Small Outbreaks Research Articles

B-275 Retrospective Study for Mpox Detection: Validation of a Real Time PCR Kit for its Fast Diagnosis

Abstract Background In an increasingly globalised and interconnected world, a small outbreak of an infectious disease (such as monkeypox in 2022) can turn into a global health emergency. In this context, global health systems must develop effective strategies to interrupt transmission as early as possible by identifying cases and sources of infection. Since clinical diagnostic products must be externally validated to comply with current regulations, the aim of this collaborative and retrospective study was to evaluate the clinical sensitivity and specificity of the VIASURE Monkey pox Real time PCR detection kit (CerTest Biotec) for the detection of monkeypox by Real time PCR. Methods This is a retrospective and collaborative study conducted at the Microbiology Department of the Miguel Servet University Hospital at the request of the company Certest Biotec SL with the approvement of the Aragon research ethics committee (PI22/412; 5 Oct 2022). A total of 192 suspected MPX samples were collected in 2022–2023. RealStar Orthopoxvirus PCR kit 1.0, Altona Diagnostics and Sanger sequencing were used as reference techniques. Clinical sensitivity and specificity (95% CI) were calculated with MetaDisc 1.4 software, while overall concordance and quantitative correlation between both real-time PCR kits was checked with the statistical package SPSS v24 (IBM Corporation). Results All the results obtained by the kit under study coincided with the reference kit ones (being 69 of them positives for monkeypox). Therefore, clinical sensitivity and specificity values are 100%. Furthermore, the overall agreement was almost perfect (100, 98–100) as was the Spearman correlation test (rs = 0.78; P < 0.001). All positive samples were sequenced and confirmed the presence of the virus. Conclusion This retrospective study demonstrates the good clinical parameters and strong overall agreement of the VIASURE® Monkey pox virus Real Time PCR detection kit (CerTest Biotec) compared to both the RealStar Orthopoxvirus PCR 1.0 kit and Sanger sequencing results. In addition, the stabilised, ready-to-use format allows storage at room temperature, and facilitates transport, as it does not need to be refrigerated. This makes it environmentally friendly and reduces additional costs.

Cruise subsidy strategies in the post COVID-19 era: Refund risk, low-price dilemma

The COVID-19 pandemic has completely devastated the cruise industry in the past three years. Although the cruise market has gained hope for recovery with adequate control of the COVID-19 epidemic worldwide, small outbreaks in local areas will still bring passengers and cruise lines a greater risk of ticket refunds, affecting the recovery of the cruise market. Therefore, governments and cruise lines should respond to these challenges by making adequate efforts to promote the revival of the cruise market. Using the Chinese cruise market as an example, we propose a cruise supply chain system that considers the risk of refunds and sets an upper limit for the government's subsidy budget to investigate the optimal subsidy strategy in the post-COVID-19 era. Our results show that subsidizing cruise lines is the best way to maximize market demand. However, subsidizing passengers is a better choice to prevent the Chinese cruise market from falling into the low-price dilemma. Fortunately, when the government's subsidy budget is not high, and the epidemic situation is optimistic (i.e., the risk of refund is low), if the brand advantage of the international cruise is high enough, subsidizing the cruise line can ensure the healthy development of the cruise market while expanding market demand more effectively. This conclusion will guide the transformation and upgrading of the Chinese cruise market.

Randomness accelerates the dynamic clearing process of the COVID-19 outbreaks in China

During the implementation of strong non-pharmaceutical interventions (NPIs), more than one hundred COVID-19 outbreaks induced by different strains in China were dynamically cleared in about 40 days, which presented the characteristics of small scale clustered outbreaks with low peak levels. To address how did randomness affect the dynamic clearing process, we derived an iterative stochastic difference equation for the number of newly reported cases based on the classical stochastic SIR model and calculate the stochastic control reproduction number (SCRN). Further, by employing the Bayesian technique, the change points of SCRNs have been estimated, which is an important prerequisite for determining the lengths of the exponential growth and decline phases. To reveal the influence of randomness on the dynamic zeroing process, we calculated the explicit expression of the mean first passage time (MFPT) during the decreasing phase using the relevant theory of first passage time (FPT), and the main results indicate that random noise can accelerate the dynamic zeroing process. This demonstrates that powerful NPI measures can rapidly reduce the number of infected people during the exponential decline phase, and enhanced randomness is conducive to dynamic zeroing, i.e. the greater the random noise, the shorter the average clearing time is. To confirm this, we chose 26 COVID-19 outbreaks in various provinces in China and fitted the data by estimating the parameters and change points. We then calculated the MFPTs, which were consistent with the actual duration of dynamic zeroing interventions.

An optimal mechanism to fund the development of vaccines against emerging epidemics

We derive the optimal funding mechanism to incentivize development and production of vaccines against diseases with epidemic potential. In the model, suppliers’ costs are private information and investments are noncontractible, precluding cost-reimbursement contracts, requiring fixed-price contracts conditioned on delivery of a successful product. The high failure risk for individual vaccines calls for incentivizing multiple entrants, accomplished by the optimal mechanism, a (w+1)-price reverse Vickrey auction with reserve, where w is the number of selected entrants. Our analysis determines the optimal number of entrants and required funding level. Based on a distribution of supplier costs estimated from survey data, we simulate the optimal mechanism’s performance in scenarios ranging from a small outbreak, causing harm in the millions of dollars, to the Covid-19 pandemic, causing harm in the trillions. We assess which mechanism features contribute most to its optimality.

Marburg virus: a potential outbreak on the horizon?

Marburg virus: a potential outbreak on the horizon?

Widespread Detection of Yersiniabactin Gene Cluster and Its Encoding Integrative Conjugative Elements (ICEKp) among Nonoutbreak OXA-48-Producing Klebsiella pneumoniae Clinical Isolates from Spain and the Netherlands.

In this study, we determined the presence of virulence factors in nonoutbreak, high-risk clones and other isolates belonging to less common sequence types associated with the spread of OXA-48-producing Klebsiella pneumoniae clinical isolates from The Netherlands (n = 61) and Spain (n = 53). Most isolates shared a chromosomally encoded core of virulence factors, including the enterobactin gene cluster, fimbrial fim and mrk gene clusters, and urea metabolism genes (ureAD). We observed a high diversity of K-Locus and K/O loci combinations, KL17 and KL24 (both 16%), and the O1/O2v1 locus (51%) being the most prevalent in our study. The most prevalent accessory virulence factor was the yersiniabactin gene cluster (66.7%). We found seven yersiniabactin lineages-ybt 9, ybt 10, ybt 13, ybt 14, ybt 16, ybt 17, and ybt 27-which were chromosomally embedded in seven integrative conjugative elements (ICEKp): ICEKp3, ICEKp4, ICEKp2, ICEKp5, ICEKp12, ICEKp10, and ICEKp22, respectively. Multidrug-resistant lineages-ST11, ST101, and ST405-were associated with ybt 10/ICEKp4, ybt 9/ICEKp3, and ybt 27/ICEKp22, respectively. The fimbrial adhesin kpi operon (kpiABCDEFG) was predominant among ST14, ST15, and ST405 isolates, as well as the ferric uptake system kfuABC, which was also predominant among ST101 isolates. No convergence of hypervirulence and resistance was observed in this collection of OXA-48-producing K. pneumoniae clinical isolates. Nevertheless, two isolates, ST133 and ST792, were positive for the genotoxin colibactin gene cluster (ICEKp10). In this study, the integrative conjugative element, ICEKp, was the major vehicle for yersiniabactin and colibactin gene clusters spreading. IMPORTANCE Convergence of multidrug resistance and hypervirulence in Klebsiella pneumoniae isolates has been reported mostly related to sporadic cases or small outbreaks. Nevertheless, little is known about the real prevalence of carbapenem-resistant hypervirulent K. pneumoniae since these two phenomena are often separately studied. In this study, we gathered information on the virulent content of nonoutbreak, high-risk clones (i.e., ST11, ST15, and ST405) and other less common STs associated with the spread of OXA-48-producing K. pneumoniae clinical isolates. The study of virulence content in nonoutbreak isolates can help us to expand information on the genomic landscape of virulence factors in K. pneumoniae population by identifying virulence markers and their mechanisms of spread. Surveillance should focus not only on antimicrobial resistance but also on virulence characteristics to avoid the spread of multidrug and (hyper)virulent K. pneumoniae that may cause untreatable and more severe infections.

An Outbreak of Limping Syndrome Associated with Feline Calicivirus.

Feline calicivirus (FCV) is a common viral pathogen found in domestic cats. FCV is highly contagious and demonstrates a high genetic variability. Upper respiratory tract disease, oral ulcerations, salivation, and gingivitis-stomatitis have been regarded as typical clinical signs of FCV infection. Ulcerative dermatitis, abortion, severe pneumonia, enteritis, chronic stomatitis, and virulent systemic disease have been reported more sporadically. Limping syndrome has been also described either in naturally or experimentally FCV-infected cats. In this study, we monitored a small outbreak of FCV infection in two household cats, in which limping disease was monitored with a 12-day lag time. The complete genome sequence was determined for the viruses isolated from the oropharyngeal and rectal swabs of the two animals, mapping up to 39 synonymous nucleotide mutations. The four isolates were sensitive to low pH conditions and trypsin treatment, a pattern usually associated with viruses isolated from the upper respiratory tract. Overall, the asynchronous pattern of infections and the results of genome sequencing suggest that a virus of respiratory origin was transmitted between the animals and that the FCV strain was able to retain the limping disease pathotype during the transmission chain, as previously observed in experimental studies with FCV strains associated with lameness.

Epidemic control in networks with cliques.

Social units, such as households and schools, can play an important role in controlling epidemic outbreaks. In this work, we study an epidemic model with a prompt quarantine measure on networks with cliques (a clique is a fully connected subgraph representing a social unit). According to this strategy, newly infected individuals are detected and quarantined (along with their close contacts) with probability f. Numerical simulations reveal that epidemic outbreaks in networks with cliques are abruptly suppressed at a transition point f_{c}. However, small outbreaks show features of a second-order phase transition around f_{c}. Therefore, our model can exhibit properties of both discontinuous and continuous phase transitions. Next, we show analytically that the probability of small outbreaks goes continuously to 1 at f_{c} in the thermodynamic limit. Finally, we find that our model exhibits a backward bifurcation phenomenon.

Immunopathogenesis of Nipah Virus Infection and Associated Immune Responses

Pandemics in the last two centuries have been initiated by causal pathogens that include Severe Acute Coronavirus 2 (SARS-CoV-2) and Influenza (e.g., the H1N1 pandemic of 2009). The latter is considered to have initiated two prior pandemics in 1918 and 1977, known as the “Spanish Flu” and “Russian Flu”, respectively. Here, we discuss other emerging infections that could be potential public health threats. These include Henipaviruses, which are members of the family Paramyxoviridae that infect bats and other mammals. Paramyxoviridae also include Parainfluenza and Mumps viruses (Rubulavirus) but also Respiratory Syncytial virus (RSV) (Pneumovirus). Additionally included is the Measles virus, recorded for the first time in writing in 1657 (Morbillivirus). In humans and animals, these may cause encephalitis or respiratory diseases. Recently, two more highly pathogenic class 4 viral pathogens emerged. These were named Hendra Henipavirus (HeV) and Nipah Henipavirus (NiV). Nipah virus is a negative-sense single-stranded ribonucleic acid ((−) ssRNA) virus within the family Paramyxoviridae. There are currently no known therapeutics or treatment regimens licensed as effective in humans, with development ongoing. Nipah virus is a lethal emerging zoonotic disease that has been neglected since its characterization in 1999 until recently. Nipah virus infection occurs predominantly in isolated regions of Malaysia, Bangladesh, and India in small outbreaks. Factors that affect animal–human disease transmission include viral mutation, direct contact, amplifying reservoirs, food, close contact, and host cell mutations. There are different strains of Nipah virus, and small outbreaks in humans limit known research and surveillance on this pathogen. The small size of outbreaks in rural areas is suggestive of low transmission. Person-to-person transmission may occur. The role that zoonotic (animal–human) or host immune system cellular factors perform therefore requires analysis. Mortality estimates for NiV infection range from 38–100% (averaging 58.2% in early 2019). It is therefore critical to outline treatments and prevention for NiV disease in future research. The final stages of the disease severely affect key organ systems, particularly the central nervous system and brain. Therefore, here we clarify the pathogenesis, biochemical mechanisms, and all research in context with known immune cell proteins and genetic factors.

Molecular Characterization and Phylogenetic Analysis of Dengue Fever Viruses in Three Outbreaks in Tanzania Between 2017 and 2019.

Dengue is a disease of public health interest, and Tanzania experienced major outbreaks in 2014 and 2019. Here, we report our findings on the molecular characterization of dengue viruses (DENV) that circulated during two smaller outbreaks (2017 and 2018) and one major epidemic (2019) in Tanzania. We tested archived serum samples from 1,381 suspected dengue fever patients, with a median age of 29 (IQR:22-40) years, referred to the National Public Health Laboratory for confirmation of DENV infection. DENV serotypes were identified by reverse transcription polymerase chain reaction (RT-PCR), and specific genotypes were identified by sequencing the envelope glycoprotein gene and phylogenetic inference methods. DENV was confirmed in 823 (59.6%) cases. More than half (54.7%) of patients with dengue fever infection were males, and nearly three-quarters (73%) of the infected individuals were living in Kinondoni district, Dar es Salaam. DENV-3 Genotype III caused the two smaller outbreaks in 2017 and 2018, while DENV-1 Genotype V caused the 2019 epidemic. DENV-1 Genotype I was also detected in one patient in 2019. This study has demonstrated the molecular diversity of dengue viruses circulating in Tanzania. We found that contemporary circulating serotypes did not cause the major epidemic of 2019 but rather due to a serotype shift from DENV-3 (2017/2018) to DENV-1 in 2019. Such a change increases the risk for patients previously infected with a particular serotype to develop severe symptoms upon potential re-infection with a heterologous serotype due to antibody-dependent enhancement of infection. Therefore, the circulation of serotypes emphasizes the need to strengthen the country's dengue surveillance system for better management of patients, early detection of outbreaks, and vaccine development.

Cross-sectional study of hepatitis E virus (HEV) circulation in Italian pig farms.

Foodborne transmission is considered the main way of spreading zoonotic hepatitis E virus (HEV) infection in Europe. In recent years, the human cases of hepatitis E in subjects without history of travel in endemic areas have raised, suggesting that domestic HEV transmission is increasing. Pork products with or without liver, are often indicated as the source of many human foodborne HEV cases as well as small outbreaks. Pigs are recognized as the main reservoir of the zoonotic HEV-3 genotype, the most frequently detected in human cases in the EU. In the absence of a harmonized surveillance of HEV circulation, data on prevalence are heterogeneous but confirm a widespread circulation of HEV-3 in pig herds across EU. HEV-3 can pass through the food chain from farm to fork when infected animals are slaughtered. In Italy, several studies reported the circulation of HEV-3 in pig farms, but results are heterogeneous due to different methodologies applied. In the present study, we performed a survey over 51 pig herds belonging to three main types of farms: breeding, fattening and farrow-to-finish. HEV-RNA was analyzed by broad range Real-time RT-PCR on 20 samples for each farm, obtained by pooling together feces from 10 individuals. Overall, HEV RNA was confirmed on 150 fecal pooled samples out of 1,032 (14.5%). At least one positive pooled sample was detected from 18 farms out of 51 tested (35.3%). By lowering the number of infected pigs at primary production, the risk of HEV-3 entering into the food chain can be reduced. Hence, information on HEV circulation in herds is highly relevant for choosing preventive measures and deserves development of a monitoring program and further investigations.

Coconut rhinoceros beetle in Solomon Islands: a tale of two invasions

Coconut rhinoceros beetle (Oryctes rhinoceros; CRB) was discovered in 2015 in a small outbreak in Honiara, Guadalcanal, Solomon Islands. This was the first record of CRB from Solomon Islands and a response plan was prepared. An awareness programme was launched and where CRB sightings were confirmed, delimitation surveys were carried out. Following the launch of the awareness programme, later in 2015, CRB was also reported from the Shortland Islands in the Western Province. Other islands were surveyed from 2015 to 2020. If CRB presence was confirmed, beetles were collected and analysed for haplotype and presence of the classical biological control agent, Oryctes rhinoceros nudivirus (OrNV). A distribution map and timeline of invasion were developed. The initial populations belonged to two distinct haplotypes: CRB-G (clade IA) in Honiara and CRB-S (clade II) in Shortland Islands. Despite control measures, by 2020 CRB-G had spread to islands in eight provinces and CRB-S had spread to islands in seven provinces. CRB-S and CRB-G co-occur in Guadalcanal and Malaita provinces. In 2019, OrNV was detected from field collected CRB from Guadalcanal and has since spread to Malaita Island. In both cases the virus was detected where CRB-G and CRB-S co-occur. Other outbreak areas in Solomon Islands remain OrNV-free. The two haplotypes appear to have spread following patterns of air and sea movement between the point of origin (CRB-G from Honiara and CRB-S from the Shortland Islands) to other islands/provinces.

Mpox Update: Clinical Presentation, Vaccination Guidance, and Management

Following the eradication of smallpox, intermittent small outbreaks of mpox (monkeypox) have occurred with increasing frequency, primarily in endemic regions of Africa. With the rapid spread of mpox around the globe in 2022, we are approaching a second zoonotic pandemic of the 21st century. Given the predominance of cutaneous involvement in mpox, dermatologists should be prepared to recognize the clinical features and manage this increasingly prevalent disease. This article reviews a brief history of the mpox virus, clinical presentation, complications, approach to diagnosis, methods of transmission, infection control recommendations, indications for vaccination, and therapeutic options to inform dermatologists on the frontline of the mpox epidemic.

Optimal Contact Tracing and Social Distancing Policies to Suppress A New Infectious Disease

Abstract This paper studies the suppression of an infectious disease in the canonical susceptible-infectious-recovered model. It derives three results. First, if technically feasible, the optimal response to a sufficiently small outbreak is halting transmissions instead of building up immunity through infections. Second, the crucial trade-off is not between health and economic costs, but between the intensity and duration of control measures. A simple formula of observables characterises the optimum. Third, the total cost depends critically on the efficiency of contact tracing, since it allows relaxing costly social distancing without increasing transmissions. A calibration to the COVID-19 pandemic illustrates the theoretical findings.

Largest dengue outbreak (2022) in Nepal

Dengue virus infection, transmitted by Aedes aegypti (also by Ae. albopictus) mosquito, is an increasing health problem. The number of dengue cases has increased over eight-fold over the last two decades, from 505,430 cases in 2000, to over 2.4 milli on in 2010, and 5.2 million in 2019 with deaths accounting in thousands. Currently, 3.9 billion people in 129 countries mainly in Asian countries are at the risk of dengue infection. Most of the new cases are reported from Brazil, Vietnam, Indonesia, the Philippines, Sri Lanka and others. First case of dengue was reported from Nepal in 2004 and in 2006 a small outbreak was reported with 32 cases throughout the country. In Nepal, dengue epidemic occurred in 2010, 2013, 2016, 2017, and 2019; of them 2019 epidemic was largest one with reported 17,992 cases. This year (2022) largest outbreak occurred with a total of 54,784 cases recorded from all 77 districts in 7 provinces. Of the 7 provinces Bagmati Province was hardest hit (77.4%) followed by Lumbini Province (9.2%), Province 1 (4.2%), Gandaki Province (3.6%), Sudur Pashchim Province (2.5%), Madhesh Province (1.8%) and Karnali Province (1.2%). Most of the patients were aged 15-59 years and slightly more than half were males. Of the four serotypes existed in Nepal, DENV-1 DENV-2 and DENV-3 were common this year’s outbreak (DENV-1 was predominant: 57.1%). This demands a precise mapping of dengue through integrated disease surveillance and evaluation of the dynamics of population-level immunity on evidence-based policy-making in days to come.

Prevalence of HEV infection in acute non-ABC hepatitis and prognostic role of extrahepatic manifestations.

HEV-3 and HEV-4 are emerging cause of zoonotic acute hepatitis in high-income countries. In Europe the disease is underdiagnosed but hyperendemic areas have been identified. We describe a population with acute non-ABC (n-ABC) hepatitis in Abruzzo, the Italian region with the highest seroprevalence reported. The study was included in the surveillance of acute hepatitis E by the Italian Institute of Public Health started in 2004 and implemented in 2015. Patients with n-ABC hepatitis during 2004-2018 in all Abruzzo Infectious Disease Departments were tested for HEV-IgM (Wantai®) and HEV-RNA (ORF3). Positive samples were sequenced (Beckman Coulter®) and phylogenetic tree (MEGA 6.06 software) obtained. Clinical data were retrospectively collected and an alimentary risk factors-questionnaire was administered. Categorical and quantitative variables were compared (Chi square test or Fisher test and Wilcoxon test). 97 hospitalized patients were tested, most cases (91.7%) after 2015. Overall, HEV-IgM resulted positive in 36% and HEV-RNA detectable in 33.3%. All 24 sequences obtained were HEV-3, with two small groups of closely related strands. L'Aquila was the Province with higher positivity rate (44%). Retrospective clinical data were acquired in 86.5% of patients, no one having liver failure. Higher ALT-levels (1282.34 vs 893.25, p=0.0139) and extrahepatic symptoms (OR 16.69, p=0.0018) were strongly associated with HEV-IgM presence. Two small outbreaks are described. More than one third of n-ABC hepatitis in all Abruzzo are HEV-related. Extrahepatic symptoms correlate with HEV aetiology. Implementing surveillance is mandatory to really understand the extent of the disease.

Molecular Tracking of the Origin of Vesicular Stomatitis Outbreaks in 2004 and 2018, Ecuador

The Vesicular Stomatitis Virus (VSV) is an arbovirus causing vesicular stomatitis (VS) in livestock. There are two serotypes recognized: New Jersey (VSNJV) and Indiana (VSIV). The virus can be transmitted directly by contact or by vectors. In 2018, Ecuador experienced an outbreak of Vesicular Stomatitis (VS) in cattle, caused by VSNJV and VSVIV, with 399 cases reported distributed over 18 provinces. We determined the phylogenetic relationships among 67 strains. For the construction of phylogenetic trees, the viral phosphoprotein gene was sequenced, and trees were constructed based on the Maximum Likelihood method using 2004 outbreak strains from Ecuador (GenBank) and the 2018 sequences (this article). We built a haplotype network for VSNJV to trace the origin of the 2004 and 2018 epizootics through topology and mutation connections. These analyses suggest two different origins, one related to the 2004 outbreak and the other from a transmission source in 2018. Our analysis also suggests different transmission patterns; several small and independent outbreaks, most probably transmitted by vectors in the Amazon, and another outbreak caused by the movement of livestock in the Andean and Coastal regions. We recommend further research into vectors and vertebrate reservoirs in Ecuador to clarify the mechanisms of the reemergence of the virus.

Infection transmission via mobile phones in a mass gathering setting: Public knowledge, attitudes and practices in Makkah city, Saudi Arabia

BackgroundMobile phones have become part of everyday life with a potential risk for microbial transmission. Makkah is a mass gathering city that may act as hotspots of disease transmission. The contact between public and both visitors and pilgrims to Makkah can't be overlooked, and any small outbreak within the public can be transmitted rapidly to them. AimWe aimed to assess knowledge, attitudes, and practices (KAP) of general population towards infection transmission via mobile phones in Makkah and different characteristics relevant to KAP scores. MethodsA cross-sectional web-based survey was conducted on general population in Makkah city using a snowballing sampling method. Participants answered questions about their KAP towards infection transmission via mobile phone. The overall KAP scores were graded as good, fair, and poor and explored against different population characteristics using suitable statistical methods. ResultsThe study included 385 participants aged 15–64 years. About 88.8% owned personal mobile phone, 3.9% encountering a patient with infections transmitted via mobile phones, and 60.5% know nothing about potential role of mobile phones in infection transmission. Only 16.6% had good knowledge, 64.1% with positive attitudes, and 55.3% reported poor practices. The mean knowledge score was significantly higher among young adults (p = 0.002) and those with higher education (p = 0.005). Their mean attitude and practice scores were significantly higher among older adults (p < 0.001 and p = 0.015), female (p = 0.001 and p = 0.022), and those with higher education (p = 0.036 and p = 0.041) respectively. ConclusionThe overall public knowledge and practices towards the role of mobile phones in infection transmission in Makkah was below average though they have positive attitudes. Raising public awareness is important to decrease the possibility of cross-contamination via mobile phones and to develop adequate preventive strategies in a mass gathering setting like Makkah city.

Malaria in Children: Updates on Management and Prevention.

Malaria in Children: Updates on Management and Prevention.

Power Law for Estimating Underdetection of Foodborne Disease Outbreaks, United States.

We fit a power law distribution to US foodborne disease outbreaks to assess underdetection and underreporting. We predicted that 788 fewer than expected small outbreaks were identified annually during 1998-2017 and 365 fewer during 2018-2019, after whole-genome sequencing was implemented. Power law can help assess effectiveness of public health interventions.