Evaluation of contingency actions to control the spread of raccoon rabies in Ohio and Virginia

The raccoon (Procyon lotor) variant of the rabies virus (RRV) is enzootic in the eastern United States and oral rabies vaccination (ORV) is the primary strategy to prevent and control landscape spread. Breaches of ORV management zones occasionally occur, and emergency "contingency" actions may be implemented to enhance local control. Contingency actions are an integral part of landscape-scale wildlife rabies management but can be very costly and routinely involve enhanced rabies surveillance (ERS) around the index case. We investigated two contingency actions in Ohio (2017-2019 and 2018-2021) and one in Virginia (2017-2019) using a dynamic, multi-method occupancy approach to examine relationships between specific management actions and RRV occurrence, including whether ERS was sufficient around the index case. The RRV occupancy was assessed seasonally at 100-km2 grids and we examined relationships across three spatial scales (regional management zone, RRV free regions, and local contingency areas). The location of a grid relative to the ORV management zone was the strongest predictor of RRV occupancy at the regional scale. In RRV free regions, the neighbor effect and temporal variability were most important in influencing RRV occupancy. Parenteral (hand) vaccination of raccoons was important across all three contingency action areas, but more influential in the Ohio contingency action areas where more raccoons were hand vaccinated. In the Virginia contingency action area, ORV strategies were as important in reducing RRV occupancy as a hand vaccination strategy. The management action to trap, euthanize, and test (TET) raccoons was an important method to increase ERS, yet the impacts of TET on RRV occupancy are not clear. The probability of detecting additional cases of RRV was exceptionally high (>0.95) during the season the index case occurred. The probability of detecting RRV through ERS declined in the seasons following initial TET efforts but remained higher after the contingency action compared to the ERS detection probabilities prior to index case incidence. Local RRV cases were contained within one year and eliminated within 2-3 years of each contingency action.

Mumps vaccine effectiveness of a 3rd dose of measles, mumps, rubella vaccine in school settings during a mumps outbreak -- Arkansas, 2016-2017

Objectives

The largest mumps outbreak in the United States since 2006 occurred in Arkansas during the 2016-17 school year. An additional dose (third dose) of measles-mumps-rubella vaccine (MMR3) was offered to school children. We evaluated the vaccine effectiveness (VE) of MMR3 compared with two doses of MMR for preventing mumps among school-aged children during the outbreak.

Study design

A generalized linear mixed effects model was used to estimate the incremental vaccine effectiveness (VE) of a third dose of MMR compared with two doses of MMR for preventing mumps.

Methods

We obtained school enrollment, immunization status and mumps case status from school registries, Arkansas's immunization registry, and Arkansas's mumps surveillance system, respectively. We included students who previously received 2 doses of MMR in schools with ≥1 mumps case after the MMR3 clinic. We used a generalized linear mixed model to estimate VE of MMR3 compared with two doses of MMR.

Results

Sixteen schools with 9272 students were included in the analysis. Incremental VE of MMR3 versus a two-dose MMR regimen was 52.7% (95% confidence interval [CI]: -3.6%‒78.4%) overall and in 8 schools with high mumps transmission it was 64.0% (95% CI: 1.2%‒86.9%). MMR3 VE was higher among middle compared with elementary school students (68.5% [95% CI: -30.2%‒92.4%] vs 37.6% [95% CI: -62.5%‒76.1%]); these differences were not statistically significant.

Conclusion

Our findings suggest MMR3 provided additional protection from mumps compared with two MMR doses in elementary and middle school settings during a mumps outbreak.

Effective contact tracing for COVID-19: A systematic review

Contact tracing is commonly recommended to control outbreaks of COVID-19, but its effectiveness is unclear. Following PRISMA guidelines, we searched four databases using a range of terms related to contact tracing effectiveness for COVID-19. We found 343 papers; 32 were included. All were observational or modelling studies. Observational studies (n = 14) provided consistent, very-low certainty evidence that contact tracing (alone or in combination with other interventions) was associated with better control of COVID-19 (e.g. in Hong Kong, only 1084 cases and four deaths were recorded in the first 4.5 months of the pandemic). Modelling studies (n = 18) provided consistent, high-certainty evidence that under assumptions of prompt and thorough tracing with effective quarantines, contact tracing could stop the spread of COVID-19 (e.g. by reducing the reproduction number from 2.2 to 0.57). A cautious interpretation indicates that to stop the spread of COVID-19, public health practitioners have 2-3 days from the time a new case develops symptoms to isolate the case and quarantine at least 80% of its contacts.

Managing host-parasite interactions in humans and wildlife in times of global change

Global change in the Anthropocene has modified the environment of almost any species on earth, be it through climate change, habitat modifications, pollution, human intervention in the form of mass drug administration (MDA), or vaccination. This can have far-reaching consequences on all organisational levels of life, including eco-physiological stress at the cell and organism level, individual fitness and behaviour, population viability, species interactions and biodiversity. Host-parasite interactions often require highly adapted strategies by the parasite to survive and reproduce within the host environment and ensure efficient transmission among hosts. Yet, our understanding of the system-level outcomes of the intricate interplay of within host survival and among host parasite spread is in its infancy. We shed light on how global change affects host-parasite interactions at different organisational levels and address challenges and opportunities to work towards better-informed management of parasite control. We argue that global change affects host-parasite interactions in wildlife inhabiting natural environments rather differently than in humans and invasive species that benefit from anthropogenic environments as habitat and more deliberate rather than erratic exposure to therapeutic drugs and other control efforts.

Lessons from past pandemics: a systematic review of evidence-based, cost-effective interventions to suppress COVID-19

BACKGROUND

In an unparalleled global response, during the COVID-19 pandemic, 90 countries asked 3.9 billion people to stay home. Yet other countries avoided lockdowns and focused on other strategies, like contact tracing. How effective and cost-effective are these strategies? We aimed to provide a comprehensive summary of the evidence on past pandemic controls, with a focus on cost-effectiveness.

METHODS

Following PRISMA guidelines, MEDLINE (1946 to April week 2, 2020) and EMBASE (1974 to April 17, 2020) were searched using a range of terms related to pandemic control. Articles reporting on the effectiveness or cost-effectiveness of at least one intervention were included.

RESULTS

We found 1653 papers; 62 were included. The effectiveness of hand-washing and face masks was supported by randomized trials. These measures were highly cost-effective. For other interventions, only observational and modelling studies were found. They suggested that (1) the most cost-effective interventions are swift contact tracing and case isolation, surveillance networks, protective equipment for healthcare workers, and early vaccination (when available); (2) home quarantines and stockpiling antivirals are less cost-effective; (3) social distancing measures like workplace and school closures are effective but costly, making them the least cost-effective options; (4) combinations are more cost-effective than single interventions; and (5) interventions are more cost-effective when adopted early. For 2009 H1N1 influenza, contact tracing was estimated to be 4363 times more cost-effective than school closure ($2260 vs. $9,860,000 per death prevented).

CONCLUSIONS AND CONTRIBUTIONS

For COVID-19, a cautious interpretation suggests that (1) workplace and school closures are effective but costly, especially when adopted late, and (2) scaling up as early as possible a combination of interventions that includes hand-washing, face masks, ample protective equipment for healthcare workers, and swift contact tracing and case isolation is likely to be the most cost-effective strategy.

A comprehensive approach to ending an outbreak of rare blaOXA-72 gene-positive carbapenem-resistant Acinetobacter baumannii at a Community Hospital, Kansas City, MO, 2018

We identified a cluster of extensively drug-resistant, carbapenemase gene-positive, carbapenem-resistant Acinetobacter baumannii (CP-CRAB) at a teaching hospital in Kansas City. Extensively drug-resistant CRAB was identified from eight patients and 3% of environmental cultures. We used patient cohorting and targeted environmental disinfection to stop transmission. After implementation of these measures, no additional cases were identified.

Health technology assessment applied to emergency preparedness: a new perspective

Emergency preparedness is a continuous quality improvement process through which roles and responsibilities are defined to effectively anticipate, respond to, and recover from the impact of emergencies. This process results in documented plans that provide a backbone structure for developing the core capacities to address health threats. Nevertheless, several barriers can impair an effective preparedness planning, as it needs a 360° perspective to address each component according to the best evidence and practice. Preparedness planning shares common principles with health technology assessment (HTA) as both encompass a multidisciplinary and multistakeholder approach, follow an iterative cycle, adopt a 360° perspective on the impact of intervention measures, and conclude with decision-making support. Our "Perspective" illustrates how each HTA domain can address different component(s) of a preparedness plan that can indeed be seen as a container of multiple HTAs, which can then be used to populate the entire plan itself. This approach can allow one to overcome preparedness barriers, providing an independent, systematic, and robust tool to address the components and ensuring a comprehensive evaluation of their value in the mitigation of the impact of emergencies.

Vaccination and Therapeutics: Responding to the Changing Epidemiology of Yellow Fever

At the turn of the nineteenth century, yellow fever (YF) was considered the most dangerous infectious disease with high case fatality. Subsequent, mass vaccination campaigns coupled with widespread elimination of the YF mosquito vector significantly decreased YF cases and reduced outbreaks to the tropical and subtropical forested regions of Africa and South America. However, recent (2016) large outbreaks in Angola, Democratic Republic of Congo (DRC), and South-Eastern Brazil, where previously had been demarcated as low-risk regions, have highlighted the possibility of a rapidly changing epidemiology and the potential re-emergence of yellow fever virus (YFV). Furthermore, the first-ever importation of YFV into Asia has highlighted the potential fear of YFV emerging as a global threat. In this review, we describe the changing epidemiology of YF outbreaks, and highlight the use of public health policies, therapeutics, and vaccination as tools to help eliminate future YFV outbreaks.

The effect of preventing subclinical transmission on the containment of COVID-19: Mathematical modeling and experience in Taiwan

The control strategies preventing subclinical transmission differed among countries. A stochastic transmission model was used to assess the potential effectiveness of control strategies at controlling the COVID-19 outbreak. Three strategies included lack of prevention of subclinical transmission (Strategy A), partial prevention using testing with different accuracy (Strategy B) and complete prevention by isolating all at-risk people (Strategy C, Taiwan policy). The high probability of containing COVID-19 in Strategy C is observed in different scenario, had varied in the number of initial cases (5, 20, and 40), the reproduction number (1.5, 2, 2.5, and 3.5), the proportion of at-risk people being investigated (40%, 60%, 80%, to 90%), the delay from symptom onset to isolation (long and short), and the proportion of transmission that occurred before symptom onset (<1%, 15%, and 30%). Strategy C achieved probability of 80% under advantageous scenario, such as low number of initial cases and high coverage of epidemiological investigation but Strategy B and C rarely achieved that of 60%. Considering the unsatisfactory accuracy of current testing and insufficient resources, isolation of all at-risk people, as adopted in Taiwan, could be an effective alternative.

Vaccination and Therapeutics: Responding to the Changing Epidemiology of Yellow Fever

Purpose of Review

At the turn of the nineteenth century, yellow fever (YF) was considered the most dangerous infectious disease with high case fatality. Subsequent, mass vaccination campaigns coupled with widespread elimination of the YF mosquito vector significantly decreased YF cases and reduced outbreaks to the tropical and subtropical forested regions of Africa and South America.

Recent Findings

However, recent (2016) large outbreaks in Angola, Democratic Republic of Congo (DRC), and South-Eastern Brazil, where previously had been demarcated as low-risk regions, have highlighted the possibility of a rapidly changing epidemiology and the potential re-emergence of yellow fever virus (YFV). Furthermore, the first-ever importation of YFV into Asia has highlighted the potential fear of YFV emerging as a global threat.

Summary

In this review, we describe the changing epidemiology of YF outbreaks and highlight the use of public health policies, therapeutics, and vaccination as tools to help eliminate future YFV outbreaks.

Management of a COVID-19 outbreak in a hotel in Tenerife, Spain

Since the first accounts of SARS-CoV-2, authorities have encountered numerous unprecedented situations threatening public health. This rapid communication addresses events that led to the quarantining of a hotel in Tenerife, Spain and the effectiveness of the rapidly implemented control measures. In total, eight cases have been associated with the hotel. Due to the international nature of the guests, had these timely precautions not been in place, a multinational cluster might have formed.

Nosocomial Outbreak Caused by NDM-5 and OXA-181 Carbapenemase Co-producing Escherichia coli

Carbapenemase-producing Enterobacteriaceae (CPE) is an important and increasing threat to global health. From July to September 2017, 20 inpatients at a tertiary care hospital in Korea were either colonized or infected with carbapenem-resistant Escherichia coli strains. All of E. coli isolates co-produced bla_NDM-5 and bla_OXA-181 carbapenemase genes and shared ≥88% clonal relatedness on the basis of a cladistic calculation of the distribution of pulsed-field gel electrophoresis patterns. Rapid detection of CPE is one of the most important factors to prevent CPE dissemination because it takes long time for CPE to become negative.

Control of Ebola virus disease outbreaks: Comparison of health care worker-targeted and community vaccination strategies

BACKGROUND

Health care workers (HCW) are at risk of infection during Ebola virus disease outbreaks and therefore may be targeted for vaccination before or during outbreaks. The effect of these strategies depends on the role of HCW in transmission which is understudied.

METHODS

To evaluate the effect of HCW-targeted or community vaccination strategies, we used a transmission model to explore the relative contribution of HCW and the community to transmission. We calibrated the model to data from multiple Ebola outbreaks. We quantified the impact of ahead-of-time HCW-targeted strategies, and reactive HCW and community vaccination.

RESULTS

We found that for some outbreaks (we call "type 1″) HCW amplified transmission both to other HCW and the community, and in these outbreaks prophylactic vaccination of HCW decreased outbreak size. Reactive vaccination strategies had little effect because type 1 outbreaks ended quickly. However, in outbreaks with longer time courses ("type 2 outbreaks"), reactive community vaccination decreased the number of cases, with or without prophylactic HCW-targeted vaccination. For both outbreak types, we found that ahead-of-time HCW-targeted strategies had an impact at coverage of 30%.

CONCLUSIONS

The vaccine strategies tested had a different impact depending on the transmission dynamics and previous control measures. Although we will not know the characteristics of a new outbreak, ahead-of-time HCW-targeted vaccination can decrease the total outbreak size, even at low vaccine coverage.

Nosocomial outbreak of Candida parapsilosis sensu stricto fungaemia in a neonatal intensive care unit in China

BACKGROUND

Candida parapsilosis is a common agent of fungaemia, but few outbreaks of Candida parapsilosis infection have been reported in China.

AIM

To elaborate an outbreak of nosocomial Candida parapsilosis sensu stricto fungaemia in a neonatal intensive care unit (NICU) of a comprehensive hospital in China from July to October 2017.

METHODS

Epidemics and characteristics of fungaemia cases were investigated. Surveillance samples were collected. Vitek 2 Compact System, internal transcribed spacer sequencing, and random amplified polymorphic DNA (RAPD) typing were conducted to identify the isolates. Antifungal susceptibility test was performed for all bloodstream isolates.

FINDINGS

Sixteen neonates were diagnosed as Candida parapsilosis sensu stricto fungaemia during this period. Presenting symptoms included leucopenia, thrombocytopenia, and respiratory crackles. Fifteen cases were cured whereas one case who suffered from severe concomitant diseases died. The isolates were susceptible to fluconazole, amphotericin B, itraconazole, voriconazole, and 5-fluorocytosine. A total of 313 surveillance samples were collected, and Candida parapsilosis sensu stricto was identified from 16 environmental samples and one sample from an ultrasonographer's hand. The colonized locations included wiping cloths, faucets, sinks, operating table, puddles in the bathroom, a ventilator, and an ultrasonic probe. The RAPD patterns of all the Candida parapsilosis sensu stricto isolates from bloodstream and surveillance samples were identical. The outbreak was controlled after a series of infection control measures.

CONCLUSION

Contaminated environment was associated with this outbreak. Close attention to immunocompromised patients, thorough environmental disinfection and hand hygiene should be strengthened in NICU.

Estimating the scale of adverse animal welfare consequences of movement restriction and mitigation strategies in a classical swine fever outbreak

Background

The study aim was to quantify the impact of movement restriction on the well-being of pigs and the associated mitigation responses during a classical swine fever (CSF) outbreak. We developed a stochastic risk assessment model and incorporated Indiana swine industry statistics to estimate the timing and number of swine premises that would encounter overcrowding or feed interruption resulting from movement restriction. Our model also quantified the amount of on-farm euthanasia and movement of pigs to slaughter plants required to alleviate those conditions. We simulated various single-site (i.e., an outbreak initiated from one location) and multiple-site (i.e., an outbreak initiated from more than one location) outbreak scenarios in Indiana to estimate outputs.

Results

The study estimated that 14% of the swine premises in Indiana would encounter overcrowding or feed interruption due to movement restriction implemented during a CSF outbreak. The number of premises that would experience animal welfare conditions was about 2.5 fold of the number of infected premises. On-farm euthanasia needed to be performed on 33% of those swine premises to alleviate adverse animal welfare conditions, and more than 90% of on-farm euthanasia had to be carried out within 2 weeks after the implementation of movement restriction. Conversely, movement of pigs to slaughter plants could alleviate 67% of adverse animal welfare conditions due to movement restriction, and only less than 1% of movement of pigs to slaughter plants had to be initiated in the first 2 weeks of movement restrictions. The risk of secondary outbreaks due to movement of pigs from movement restriction areas to slaughter plants was low and only seven pigs from each shipment needed to be tested for CSF infection to prevent a secondary outbreak.

Conclusions

We found that the scale of adverse animal welfare consequences of movement restriction during a CSF outbreak in Indiana was substantial, and controlled movement of pigs to slaughter plants was an efficient and low-risk alternative mitigation response to on-farm euthanasia. The output estimates generated from this study provide empirical evidence for decision makers to properly incorporate required resources for mitigating adverse animal welfare conditions in CSF outbreak management strategic planning.

Middle East respiratory syndrome in South Korea during 2015: Risk-related perceptions and quarantine attitudes

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Korean public had low trust in the government for controlling the MERS outbreak.

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Korean public perceived low risk from contracting MERS during the MERS outbreak.

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Most Korean public believed that quarantine was ineffective to control MERS.

A telephone survey involving 200 household members in and around Seoul, South Korea, was completed during the maturity stage of the outbreak of Middle East respiratory syndrome (MERS) in Korea during June 2015. The study found that respondents perceived low risk from contracting MERS, had low trust in government in controlling MERS, and generally held unfavorable attitudes toward quarantine.

A practical community-based response strategy to interrupt Ebola transmission in sierra Leone, 2014-2015

Background

The Ebola virus disease spread rapidly in West Africa in 2014, leading to the loss of thousands of lives. Community engagement was one of the key strategies to interrupt Ebola transmission, and practical community level measures needed to be explored in the field and tailored to the specific context of communities.

Methods

First, community-level education on Ebola virus disease (EVD) prevention was launched for the community’s social mobilizers in six districts in Sierra Leone beginning in November 2014. Then, from January to May of 2015, in three pilot communities, local trained community members were organized to engage in implementation of EVD prevention and transmission interruption measures, by involving them in alert case report, contact tracing, and social mobilization. The epidemiological indicators of transmission interruption in three study communities were evaluated.

Results

A total of 6 016 community social mobilizers from 185 wards were trained by holding 279 workshops in the six districts, and EVD message reached an estimated 631 680 residents. In three pilot communities, 72 EVD alert cases were reported, with 70.8 % of them detected by trained local community members, and 14 EVD cases were finally identified. Contact tracing detected 64.3 % of EVD cases. The median duration of community infectivity for the cases was 1 day. The secondary attack rate was 4.2 %, and no third generation of infection was triggered. No health worker was infected, and no unsafe burial and noncompliance to EVD control measures were recorded. The community-based measures were modeled to reduce 77 EVD cases, and the EVD-free goal was achieved four months earlier in study communities than whole country of Sierra Leone.

Conclusions

The community-based strategy of social mobilization and community engagement was effective in case detection and reducing the extent of Ebola transmission in a country with weak health system. The successfully practical experience to reduce the risk of Ebola transmission in the community with poor resources would potentially be helpful for the global community to fight against the EVD and the other diseases in the future.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-016-0167-0) contains supplementary material, which is available to authorized users.

Collaborative Intervention of Middle East Respiratory Syndrome: Rapid Response Team

On May 20th 2015, a 68 year old man was the first to be diagnosed with Middle East Respiratory Syndrome-Corona Virus (MERS-CoV) in Korea. He travelled to Bahrain, Saudi Arabia, and Qatar for 16 days. On May 4th 2015, the patient entered Korea, with febrile sense and respiratory symptoms that appeared on May 11th. The MERS-CoV Outbreak became worse and several patients had to be admitted throughout various hospitals starting at the beginning of June. This situation led to a nationwide chaos. The Rapid Response Team (RRT) was organized after the Korean government's calling for specialists that were composed of 15 Infectious disease Doctors and 2 Infection Control professionals on the 8th of June 2015. The main purpose of the RRT were: 1) consultation to the Government controlling MERS-CoV outbreak. 2) Visit hospitals that were exposed to MERS-CoV infected patients, and to provide advice regarding infection control strategy for rehabilitating of the exposed hospitals. Since June 8th, the RRT visited more than 10 hospitals and an effective consultation was carried out. Most of the hospitals were recovering from the MERS outbreak since early July. Cooperation between the government and private sector experts was very effective. The efforts of government and private sector experts overcame the initial chaos situation. It could prevent further deterioration of the MERS outbreak.

Outcomes, Approaches, and Challenges to Developing and Passing a Countywide Mandatory Vaccination Policy: St. Louis County's Experience with Hepatitis A Vaccine for Food Service Personnel

In the early 1990s, St. Louis County had multiple foodservice worker-related hepatitis A outbreaks uncontrolled by standard outbreak interventions. Restaurant interest groups and the general public applied political pressure to local public health officials for more stringent interventions, including a mandatory vaccination policy. Local health departments can enact mandatory vaccination policies, but this has rarely been done. The study objectives were to describe the approach used to pass a mandatory vaccination policy at the local jurisdiction level and illustrate the outcome from this ordinance 15 years later. A case study design was used. In-depth, semi-structured interviews using guided questions were conducted in spring, 2015, with six key informants who had direct knowledge of the mandatory vaccination policy process. Meeting minutes and/or reports were also analyzed. A Poisson distribution analysis was used to calculate the rate of outbreaks before and after mandatory vaccination policy implementation. The policy appears to have reduced the number of hepatitis A outbreaks, lowering the morbidity and economic burden in St. Louis County. The lessons learned by local public health officials in passing a mandatory hepatitis A vaccination policy are important and relevant in today's environment. The experience and lessons learned may assist other local health departments when faced with the potential need for mandatory policies for any vaccine preventable disease.

Disinfecting personal protective equipment with pulsed xenon ultraviolet as a risk mitigation strategy for health care workers

The doffing of personal protective equipment (PPE) after contamination with pathogens such as Ebola poses a risk to health care workers. Pulsed xenon ultraviolet (PX-UV) disinfection has been used to disinfect surfaces in hospital settings. This study examined the impact of PX-UV disinfection on an Ebola surrogate virus on glass carriers and PPE material to examine the potential benefits of using PX-UV to decontaminate PPE while worn, thereby reducing the pathogen load prior to doffing. Ultraviolet (UV) safety and coverage tests were also conducted. PX-UV exposure resulted in a significant reduction in viral load on glass carriers and PPE materials. Occupational Safety and Health Administration-defined UV exposure limits were not exceeded during PPE disinfection. Predoffing disinfection with PX-UV has potential as an additive measure to the doffing practice guidelines. The PX-UV disinfection should not be considered sterilization; all PPE should still be considered contaminated and doffed and disposed of according to established protocols.

Speed versus coverage trade off in targeted interventions during an outbreak

Which case-based intervention measures should be applied during an epidemic outbreak depends on how timely they can be applied and how effective they are. During the course of each individual's infection, the earlier control measures are applied on him/her the more effectively further disease spread can be prevented. However, quick implementation can lead to loss of efficacy or coverage, e.g., when individuals are targeted based on rapid but poorly sensitive diagnostic tests in place of slower but accurate PCR tests. To analyse this trade off between speed and coverage we used stochastic models considering how the individual reproduction density is modified by interventions. We took as example the case-based intervention strategy employed in the Netherlands during the beginning of the H1N1 pandemic. Suspected cases were isolated and samples were collected for PCR diagnosis. In case of positive diagnosis, antiviral drugs were provided to contacts as post-exposure prophylaxis. At the time there were also rapid influenza diagnostic tests (RIDTs) available which provided results within an hour after sample collection compared to a median of 2.7 days for PCR tests, but they were less sensitive. We studied how interventions based on RIDTs with various sensitivities affect the outbreak size and how these compare to PCR diagnosis based interventions. Using an intervention based on a bedside RIDT with 60% detection ratio or a laboratory RIDT with 70% detection ratio is as effective as the most effective PCR-diagnosis based intervention. Relative performances of interventions are not dependent on the basic reproduction number R0 but only on distributions of individual reproduction density and of delay periods. The individual reproduction density combines R0 and infection time distribution, both crucial in determining the impact of case-based interventions during epidemic outbreaks.