Population-level analyses often use average quantities to describe heterogeneous systems, particularly when variation does not arise from identifiable groups. A prominent example, central to our current understanding of epidemic spread, is the basic reproductive number, R(0), which is defined as the mean number of infections caused by an infected individual in a susceptible population. Population estimates of R(0) can obscure considerable individual variation in infectiousness, as highlighted during the global emergence of severe acute respiratory syndrome (SARS) by numerous 'superspreading events' in which certain individuals infected unusually large numbers of secondary cases. For diseases transmitted by non-sexual direct contacts, such as SARS or smallpox, individual variation is difficult to measure empirically, and thus its importance for outbreak dynamics has been unclear. Here we present an integrated theoretical and statistical analysis of the influence of individual variation in infectiousness on disease emergence. Using contact tracing data from eight directly transmitted diseases, we show that the distribution of individual infectiousness around R(0) is often highly skewed. Model predictions accounting for this variation differ sharply from average-based approaches, with disease extinction more likely and outbreaks rarer but more explosive. Using these models, we explore implications for outbreak control, showing that individual-specific control measures outperform population-wide measures. Moreover, the dramatic improvements achieved through targeted control policies emphasize the need to identify predictive correlates of higher infectiousness. Our findings indicate that superspreading is a normal feature of disease spread, and to frame ongoing discussion we propose a rigorous definition for superspreading events and a method to predict their frequency.

/pdf/superspreading-and-the-effect-of-individual-variation-on-1hf80n09pb.pdf

Superspreading and the effect of individual variation on disease emergence

Emerging infectious diseases , Emerging infectious diseases , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

/pdf/emerging-infectious-diseases-t66fc9g8n5.pdf

Emerging Infectious Diseases

Crimean-Congo haemorrhagic fever (CCHF) is an often fatal viral infection described in about 30 countries, and it has the most extensive geographic distribution of the medically important tickborne viral diseases, closely approximating the known global distribution of Hyalomma spp ticks. Human beings become infected through tick bites, by crushing infected ticks, after contact with a patient with CCHF during the acute phase of infection, or by contact with blood or tissues from viraemic livestock. Clinical features commonly show a dramatic progression characterised by haemorrhage, myalgia, and fever. The levels of liver enzymes, creatinine phosphokinase, and lactate dehydrogenase are raised, and bleeding markers are prolonged. Infection of the endothelium has a major pathogenic role. Besides direct infection of the endothelium, indirect damage by viral factors or virus-mediated host-derived soluble factors that cause endothelial activations and dysfunction are thought to occur. In diagnosis, enzyme-linked immunoassay and real-time reverse transcriptase PCR are used. Early diagnosis is critical for patient therapy and prevention of potential nosocomial infections. Supportive therapy is the most essential part of case management. Recent studies suggest that ribavirin is effective against CCHF, although definitive studies are not available. Health-care workers have a serious risk of infection, particularly during care of patients with haemorrhages from the nose, mouth, gums, vagina, and injection sites. Simple barrier precautions have been reported to be effective.

/pdf/crimean-congo-haemorrhagic-fever-1mjnt47obh.pdf

Crimean-Congo haemorrhagic fever

ObjectiveTo develop consensus-based recommendations for measures to be taken
by medical and public health professionals if hemorrhagic fever viruses (HFVs)
are used as biological weapons against a civilian populationParticipantsThe Working Group on Civilian Biodefense included 26 representatives
from academic medical centers, public health, military services, governmental
agencies, and other emergency management institutionsEvidenceMEDLINE was searched from January 1966 to January 2002 Retrieved references,
relevant material published prior to 1966, and additional sources identified
by participants were reviewedConsensus ProcessThree formal drafts of the statement that synthesized information obtained
in the evidence-gathering process were reviewed by the working group Each
draft incorporated comments and judgments of the members All members approved
the final draftConclusionsWeapons disseminating a number of HFVs could cause an outbreak of an
undifferentiated febrile illness 2 to 21 days later, associated with clinical
manifestations that could include rash, hemorrhagic diathesis, and shock
The mode of transmission and clinical course would vary depending on the specific
pathogen Diagnosis may be delayed given clinicians' unfamiliarity with these
diseases, heterogeneous clinical presentation within an infected cohort, and
lack of widely available diagnostic tests Initiation of ribavirin therapy
in the early phases of illness may be useful in treatment of some of these
viruses, although extensive experience is lacking There are no licensed vaccines
to treat the diseases caused by HFVs

https://jamanetwork.com/journals/jama/articlepdf/194908/JST20006.pdf

Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management

In studies of Lassa fever in Sierra Leone, the prevalence of human antibody to Lassa virus ranged from 8% to 52%. Mastomys natalensis, the reservoir of Lassa virus, constituted 50%-60% of the rodents captured in houses but only 10%-20% of those captured in surrounding agriculture and bush areas (chi 2 = 90.2, P less than 10(-6), df = 1), a finding suggesting that houses are the most-important location for transmission of Lassa virus. Viral infection of Mastomys from houses ranged from 0% to 80%. The incidence of seroconversions in susceptible persons ranged from 5% to 22% per year; the ratio of illness to infection ranged from 9% to 26%, and the proportion of febrile illness associated with seroconversion was 5%-14%. Eightfold rises in titer of antibody occurred in 1%-18% of the antibody-positive population, a result suggesting reinfection. We estimate the ratio of fatalities to infection to be 1%-2%, a rate lower than estimates based on hospitalized cases. The high incidence of Lassa fever makes it a major problem in West Africa.

https://www.jstor.org/stable/pdfplus/30105053.pdf

A Prospective Study of the Epidemiology and Ecology of Lassa Fever

A restricted, hospital-centred outbreak of Lassa fever involving 28 persons occurred early in 1970 in Jos, Nigeria 24 patients were in hospital Every patient, save the index, could be traced to some prior known human source of infection Complement-fixing antibody to Lassa virus was detected in the sera of only 4 of 172 family and hospital contacts bled These 4 persons had all been ill Animal studies have so far failed to reveal a non-human host

Lassa fever. Epidemiological aspects of the 1970 epidemic, Jos, Nigeria.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

B.E. Henderson

Author Tools

Chat about Author

Papers

Lassa fever. Epidemiological aspects of the 1970 epidemic, Jos, Nigeria.