Trends in Disease Severity and Health Care Utilization During the Early Omicron Variant Period Compared with Previous SARS-CoV-2 High Transmission Periods - United States, December 2020-January 2022.

The B.1.1.529 (Omicron) variant of SARS-CoV-2, the virus that causes COVID-19, was first clinically identified in the United States on December 1, 2021, and spread rapidly. By late December, it became the predominant strain, and by January 15, 2022, it represented 99.5% of sequenced specimens in the United States* (1). The Omicron variant has been shown to be more transmissible and less virulent than previously circulating variants (2,3). To better understand the severity of disease and health care utilization associated with the emergence of the Omicron variant in the United States, CDC examined data from three surveillance systems and a large health care database to assess multiple indicators across three high-COVID-19 transmission periods: December 1, 2020-February 28, 2021 (winter 2020-21); July 15-October 31, 2021 (SARS-CoV-2 B.1.617.2 [Delta] predominance); and December 19, 2021-January 15, 2022 (Omicron predominance). The highest daily 7-day moving average to date of cases (798,976 daily cases during January 9-15, 2022), emergency department (ED) visits (48,238), and admissions (21,586) were reported during the Omicron period, however, the highest daily 7-day moving average of deaths (1,854) was lower than during previous periods. During the Omicron period, a maximum of 20.6% of staffed inpatient beds were in use for COVID-19 patients, 3.4 and 7.2 percentage points higher than during the winter 2020-21 and Delta periods, respectively. However, intensive care unit (ICU) bed use did not increase to the same degree: 30.4% of staffed ICU beds were in use for COVID-19 patients during the Omicron period, 0.5 percentage points lower than during the winter 2020-21 period and 1.2 percentage points higher than during the Delta period. The ratio of peak ED visits to cases (event-to-case ratios) (87 per 1,000 cases), hospital admissions (27 per 1,000 cases), and deaths (nine per 1,000 cases [lagged by 3 weeks]) during the Omicron period were lower than those observed during the winter 2020-21 (92, 68, and 16 respectively) and Delta (167, 78, and 13, respectively) periods. Further, among hospitalized COVID-19 patients from 199 U.S. hospitals, the mean length of stay and percentages who were admitted to an ICU, received invasive mechanical ventilation (IMV), and died while in the hospital were lower during the Omicron period than during previous periods. COVID-19 disease severity appears to be lower during the Omicron period than during previous periods of high transmission, likely related to higher vaccination coverage,† which reduces disease severity (4), lower virulence of the Omicron variant (3,5,6), and infection-acquired immunity (3,7). Although disease severity appears lower with the Omicron variant, the high volume of ED visits and hospitalizations can strain local health care systems in the United States, and the average daily number of deaths remains substantial.§ This underscores the importance of national emergency preparedness, specifically, hospital surge capacity and the ability to adequately staff local health care systems. In addition, being up to date on vaccination and following other recommended prevention strategies are critical to preventing infections, severe illness, or death from COVID-19.

El Niño and the shifting geography of cholera in Africa.

The El Niño Southern Oscillation (ENSO) and other climate patterns can have profound impacts on the occurrence of infectious diseases ranging from dengue to cholera. In Africa, El Niño conditions are associated with increased rainfall in East Africa and decreased rainfall in southern Africa, West Africa, and parts of the Sahel. Because of the key role of water supplies in cholera transmission, a relationship between El Niño events and cholera incidence is highly plausible, and previous research has shown a link between ENSO patterns and cholera in Bangladesh. However, there is little systematic evidence for this link in Africa. Using high-resolution mapping techniques, we find that the annual geographic distribution of cholera in Africa from 2000 to 2014 changes dramatically, with the burden shifting to continental East Africa-and away from Madagascar and portions of southern, Central, and West Africa-where almost 50,000 additional cases occur during El Niño years. Cholera incidence during El Niño years was higher in regions of East Africa with increased rainfall, but incidence was also higher in some areas with decreased rainfall, suggesting a complex relationship between rainfall and cholera incidence. Here, we show clear evidence for a shift in the distribution of cholera incidence throughout Africa in El Niño years, likely mediated by El Niño's impact on local climatic factors. Knowledge of this relationship between cholera and climate patterns coupled with ENSO forecasting could be used to notify countries in Africa when they are likely to see a major shift in their cholera risk.

Cholera Epidemic - Lusaka, Zambia, October 2017-May 2018.

On October 6, 2017, an outbreak of cholera was declared in Zambia after laboratory confirmation of Vibrio cholerae O1, biotype El Tor, serotype Ogawa, from stool specimens from two patients with acute watery diarrhea. The two patients had gone to a clinic in Lusaka, the capital city, on October 4. Cholera cases increased rapidly, from several hundred cases in early December 2017 to approximately 2,000 by early January 2018 (Figure). In collaboration with partners, the Zambia Ministry of Health (MoH) launched a multifaceted public health response that included increased chlorination of the Lusaka municipal water supply, provision of emergency water supplies, water quality monitoring and testing, enhanced surveillance, epidemiologic investigations, a cholera vaccination campaign, aggressive case management and health care worker training, and laboratory testing of clinical samples. In late December 2017, a number of water-related preventive actions were initiated, including increasing chlorine levels throughout the city's water distribution system and placing emergency tanks of chlorinated water in the most affected neighborhoods; cholera cases declined sharply in January 2018. During January 10-February 14, 2018, approximately 2 million doses of oral cholera vaccine were administered to Lusaka residents aged ≥1 year. However, in mid-March, heavy flooding and widespread water shortages occurred, leading to a resurgence of cholera. As of May 12, 2018, the outbreak had affected seven of the 10 provinces in Zambia, with 5,905 suspected cases and a case fatality rate (CFR) of 1.9%. Among the suspected cases, 5,414 (91.7%), including 98 deaths (CFR = 1.8%), occurred in Lusaka residents.

Cluster of Ebola Virus Disease Linked to a Single Funeral - Moyamba District, Sierra Leone, 2014.

As of February 17, 2016, a total of 14,122 cases (62% confirmed) of Ebola Virus Disease (Ebola) and 3,955 Ebola-related deaths had been reported in Sierra Leone since the epidemic in West Africa began in 2014. A key focus of the Ebola response in Sierra Leone was the promotion and implementation of safe, dignified burials to prevent Ebola transmission by limiting contact with potentially infectious corpses. Traditional funeral practices pose a substantial risk for Ebola transmission through contact with infected bodies, body fluids, contaminated clothing, and other personal items at a time when viral load is high; however, the role of funeral practices in the Sierra Leone epidemic and ongoing Ebola transmission has not been fully characterized. In September 2014, a sudden increase in the number of reported Ebola cases occurred in Moyamba, a rural and previously low-incidence district with a population of approximately 260,000. The Sierra Leone Ministry of Health and Sanitation and CDC investigated and implemented public health interventions to control this cluster of Ebola cases, including community engagement, active surveillance, and close follow-up of contacts. A retrospective analysis of cases that occurred during July 11-October 31, 2014, revealed that 28 persons with confirmed Ebola had attended the funeral of a prominent pharmacist during September 5-7, 2014. Among the 28 attendees with Ebola, 21 (75%) reported touching the man's corpse, and 16 (57%) reported having direct contact with the pharmacist before he died. Immediate, safe, dignified burials by trained teams with appropriate protective equipment are critical to interrupt transmission and control Ebola during times of active community transmission; these measures remain important during the current response phase.

Mapping of cholera hotspots in Kenya using epidemiologic and water, sanitation, and hygiene (WASH) indicators as part of Kenya's new 2022-2030 cholera elimination plan.

Cholera is an issue of major public health importance. It was first reported in Kenya in 1971, with the country experiencing outbreaks through the years, most recently in 2021. Factors associated with the outbreaks in Kenya include open defecation, population growth with inadequate expansion of safe drinking water and sanitation infrastructure, population movement from neighboring countries, crowded settings such as refugee camps coupled with massive displacement of persons, mass gathering events, and changes in rainfall patterns. The Ministry of Health, together with other ministries and partners, revised the national cholera control plan to a multisectoral cholera elimination plan that is aligned with the Global Roadmap for Ending Cholera. One of the key features in the revised plan is the identification of hotspots. The hotspot identification exercise followed guidance and tools provided by the Global Task Force on Cholera Control (GTFCC). Two epidemiological indicators were used to identify the sub-counties with the highest cholera burden: incidence per population and persistence. Additionally, two indicators were used to identify sub-counties with poor WASH coverage due to low proportions of households accessing improved water sources and improved sanitation facilities. The country reported over 25,000 cholera cases between 2015 and 2019. Of 290 sub-counties, 25 (8.6%) sub-counties were identified as a high epidemiological priority; 78 (26.9%) sub-counties were identified as high WASH priority; and 30 (10.3%) sub-counties were considered high priority based on a combination of epidemiological and WASH indicators. About 10% of the Kenyan population (4.89 million) is living in these 30-combination high-priority sub-counties. The novel method used to identify cholera hotspots in Kenya provides useful information to better target interventions in smaller geographical areas given resource constraints. Kenya plans to deploy oral cholera vaccines in addition to WASH interventions to the populations living in cholera hotspots as it targets cholera elimination by 2030.

Causes of outbreaks associated with drinking water in the United States from 1971 to 2006.

Since 1971, the CDC, EPA, and Council of State and Territorial Epidemiologists (CSTE) have maintained the collaborative national Waterborne Disease and Outbreak Surveillance System (WBDOSS) to document waterborne disease outbreaks (WBDOs) reported by local, state, and territorial health departments. WBDOs were recently reclassified to better characterize water system deficiencies and risk factors; data were analyzed for trends in outbreak occurrence, etiologies, and deficiencies during 1971 to 2006. A total of 833 WBDOs, 577,991 cases of illness, and 106 deaths were reported during 1971 to 2006. Trends of public health significance include (i) a decrease in the number of reported outbreaks over time and in the annual proportion of outbreaks reported in public water systems, (ii) an increase in the annual proportion of outbreaks reported in individual water systems and in the proportion of outbreaks associated with premise plumbing deficiencies in public water systems, (iii) no change in the annual proportion of outbreaks associated with distribution system deficiencies or the use of untreated and improperly treated groundwater in public water systems, and (iv) the increasing importance of Legionella since its inclusion in WBDOSS in 2001. Data from WBDOSS have helped inform public health and regulatory responses. Additional resources for waterborne disease surveillance and outbreak detection are essential to improve our ability to monitor, detect, and prevent waterborne disease in the United States.

Outbreak of cryptosporidiosis associated with a man-made chlorinated lake--Tarrant County, Texas, 2008.

In July 2008, clusters of laboratory-confirmed cryptosporidiosis cases and reports of gastrointestinal illness in persons who visited a lake were reported to Tarrant County Public Health. In response, epidemiologic, laboratory, and environmental health investigations were initiated. A matched case-control study determined that swallowing the lake water was associated with illness (adjusted odds ratio = 16.3; 95% confidence interval: 2.5-infinity). The environmental health investigation narrowed down the potential sources of contamination. Laboratory testing detected Cryptosporidium hominis in case-patient stool specimens and Cryptosporidium species in lake water. It was only through the joint effort that epidemiologic, laboratory, and environmental health investigators could determine that >1 human diarrheal fecal incidents in the lake likely led to contamination of the water. This same collaborative effort will be needed to develop and maintain an effective national Model Aquatic Health Code.

Cholera prevention training materials for community health workers, Haiti, 2010­2011.

Stopping the spread of the cholera epidemic in Haiti required engaging community health workers (CHWs) in prevention and treatment activities. The Centers for Disease Control and Prevention collaborated with the Haitian Ministry of Public Health and Population to develop CHW educational materials, train >1,100 CHWs, and evaluate training efforts.

Risk Factors for Epidemic Cholera in Lusaka, Zambia-2017.

On October 6, 2017, the Zambia Ministry of Health declared a cholera outbreak in Lusaka. By December, 1,462 cases and 38 deaths had occurred (case fatality rate, 2.6%). We conducted a case-control study to identify risk factors and inform interventions. A case was any person with acute watery diarrhea (≥ 3 loose stools in 24 hours) admitted to a cholera treatment center in Lusaka from December 16 to 21, 2017. Controls were neighbors without diarrhea during the same time period. Up to two controls were matched to each case by age-group (1-4, 5-17, and ≥ 18 years) and neighborhood. Surveyors interviewed cases and controls, tested free chlorine residual (FCR) in stored water, and observed the presence of soap in the home. Conditional logistic regression was used to generate matched odds ratios (mORs) based on subdistricts and age-groups with 95% CIs. We enrolled 82 cases and 132 controls. Stored water in 71% of case homes had an FCR > 0.2 mg/L. In multivariable analyses, those who drank borehole water (mOR = 2.4, CI: 1.1-5.6), had close contact with a cholera case (mOR = 6.2, CI: 2.5-15), and were male (mOR = 2.5, CI: 1.4-5.0) had higher odds of being a cholera case than their matched controls. Based on these findings, we recommended health education about household water chlorination and hygiene in the home. Emergency responses included providing chlorinated water through emergency tanks and maintaining adequate FCR levels through close monitoring of water sources.

Risk and Protective Factors for Cholera Deaths during an Urban Outbreak-Lusaka, Zambia, 2017-2018.

The Republic of Zambia declared a cholera outbreak in Lusaka, the capital, on October 6, 2017. By mid-December, 20 of 661 reported cases had died (case fatality rate 3%), prompting the CDC and the Zambian Ministry of Health through the Zambia National Public Health Institute to investigate risk factors for cholera mortality. We conducted a study of cases (cholera deaths from October 2017 to January 2018) matched by age-group and onset date to controls (persons admitted to a cholera treatment center [CTC] and discharged alive). A questionnaire was administered to each survivor (or relative) and to a family member of each decedent. We used univariable exact conditional logistic regression to calculate matched odds ratios (mORs) and 95% CIs. In the analysis, 38 decedents and 76 survivors were included. Median ages for decedents and survivors were 38 (range: 0.5-95) and 25 (range: 1-82) years, respectively. Patients aged > 55 years and those who did not complete primary school had higher odds of being decedents (matched odds ratio [mOR] 6.3, 95% CI: 1.2-63.0, P = 0.03; mOR 8.6, 95% CI: 1.8-81.7, P < 0.01, respectively). Patients who received immediate oral rehydration solution (ORS) at the CTC had lower odds of dying than those who did not receive immediate ORS (mOR 0.1, 95% CI: 0.0-0.6, P = 0.02). Cholera prevention and outbreak response should include efforts focused on ensuring access to timely, appropriate care for older adults and less educated populations at home and in health facilities.

Staphylococcus aureus community-acquired pneumonia during the 2006 to 2007 influenza season.

STUDY OBJECTIVE: Staphylococcus aureus is a cause of community-acquired pneumonia that can follow influenza infection. In response to a number of cases reported to public health authorities in early 2007, additional case reports were solicited nationwide to better define S. aureus community-acquired pneumonia during the 2006 to 2007 influenza season. METHODS: Cases were defined as primary community-acquired pneumonia caused by S. aureus occurring between November 1, 2006, and April 30, 2007. Case finding was conducted through an Emerging Infections Network survey and through contacts with state and local health departments. RESULTS: Overall, 51 cases were reported from 19 states; 37 (79%) of 47 with known susceptibilities involved infection with methicillin-resistant S. aureus (MRSA). The median age of case patients was 16 years, and 44% had no known pertinent medical history. Twenty-two (47%) of 47 case patients with information about other illnesses were diagnosed with a concurrent or antecedent viral infection during their illness, and 11 of 33 (33%) who were tested had laboratory-confirmed influenza. Of the 37 patients with MRSA infection, 16 (43%) were empirically treated with antimicrobial agents recommended for MRSA community-acquired pneumonia. Twenty-four (51%) of 47 patients for whom final disposition was known died a median of 4 days after symptom onset. CONCLUSION: S. aureus continues to cause community-acquired pneumonia, with most reported cases caused by MRSA and many occurring with or after influenza. In this series, patients were often otherwise healthy young people and mortality rates were high. Further prospective investigation is warranted to clarify infection incidence, risk factors, and preventive measures.

Increase in Reported Cholera Cases in Haiti Following Hurricane Matthew: An Interrupted Time Series Model.

Matthew, a category 4 hurricane, struck Haiti on October 4, 2016, causing widespread flooding and damage to buildings and crops, and resulted in many deaths. The damage caused by Matthew raised concerns of increased cholera transmission particularly in Sud and Grand'Anse departments, regions which were hit most heavily by the storm. To evaluate the change in reported cholera cases following Hurricane Matthew on reported cholera cases, we used interrupted time series regression models of daily reported cholera cases, controlling for the impact of both rainfall, following a 4-week lag, and seasonality, from 2013 through 2016. Our results indicate a significant increase in reported cholera cases after Matthew, suggesting that the storm resulted in an immediate surge in suspect cases, and a decline in reported cholera cases in the 46-day post-storm period, after controlling for rainfall and seasonality. Regression models stratified by the department indicate that the impact of the hurricane was regional, with larger surges in the two most highly storm-affected departments: Sud and Grand'Anse. These models were able to provide input to the Ministry of Health in Haiti on the national and regional impact of Hurricane Matthew and, with further development, could provide the flexibility of use in other emergency situations. This article highlights the need for continued cholera prevention and control efforts, particularly in the wake of natural disasters such as hurricanes, and the continued need for intensive cholera surveillance nationally.

Epidemic dengue and dengue hemorrhagic fever at the Texas-Mexico border: results of a household-based seroepidemiologic survey, December 2005.

A dengue-2 epidemic causing dengue hemorrhagic fever (DHF) occurred in the contiguous border cities of Matamoros, Tamaulipas (Mexico), and Brownsville, TX, in 2005. In December, we conducted a household-based epidemiologic survey to determine the incidence and seroprevalence of dengue infection among Matamoros and Brownsville residents and to identify risk factors associated with infection. Antibodies to dengue were measured in 273 individuals. The estimated incidence of recent dengue infection was 32% and 4% among Matamoros and Brownsville participants, respectively. The estimated prevalence of past dengue infection was 77% and 39% among Matamoros and Brownsville participants, respectively. The Breteau index was 28 in Matamoros and 16 in Brownsville, reflecting an abundant winter population of Aedes mosquitoes. Discarded waste tires and buckets were the two largest categories of infested containers found in both cities. Our results underscore the risk for epidemic dengue and DHF in the Texas-Mexico border region.

Assessing the roles of temperature, precipitation, and ENSO in dengue re-emergence on the Texas-Mexico border region.

OBJECTIVE: The goal of this study was to assess linkages between microclimate and longer-term ENSO-related weather forcing on the week-to-week changes in dengue prevalence in Matamoros, Tamaulipas, Mexico, over a recent decade of dengue observations. MATERIAL AND METHODS: An auto-regressive model to evaluate the role of climatic factors (sea-surface temperature) and weather (maximum temperature, minimum temperature, precipitation) on dengue incidence over the period 1995-2005, was developed by conducting time-series analysis. RESULTS: Dengue incidence increased by 2.6% (95% CI: 0.2-5.1) one week after every 1 degree Celsius increase in weekly maximum temperature and increased 1.9% (95% CI: -0.1-3.9) two weeks after every 1 cm increase in weekly precipitation. Every 1 masculineC increase in sea surface temperatures (El Niño region 3.4 ) was followed by a 19.4% (95% CI: -4.7-43.5) increase in dengue incidence (18 weeks later). CONCLUSIONS: Climate and weather factors play a small but significant role in dengue transmission in Matamoros, Mexico. This study may provide baseline information for identifying potential longer-term effects of global climate change on dengue expected in the coming decades. To our knowledge, this is the first study to investigate the potential associations between climate and weather events and dengue incidence in this geographical area.

Dengue fever seroprevalence and risk factors, Texas-Mexico border, 2004.

Reported autochthonous dengue fever transmission in the United States has been limited to 5 south Texas border counties since 1980. We conducted a cross-sectional serosurvey in Brownsville, Texas, and Matamoros, Tamaulipas, Mexico (n = 600), in 2004 to assess dengue seroprevalence. Recent dengue infection was detected in 2% (95% confidence interval [CI] 0.5%-3.5%) and 7.3% (95% CI 4.3%-10.3%) of residents in Brownsville and Matamoros, respectively. Past infection was detected in 40% (95% CI 34%-45%) of Brownsville residents and 78% (95% CI 74%-83%) of Matamoros residents. For recent infection, only weekly family income

Rapid assessment procedures in environmental sanitation research: a case study from the northern border of Mexico.

BACKGROUND: There is a need to enhance the quality and sustainability of environmental health programs in Mexico. What socio-cultural factors influenced the adoption or rejection of Clean Water in Homes programs in this population? We applied rapid appraisal procedures (RAP) to evaluate these community-based programs. METHOD: Qualitative study conducted in communities along Mexico's northern border. We conducted informal dialogues, semi-structured interviews, field notes and observations. Home visits used a checklist to observe: sources of water, handwashing, as well as human waste and garbage disposal patterns. Data analysis was conducted using ATLAS.ti, which facilitated comparison and illustration of discrepancies, the elaboration of emerging issues and relationships between them. RESULTS: Community members perceived that the Clean Water program was a top-down intervention. Water is perceived as a political issue and a matter of corruption. Inequity also limits solidarity activities involved in environmental sanitation. Migration to the United States of America (US) contributes to community fragmentation, which in turn dilutes communal efforts to improve water and sanitation infrastructure. While targeting women as program "recipients", the Clean Water program did not take gendered spheres of decision-making into account. Community members and authorities discussed the main results in "assemblies", particularly addressing the needs of excluded groups. CONCLUSION: The oversight of not exploring community members' needs and priorities prior to program implementation resulted in interventions that did not address the structural (economic, infrastructure) and socio-cultural barriers faced by community members to undertake the health-promoting behaviour change, and provoked resentment.

Contributing factors to disease outbreaks associated with untreated groundwater.

Disease outbreaks associated with drinking water drawn from untreated groundwater sources represent a substantial proportion (30.3%) of the 818 drinking water outbreaks reported to CDC's Waterborne Disease and Outbreak Surveillance System (WBDOSS) during 1971 to 2008. The objectives of this study were to identify underlying contributing factors, suggest improvements for data collection during outbreaks, and inform outbreak prevention efforts. Two researchers independently reviewed all qualifying outbreak reports (1971 to 2008), assigned contributing factors and abstracted additional information (e.g., cases, etiology, and water system attributes). The 248 outbreaks resulted in at least 23,478 cases of illness, 390 hospitalizations, and 13 deaths. The majority of outbreaks had an unidentified etiology (n = 135, 54.4%). When identified, the primary etiologies were hepatitis A virus (n = 21, 8.5%), Shigella spp. (n = 20, 8.1%), and Giardia intestinalis (n = 14, 5.7%). Among the 172 (69.4%) outbreaks with contributing factor data available, the leading contamination sources included human sewage (n = 57, 33.1%), animal contamination (n = 16, 9.3%), and contamination entering via the distribution system (n = 12, 7.0%). Groundwater contamination was most often facilitated by improper design, maintenance or location of the water source or nearby waste water disposal system (i.e., septic tank; n = 116, 67.4%). Other contributing factors included rapid pathogen transport through hydrogeologic formations (e.g., karst limestone; n = 45, 26.2%) and preceding heavy rainfall or flooding (n = 36, 20.9%). This analysis underscores the importance of identifying untreated groundwater system vulnerabilities through frequent inspection and routine maintenance, as recommended by protective regulations such as Environmental Protection Agency's (EPA's) Groundwater Rule, and the need for special consideration of the local hydrogeology.

Cholera epidemic associated with consumption of unsafe drinking water and street-vended water--Eastern Freetown, Sierra Leone, 2012.

During 2012, Sierra Leone experienced a cholera epidemic with 22,815 reported cases and 296 deaths. We conducted a matched case-control study to assess risk factors, enrolling 49 cases and 98 controls. Stool specimens were analyzed by culture, polymerase chain reaction (PCR), and pulsed-field gel electrophoresis (PFGE). Conditional logistic regression found that consuming unsafe water (matched odds ratio [mOR]: 3.4; 95% confidence interval [CI]: 1.1, 11.0), street-vended water (mOR: 9.4; 95% CI: 2.0, 43.7), and crab (mOR: 3.3; 95% CI: 1.03, 10.6) were significant risk factors for cholera infection. Of 30 stool specimens, 13 (43%) showed PCR evidence of toxigenic Vibrio cholerae O1. Six specimens yielded isolates of V. cholerae O1, El Tor; PFGE identified a pattern previously observed in seven countries. We recommended ensuring the quality of improved water sources, promoting household chlorination, and educating street vendors on water handling practices.