Appendix Table 1).

Bottom Line: Using an Ebola virus disease transmission model, we found that addition of ring vaccination at the outset of the West Africa epidemic might not have led to containment of this disease.However, in later stages of the epidemic or in outbreaks with less intense transmission or more effective control, this strategy could help eliminate the disease.

View Article: PubMed Central - PubMed

ABSTRACT
Using an Ebola virus disease transmission model, we found that addition of ring vaccination at the outset of the West Africa epidemic might not have led to containment of this disease. However, in later stages of the epidemic or in outbreaks with less intense transmission or more effective control, this strategy could help eliminate the disease.

No MeSH data available.


Related in: MedlinePlus