Patterns of exposure and severity of measles infection. Copenhagen 1915-1925

Symptom propagation in respiratory pathogens of public health concern: a review of the evidence

Symptom propagation occurs when the symptom set an individual experiences is correlated with the symptom set of the individual who infected them. Symptom propagation may dramatically affect epidemiological outcomes, potentially causing clusters of severe disease. Conversely, it could result in chains of mild infection, generating widespread immunity with minimal cost to public health. Despite accumulating evidence that symptom propagation occurs for many respiratory pathogens, the underlying mechanisms are not well understood. Here, we conducted a scoping literature review for 14 respiratory pathogens to ascertain the extent of evidence for symptom propagation by two mechanisms: dose-severity relationships and route-severity relationships. We identify considerable heterogeneity between pathogens in the relative importance of the two mechanisms, highlighting the importance of pathogen-specific investigations. For almost all pathogens, including influenza and SARS-CoV-2, we found support for at least one of the two mechanisms. For some pathogens, including influenza, we found convincing evidence that both mechanisms contribute to symptom propagation. Furthermore, infectious disease models traditionally do not include symptom propagation. We summarize the present state of modelling advancements to address the methodological gap. We then investigate a simplified disease outbreak scenario, finding that under strong symptom propagation, isolating mildly infected individuals can have negative epidemiological implications.

Measles Infection Dose Responses: Insights from Mathematical Modeling

How viral infections develop can change based on the number of viruses initially entering the body. The understanding of the impacts of infection doses remains incomplete, in part due to challenging constraints, and a lack of research. Gaining more insights is crucial regarding the measles virus (MV). The higher the MV infection dose, the earlier the peak of acute viremia, but the magnitude of the peak viremia remains almost constant. Measles is highly contagious, causes immunosuppression such as lymphopenia, and contributes substantially to childhood morbidity and mortality. This work investigated mechanisms underlying the observed wild-type measles infection dose responses in cynomolgus monkeys. We fitted longitudinal data on viremia using maximum likelihood estimation, and used the Akaike Information Criterion (AIC) to evaluate relevant biological hypotheses and their respective model parameterizations. The lowest AIC indicates a linear relationship between the infection dose, the initial viral load, and the initial number of activated MV-specific T cells. Early peak viremia is associated with high initial number of activated MV-specific T cells. Thus, when MV infection dose increases, the initial viremia and associated immune cell stimulation increase, and reduce the time it takes for T cell killing to be sufficient, thereby allowing dose-independent peaks for viremia, MV-specific T cells, and lymphocyte depletion. Together, these results suggest that the development of measles depends on virus-host interactions at the start and the efficiency of viral control by cellular immunity. These relationships are additional motivations for prevention, vaccination, and early treatment for measles.

Measles in the European Past: Outbreak of Severe Measles in an Isolated German Village, 1861

OBJECTIVES

We examined measles mortality in the European past in an outbreak in an isolated German village, Hagelloch, in 1861.

METHODS

Pfeilsticker's contemporary thesis was used to describe the measles case fatality ratio (CFR) and complications. Data on onset of prodromes and rash was used to determine index cases and secondary cases of measles within the household. The church register provided information on survival in 1862.

RESULTS

The epidemic affected nearly all children under 14 years of age. The overall CFR was 6.4%(12/187), and 10%(7/70) for children under five years of age; 44% of children were secondary cases (82/187). Secondary cases had higher CFR than index cases (RR=3.03 (95% CI: 0.91-10.07). Boys had higher CFR than girls (RR=4.46 (1.03-19.22)). Boys infected by a girl had higher CFR than boys infected by other boys (RR=6.30 (1.18-85.64)). Children who survived measles virus infection in 1861, did not have higher mortality in the following year compared with those who had not had measles in 1861 (RR=0.24 (0.07-0.82)).

CONCLUSIONS

Severe measles in the European past had determinants similar to those observed more recently in low-income countries.

BRIEF SUMMARY

The measles case fatality was 6% in rural Germany in 1861. Mortality was highest for boys infected in the household by a girl. There was no excess mortality after the acute phase of measles infection.

Pediatric COVID-19 case with regard to the family infection chain and the psychosocial context

The role of children in households, spreading SARS-CoV-2, may differ from measles or influenza, and therefore, these diseases are not directly comparable to COVID-19. The psychosocial aspect of infection and quarantine for families and children suggests that fear of social stigmatization can lead to not disclosing the infection.

Sex differences in the effect of vaccines on the risk of hospitalization due to measles in Guinea-bissau

BACKGROUND

Routine immunizations have non-specific and sex-differential effects on childhood mortality and morbidity in low-income countries; BCG and measles vaccine (MV) may reduce and diphtheria-tetanus-pertussis vaccine (DTP) may increase the mortality of girls relative to boys.

SETTING

Urban area in Guinea-Bissau, with a demographic surveillance system and registration of all pediatric hospitalizations. Guinea-Bissau experienced a large outbreak of measles infection in 2003-2004.

DESIGN

We used hospital and community data to examine the impact of other vaccines on the risk of hospitalizations for measles infection. Vaccine efficacy (VE) against hospitalization for children aged 6 to 59 months of age was examined. We assessed whether VE depended on vaccination status for other vaccines and whether the pattern differed for boys and girls.

MAIN OUTCOME MEASURE

Sex-specific vaccine efficacy against hospitalization for children aged 6 to 59 months of age.

RESULTS

The VE depended on sex and the sequence of vaccinations. The VE of MV against hospitalization for measles was better for girls than for boys. Among children who had received MV as the most recent vaccine VE against hospitalization was as high as 96% for girls, but only 81% for boys (P = 0.002). Among children who had received DTP simultaneously with MV or DTP after MV, VE declined for girls (91%) and increased for boys (90%). Compared with having received MV as most recent vaccination, DTP simultaneously with MV or DTP after MV improved the efficacy significantly for boys and the effect was significantly different for boys and girls (P = 0.023). The female-male risk ratio of hospitalization varied significantly, depending on the most recent vaccination (P = 0.014); it was 0.28 (0.11-0.68) for MV alone, but 1.21 (0.82-1.77) for DTP but no MV, and 1.13 (0.58-2.18) for DTP simultaneously with MV or after MV. Among MV-unvaccinated children, BCG-vaccinated girls had a lower risk of measles hospitalization than DTP-vaccinated girls (RR=0.0 (0.0-0.99), exact test).

Varicella zoster in Guinea-Bissau: intensity of exposure and severity of infection

OBJECTIVE

To describe the epidemiology of and risk factors for severe chickenpox in Guinea- Bissau.

METHODS

A prospective household study in a semiurban area of the capital. Severity was assessed by number of pox, fever response and presence of pneumonia. Severity was compared for the first case in a house, that is, the index case, and the secondary cases infected at home.

RESULT

We identified 1539 cases of chickenpox. The median age was lower for boys and secondary cases (both P < 0.03); 44.6% of children were 1-4 years of age. The likely minimum interval between index and secondary cases was 10 days; most secondary cases occurred 14-17 days after the index case. The length of the incubation period was related to the intensity of exposure (P < 0.01). The number of pox was higher for secondary cases (P < 0.01) and was related to intensity of exposure (P < 0.01). Secondary cases had higher fever and more frequently pneumonia (relative risk, 2.17; 95% confidence interval, 1.54-3.08). Children with pneumonia were younger and had more pox. Nutritional status was not related to severity.

CONCLUSIONS

Age and intensity of exposure are important determinants for severity of chickenpox infection. The length of the incubation period depends on intensity of exposure, suggesting that the dose of infection might be important.

Intensity of exposure and severity of whooping cough

OBJECTIVE

To study the association between intensity of exposure and mortality due to pertussis.

METHODS

Overall 3233 historical records from the main fever hospital in Copenhagen were examined. Exposure status of the whooping cough cases was coded as primary, secondary or multiple cases according to information in the hospital records. Primary cases, infected outside the home, were presumably exposed less intensively to the infectious agent compared to secondary cases, who were infected in the family. Multiple cases were from families with several simultaneous cases, but no clear information on transmission between cases.

RESULTS

Case fatality was strongly related to age, being highest among the infants. Other risk factors were sibship size, exposure status and calendar period. In a multivariate analysis, period, age, and exposure status remained significant. Compared to primary cases, secondary cases and multiple cases had a 2.8 [RR = 2.76 (1.37 - 5.56)] and a two-fold [(RR = 1.99 (1.33 - 2.96)] higher risk of dying.

CONCLUSION

Intensity of exposure may be a major determinant of the severity of pertussis infection.

Assumptions and contradictions in measles and measles immunization research: is measles good for something?

Measles infection, the major cause of childhood mortality among infections preventable by immunization, has been considered to kill mainly young and malnourished children. Assuming that mainly 'weak' children are saved by immunizations, it has been speculated that the impact on survival of immunization is likely to be limited because the malnourished children are more prone to die of other infections. However, recent studies from developing countries have suggested that host factors may not be the most important determinants of acute and long-term mortality after measles infection. Instead, it was found that infection contracted after exposure at home infection contracted from someone outside the home. Furthermore, measles is particularly severe if contracted from someone of the opposite sex. Hence transmission factors, in particularly intensity of exposure and cross-sex transmission, may be more important determinants of measles mortality than the determinants of measles mortality than the host factors usually emphasized. Consistent with these observations and in contrast to assumptions about 'weak' children dying, immunization is associated with a major reduction in mortality. Since measles immunization is associated with a 30% reduction in mortality or more, the impact is much larger than should be expected from the proportion of all deaths attributed to measles. It has therefore been suggested that measles immunization may prevent the persistent immunosuppression and delayed mortality assumed to be associated with measles. However, several observations contradict the common understanding that the function of measles immunization is only to prevent the acute and long-term mortality associated with measles infection. Recently, the high-titre measles immunization recommended by WHO was found to be associated with reduced survival for female recipients compared with girls who have received the standard low-dose measles vaccine, and this difference in survival was not due to suboptimal protection against measles infection. Contrary to usual assumptions. against measles infection. Contrary to usual assumptions, standard low-dose measles vaccine reduces mortality even more when given before 9 months of age, the age currently recommended by WHO. The beneficial impact of standard vaccine is apparently temporary, lasting 1 to 2 years, whereas it should increase with the age of the child. The beneficial effect seems to be particularly strong for girls. The most likely interpretation of these observations, is that standard low-dose measles vaccine has a non-specific beneficial effect. Contrary to current assumptions, children who survive the acute phase of measles infection may have a survival advantage compared with unimmunized, uninfected children.(ABSTRACT TRUNCATED AT 400 WORDS)