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Other viral infections
Published in Hung N. Winn, Frank A. Chervenak, Roberto Romero, Clinical Maternal-Fetal Medicine Online, 2021
Prior to vaccination, measles were very contagious with an attack rate of approximately 90% in the nonimmune patient. Transmission is by respiratory droplets with the mucosa of the nose, oropharynx, or conjunctivas as the portal of entry. The usual incubation period is 10 to 14 days but may be as short as 7 days. The patient is infectious for 2 to 3 days prior to symptoms and 3 to 4 days after the appearance of the rash.
TIME-SPACE CLUSTERING OF DISEASE
Published in Richard G. Cornell, Statistical Methods for Cancer Studies, 2020
As just noted, both the method by Walter and the method by Mathen and Chakraborty assume in the null case that all members of the study population who are assumed to be susceptible are at equal risk to the disease. This assumption may be reasonable, for example, when an infectious disease such as influenza enters a population in which there is no prior immunity. However, for many diseases the attack rate is very much influenced by factors such as a person’s age, sex, area of residence or immune status. In such situations, the assumption of equal susceptibility of all members of the population may produce a significant statistical test of aggregation of cases within households due solely to variation in the susceptibility status of members of different households.
The Great Influenza
Published in Rae-Ellen W. Kavey, Allison B. Kavey, Viral Pandemics, 2020
Rae-Ellen W. Kavey, Allison B. Kavey
These days, mortality from the flu averages less than 1%, usually in the elderly or those with underlying lung disease. Based on autopsy studies, about one third of people who die from flu-related causes expire because the virus overwhelms the immune system; another third die from the response to secondary bacterial infections, usually in the lungs; and the remaining third perish due to the failure of one or more other organs. According to the World Health Organization: “Every winter, influenza occurs globally with an annual attack rate estimated at 5%–10% in adults and 20%–30% in children. Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness, and about 250,000 to 500,000 deaths.”9 The attack rate is defined as the proportion of those who become ill after a specified exposure: for the influenza virus, the true asymptomatic fraction is difficult to define, varying from a low mean of 16% in outbreak investigations to as high as 85% in longitudinal studies where infection was defined using serology.10 It is safe to say that a significant proportion of those who are infected with the influenza virus develop a symptomatic illness.
Public health impact of the Pfizer-BioNTech COVID-19 vaccine (BNT162b2) in the first year of rollout in the United States
Published in Journal of Medical Economics, 2022
Manuela Di Fusco, Kinga Marczell, Kristen A. Deger, Mary M. Moran, Timothy L. Wiemken, Alejandro Cane, Solène de Boisvilliers, Jingyan Yang, Shailja Vaghela, Julie Roiz
Individuals entered the Markov model (Figure 1; Table 1) in the “susceptible” or “recovered” health states with weekly cycles for one full year. At each weekly cycle, individuals could transition to other health states or remain in the current state. From the susceptible state, individuals could become infected or receive the vaccine (dose 1 with partial vaccination followed by dose 2 of full vaccination). An age-dependent yearly attack rate in the susceptible population defined the share of the model cohort that would become infected with COVID-19 and vaccination was determined by age-dependent vaccine coverage (further explained in model parameters). From the vaccinated states, patients could experience breakthrough infections or become susceptible again due to waning of vaccine protection. The former was governed by the vaccine efficacy, which could vary by dose, age group and the circulating variants of COVID-19. Waning of the efficacy of the vaccine and of infection-induced immunity was captured through their corresponding duration of protection. In each cycle of the Markov model, a fraction of the cohort was moved from the “vaccinated” (1 or 2 doses) and “recovered” health states to the “susceptible” health state, representing the gradual decrease of protection level in the population due to waning.
Is there a need for pneumococcal vaccination programs for the homeless to prevent invasive pneumococcal disease?
Published in Expert Review of Vaccines, 2021
Gregory Tyrrell, Cerina Lee, Dean Eurich
Canada. A significant amount of data describing increases in IPD among the homeless has come from Canada over the last twenty years. Work from Edmonton, Canada, studying bacteremic pneumococcal pneumonia from 2000 to 2002 found a pneumococcal disease attack rate in the homeless population of 267 infections/100,000 person years [19]. This was 27 times higher than the overall attack rate of 10 infections/100,000 person years in the general population. A population-based surveillance study for IPD in homeless adults took place in Toronto, Canada, from 2002 to 2006 and showed similar rates. These investigators identified an incidence of 273 infections/100,000 persons per year which was 30 times higher than the general population (9 infections/100,000 persons per year) [27]. It was further noted that homeless persons in Toronto accounted for 0.2% of the population yet accounted for 6.6% of all cases of IPD [27]. The most common serotypes associated with IPD in the homeless in Toronto vs the housed populations were serotypes 12F (26% in the homeless versus 5.4% in the housed), 4 (16% versus 7.7%), 22 F (9.7% versus 6.7%) and 7 F (8.1% versus 3.5%) (Table 1) [27]. These four serotypes occurred in higher percentages of IPD in the homeless than cases that occurred in the housed population.
Mechanisms of bacillary dysentery: lessons learnt from infant rabbits
Published in Gut Microbes, 2020
Shigella flexneri is the causative agent of bacillary dysentery (blood in stool) in humans.1 There are more than 270 million cases of shigellosis annually, resulting in more than 200,000 deaths.2 This inflammatory disease is characterized by a dramatic ulceration of the colonic mucosa,3,4 herein referred to as epithelial fenestration. S. flexneri is transmitted via the fecal-oral route and is extremely contagious. Studies in human volunteers showed that the attack rate is above 90% with an infectious dose as low as 100–1000 bacteria per individual.5 Infected patients are usually treated with fluid replacement and antibiotics. The lack of an effective vaccine and the emergence of multiple antimicrobial-resistant (AMR) strains are a major health concern worldwide.6