Reducing travel-related SARS-CoV-2 transmission with layered mitigation measures: symptom monitoring, quarantine, and testing.

BACKGROUND: Balancing the control of SARS-CoV-2 transmission with the resumption of travel is a global priority. Current recommendations include mitigation measures before, during, and after travel. Pre- and post-travel strategies including symptom monitoring, antigen or nucleic acid amplification testing, and quarantine can be combined in multiple ways considering different trade-offs in feasibility, adherence, effectiveness, cost, and adverse consequences. METHODS: We used a mathematical model to analyze the expected effectiveness of symptom monitoring, testing, and quarantine under different estimates of the infectious period, test-positivity relative to time of infection, and test sensitivity to reduce the risk of transmission from infected travelers during and after travel. RESULTS: If infection occurs 0-7 days prior to travel, immediate isolation following symptom onset prior to or during travel reduces risk of transmission while traveling by 30-35%. Pre-departure testing can further reduce risk, with testing closer to the time of travel being optimal even if test sensitivity is lower than an earlier test. For example, testing on the day of departure can reduce risk while traveling by 44-72%. For transmission risk after travel with infection time up to 7 days prior to arrival at the destination, isolation based on symptom monitoring reduced introduction risk at the destination by 42-56%. A 14-day quarantine after arrival, without symptom monitoring or testing, can reduce post-travel risk by 96-100% on its own. However, a shorter quarantine of 7 days combined with symptom monitoring and a test on day 5-6 after arrival is also effective (97--100%) at reducing introduction risk and is less burdensome, which may improve adherence. CONCLUSIONS: Quarantine is an effective measure to reduce SARS-CoV-2 transmission risk from travelers and can be enhanced by the addition of symptom monitoring and testing. Optimal test timing depends on the effectiveness of quarantine: with low adherence or no quarantine, optimal test timing is close to the time of arrival; with effective quarantine, testing a few days later optimizes sensitivity to detect those infected immediately before or while traveling. These measures can complement recommendations such as social distancing, using masks, and hand hygiene, to further reduce risk during and after travel.

Eczema vaccinatum resulting from the transmission of vaccinia virus from a smallpox vaccinee: an investigation of potential fomites in the home environment.

On March 3, 2007, a 2-year-old boy was hospitalized with eczema vaccinatum. His two siblings, one with eczema, were subsequently removed from the home. Swabs of household items obtained on March 13th were analyzed for orthopoxvirus DNA signatures with real-time PCR. Virus culture was attempted on positive specimens. Eight of 25 household samples were positive by PCR for orthopoxvirus; of these, three yielded viable vaccinia virus in culture. Both siblings were found to have serologic evidence of orthopoxvirus exposure. These findings have implications for smallpox preparedness, especially in situations where some household members are not candidates for vaccination.

Molecular epidemiology of Neisseria meningitidis isolates from an outbreak of meningococcal disease among men who have sex with men, Chicago, Illinois, 2003.

We characterized five Neisseria meningitidis serogroup C isolates from a Chicago outbreak of meningococcal disease that occurred in 2003 among a community of men who have sex with men. Isolates from this outbreak were identical to each other but distinct from the clone that caused a similar outbreak in Canada in 2001.

Outbreak of food-borne illness associated with plant material containing raphides.

BACKGROUND: Many botanicals, particularly ornamental house-plants, contain crystals of calcium oxalate called raphides. Raphides have known toxic effects when chewed, including painful edema, vesicle formation, and dysphagia. We report a food-borne illness outbreak associated with ingestion of raphides. METHODS: On February 24, 2003, the Chicago Department of Public Health was notified of multiple cases of oral burning and facial edema associated with lunch in an office cafeteria on February 21. The investigation included a case-control study, interviews with kitchen staff, an environmental inspection, and laboratory analysis of leftover foods. RESULTS: Ten cases were identified, including one admitted to the Intensive Care Unit for potential airway obstruction secondary to severe edema, and another seen by Emergency Department staff for oral edema and pain. Ten of 10 case-patients reported oral stinging and burning, and 8 of 10 reported dysphagia. Four of 10 case-patients continued to have symptoms 2 weeks later. Food from the cafeteria's international buffet was consumed by 10 of 10 case-patients and by 1 of 22 control subjects (odds ratio=undefined); each of the 10 case-patients reported consumption of a Chinese vegetable entrée from the international buffet and had no other foods in common. Plant material from the Chinese vegetable entrée contained raphides. CONCLUSION: This outbreak was associated with consumption of raphides resembling those from common botanicals. Clinicians and public health practitioners should be aware of raphide-containing plants as a potential cause of food-borne illness.

Intensive investigation of bacterial foodborne disease outbreaks: proposed guidelines and tools for the collection of dose-response data by local health departments.

Local health departments that investigate foodborne disease outbreaks do not have adequate guidelines for collecting data that could be used to estimate dose-response relationships, a key component of hazard characterization in quantitative microbial risk assessment. To meet this need, criteria and a questionnaire template for the collection of appropriate dose-response data in the context of outbreaks were developed and applied in the investigation of a point-source outbreak linked to Salmonella serotype Enteritidis in a salmon entrée in February 2000. In this outbreak, the attack rate and risk of hospitalization increased with the amount of salmon entrée consumed, and detailed data were obtained on illness severity measures and host susceptibility factors. Local health departments might consider broadening investigations to include the collection of additional data when investigating outbreaks that have met a specific set of conditions. These data could provide information needed by federal regulatory agencies and other organizations for quantitative microbial risk assessment. Intensive investigations of outbreaks could prevent future illnesses by providing information needed to develop approaches to minimizing risk.

Underimmunization in Chicago children who dropped out of WIC.

BACKGROUND: The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) serves a large proportion of Chicago infants, but some discontinue participation before age 1 year. To determine if children who remained active at WIC immunization-linked sites after their first birthday were more likely to be immunized by ages 19 and 25 months than those who dropped out, a retrospective cohort study was conducted. METHODS: Four Chicago WIC sites that used monthly voucher pick-up were chosen. Children born from July 1, 1997 to September 30, 1997 who attended these sites were eligible (N=1142). The cohort was divided into two groups: (1) active group (46%), who had a WIC visit on or after their first birthday; and (2) inactive group (54%), who had their last WIC visit before their first birthday. Children were enrolled through home visits. RESULTS: The records for 200 children were analyzed. By age 19 months, 65 (84%) of 77 active children had received one dose of measles-mumps-rubella vaccine (MMR), compared to 82 (67%) of 123 inactive children (risk ratio [RR]=1.3; 95% confidence interval [CI], 1.1- 1.5). By age 25 months, 64 (83%) active children had received four doses of diphtheria-tetanus-pertussis vaccine (DTP), one MMR, and three doses of Haemophilus influenzae type b vaccine (Hib), compared with 64 (52%) inactive children (RR=1.6; 95% CI, 1.3-2.0). CONCLUSIONS: In this cohort, children active in WIC after their first birthday were more likely to be immunized by ages 19 and 25 months, compared with those who were no longer active. Chicago children who drop out of WIC may represent those at highest risk for underimmunization and may require special strategies to improve coverage.

Emergence of pork carnitas as a cause of foodborne disease outbreaks in Chicago.

Carnitas are fried chunks of pork frequently served in Mexican-origin households, food service establishments, and social gatherings. During 1995-2002, carnitas emerged as the most frequently implicated vehicle of transmission in foodborne disease outbreaks in Chicago. Five (6%) of 90 foodborne disease outbreaks investigated and reported in Chicago during this period were linked to carnitas, and they accounted for 108 illnesses and 11 hospitalizations. The etiologic agent in four outbreaks was Salmonella, and these outbreaks accounted for 29% of the 14 Salmonella-associated foodborne disease outbreaks in Chicago during this period. Unsafe food handling practices that occurred after cooking were identified as contributing to multiple carnitas-associated outbreaks. Local health departments that serve significant Mexican-origin populations should be aware of carnitas as a potential source of foodborne disease, particularly salmonellosis.