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Volume 11, Number 9—September 2005

Volume 11, Number 9—September 2005   PDF Version [PDF - 7.89 MB - 171 pages]

Perspective

  • Canine Rabies Ecology in Southern Africa PDF Version [PDF - 206 KB - 6 pages]
    J. Bingham
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    Understanding the persistence of rabies in multiple canine hosts in southern Africa requires applying the principles of metapopulation biology.

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    Rabies is a widespread disease in African domestic dogs and certain wild canine populations. Canine rabies became established in Africa during the 20th century, coinciding with ecologic changes that favored its emergence in canids. I present a conceptual and terminologic framework for understanding rabies ecology in African canids. The framework is underpinned by 2 distinct concepts: maintenance and persistence. Maintenance encompasses the notion of indefinite transmission of infection within a local population and depends on an average transmission ratio >1. Maintenance in all local populations is inherently unstable, and the disease frequently becomes extinct. Persistence, the notion of long-term continuity, depends on the presence of rabies in >1 local population within the canine metapopulation at any time. The implications for understanding rabies ecology and control are reviewed, as are previous studies on rabies ecology in African canids.

Synopses

  • Achieving Operational Hydrologic Monitoring of Mosquitoborne Disease PDF Version [PDF - 482 KB - 8 pages]
    J. Shaman and J. F. Day
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    West Nile virus transmission in Florida can be monitored by using modeled hydrology.

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    Mosquitoes and mosquitoborne disease transmission are sensitive to hydrologic variability. If local hydrologic conditions can be monitored or modeled at the scales at which these conditions affect the population dynamics of vector mosquitoes and the diseases they transmit, a means for monitoring or modeling mosquito populations and mosquitoborne disease transmission may be realized. We review how hydrologic conditions have been associated with mosquito abundances and mosquitoborne disease transmission and discuss the advantages of different measures of hydrologic variability. We propose that the useful application of any measure of hydrologic conditions requires additional consideration of the scales for both the hydrologic measurement and the vector control interventions that will be used to mitigate an outbreak of vectorborne disease. Our efforts to establish operational monitoring of St. Louis encephalitis virus and West Nile virus transmission in Florida are also reviewed.

Research

  • Variant Creutzfeldt-Jakob Disease Death, United States PDF Version [PDF - 179 KB - 4 pages]
    E. D. Belay et al.
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    Reports of secondary bloodborne transmission of vCJD add to the uncertainty about the future of the vCJD outbreak.

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    The only variant Creutzfeldt-Jakob disease (vCJD) patient identified in the United States died in 2004, and the diagnosis was confirmed by analysis of autopsy tissue. The patient likely acquired the disease while growing up in Great Britain before immigrating to the United States in 1992. Additional vCJD patients continue to be identified outside the United Kingdom, including 2 more patients in Ireland, and 1 patient each in Japan, Portugal, Saudi Arabia, Spain, and the Netherlands. The reports of bloodborne transmission of vCJD in 2 patients, 1 of whom was heterozygous for methionine and valine at polymorphic codon 129, add to the uncertainty about the future of the vCJD outbreak.

  • Potential Impact of Antiviral Drug Use during Influenza Pandemic PDF Version [PDF - 559 KB - 8 pages]
    R. Gani et al.
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    Impact of different antiviral treatment strategies on hospitalizations during an influenza pandemic is evaluated.

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    The recent spread of highly pathogenic strains of avian influenza has highlighted the threat posed by pandemic influenza. In the early phases of a pandemic, the only treatment available would be neuraminidase inhibitors, which many countries are considering stockpiling for pandemic use. We estimate the effect on hospitalization rates of using different antiviral stockpile sizes to treat infection. We estimate that stockpiles that cover 20%–25% of the population would be sufficient to treat most of the clinical cases and could lead to 50% to 77% reductions in hospitalizations. Substantial reductions in hospitalization could be achieved with smaller antiviral stockpiles if drugs are reserved for persons at high risk.

  • Fluoroquinolone-resistant Escherichia coli, Indonesia PDF Version [PDF - 127 KB - 7 pages]
    K. Kuntaman et al.
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    High prevalence may be due to clonal spread and emergence of resistant strains.

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    In a recent, population-based survey of 3,996 persons in Indonesia, fluoroquinolone (FQ)-resistant Escherichia coli was prevalent in the fecal flora of 6% of patients at hospital admission and 23% of patients at discharge, but not among healthy relatives or patients visiting primary healthcare centers (2%). Molecular typing showed extensive genetic diversity with only limited clonality among isolates. This finding suggests that independent selection of resistant mutants occurs frequently. FQ-resistant isolates exhibited a higher rate of spontaneous mutation, but sparser virulence profiles, than FQ-susceptible isolates from the same population. The resistant isolates belonged predominantly to phylogenetic groups A (57%) and B1 (22%) but also to the moderately virulent group D (20%). Hypervirulent strains from the B2 cluster were underrepresented (1%). Because FQ-resistant E. coli can cause disease, especially nosocomial infections in immunocompromised patients, spread of such strains must be stopped.

  • Dead Crow Density and West Nile Virus Monitoring, New York PDF Version [PDF - 255 KB - 6 pages]
    M. Eidson et al.
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    Persons in counties with high dead crow densities had elevated risk for disease.

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    New York State used the health commerce system to monitor the number of West Nile virus (WNV) human disease cases and the density of dead crows. In each year from 2001 to 2003 and for the 3 years combined, persons living in New York counties (excluding New York City) with elevated weekly dead crow densities (above a threshold value of 0.1 dead crows per square mile) had higher risk (2.0–8.6 times) for disease caused by WNV within the next 2 weeks than residents of counties reporting fewer dead crows per square mile. This type of index can offer a real-time, relatively inexpensive window into viral activity in time for prevention and control. Changes in reporting, bird populations, and immunity may require that thresholds other than 0.1 be used in later years or in other areas.

  • Dengue Virus Type 3, Brazil, 2002 PDF Version [PDF - 88 KB - 6 pages]
    R. Nogueira et al.
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    An explosive epidemic of DENV-3 in 2002 was the most severe dengue epidemic reported in Brazil since dengue viruses were introduced.

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    During the summer of 2002, Rio de Janeiro had a large epidemic of dengue fever; 288,245 cases were reported. A subset of 1,831 dengue hemorrhagic fever cases occurred. In this study, performed in the first half of 2002, samples from 1,559 patients with suspected cases of dengue infection were analyzed. From this total, 1,497 were obtained from patients with nonfatal cases, and 62 were obtained from patients with fatal cases. By the use of different methods, 831 (53.3%) cases, including 40 fatal cases, were confirmed as dengue infection. When virus identification was successful, dengue virus type 3 (DENV-3) was obtained in 99% of cases. Neurologic involvement was shown in 1 patient with encephalitis, confirmed by the detection of DENV-3 RNA in the cerebrospinal fluid. This explosive epidemic of DENV-3 was the most severe dengue epidemic reported in Brazil since dengue viruses were introduced in 1986.

  • Trypanosomiasis Control, Democratic Republic of Congo, 1993–2003 PDF Version [PDF - 204 KB - 7 pages]
    P. Lutumba et al.
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    Efforts to control human trypanosomiasis, which sharply reduced the disease, must be sustained.

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    In the Democratic Republic of Congo (DRC), human African trypanosomiasis (HAT) reached unprecedented levels in the 1990s. To assess recent trends and evaluate control efforts, we analyzed epidemiologic and financial data collected by all agencies involved in HAT control in DRC from 1993 to 2003. Funds allocated to control populations, as well as to the population screened, doubled from 1993 to 1997 and from 1998 to 2003. The number of cases detected decreased from 26,000 new cases per year in 1998 to 11,000 in 2003. Our analysis shows that HAT control in DRC is almost completely dependent on international aid and that sudden withdrawal of such aid in 1990 had a long-lasting effect. Since 1998, control efforts intensified because of renewed donor interest, including a public-private partnership, and this effort led to a major reduction in HAT incidence. To avoid reemergence of this disease, such efforts should be sustained.

  • Persistence of Resistant Staphylococcus epidermidis after Single Course of Clarithromycin PDF Version [PDF - 127 KB - 5 pages]
    M. Sjölund et al.
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    Short course of antimicrobial therapy can select resistant bacteria that persist for 4 years or longer.

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    We examined how a common therapy that includes clarithromycin affects normally colonizing Staphylococcus epidermidis. Samples from the nostrils of 5 patients receiving therapy were collected before, immediately after, 1 year after, and 4 years after treatment. From each patient and sample, S. epidermidis strains were isolated and analyzed for clarithromycin susceptibility and presence of the erm(C) gene. We show that macrolide-resistant strains of S. epidermidis were selected during therapy and that the same resistant strain may persist for 4 years, in the absence of further antimicrobial treatment.

  • Simulated Anthrax Attacks and Syndromic Surveillance PDF Version [PDF - 100 KB - 5 pages]
    J. D. Nordin et al.
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    Bioterrorism surveillance systems can be assessed using modeling to simulate real-world attacks.

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    We measured sensitivity and timeliness of a syndromic surveillance system to detect bioterrorism events. A hypothetical anthrax release was modeled by using zip code population data, mall customer surveys, and membership information from HealthPartners Medical Group, which covers 9% of a metropolitan area population in Minnesota. For each infection level, 1,000 releases were simulated. Timing of increases in use of medical care was based on data from the Sverdlovsk, Russia, anthrax release. Cases from the simulated outbreak were added to actual respiratory visits recorded for those dates in HealthPartners Medical Group data. Analysis was done by using the space-time scan statistic. We evaluated the proportion of attacks detected at different attack rates and timeliness to detection. Timeliness and completeness of detection of events varied by rate of infection. First detection of events ranged from days 3 to 6. Similar modeling may be possible with other surveillance systems and should be a part of their evaluation.

  • West Nile Virus–infected Mosquitoes, Louisiana, 2002 PDF Version [PDF - 120 KB - 6 pages]
    M. S. Godsey et al.
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    Culex quinquefasciatus was identified as probable vector.

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    Human cases of West Nile virus (WNV) disease appeared in St. Tammany and Tangipahoa Parishes in southeastern Louisiana in June 2002. Cases peaked during July, then rapidly declined. We conducted mosquito collections from August 3 to August 15 at residences of patients with confirmed and suspected WNV disease to estimate species composition, relative abundance, and WNV infection rates. A total of 31,215 mosquitoes representing 25 species were collected by using primarily gravid traps and CO2-baited light traps. Mosquitoes containing WNV RNA were obtained from 5 of 11 confirmed case sites and from 1 of 3 sites with non-WNV disease. WNV RNA was detected in 9 mosquito pools, including 7 Culex quinquefasciatus, 1 Cx. salinarius, and 1 Coquillettidia perturbans. Mosquito infection rates among sites ranged from 0.8/1,000 to 10.9/1,000. Results suggest that Cx. quinquefasciatus was the primary epizootic/epidemic vector, with other species possibly playing a secondary role.

  • Legionellosis from Legionella pneumophila Serogroup 13 PDF Version [PDF - 143 KB - 5 pages]
    B. Faris et al.
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    Legionella pneumophila serogroup 13 may be underrecognized.

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    We describe 4 cases of Legionella pneumophila serogroup 13–associated pneumonia. These cases originate from a broad geographic range that includes Scotland, Australia, and New Zealand. L. pneumophila serogroup 13 pneumonia has a clinically diverse spectrum that ranges from relatively mild, community-acquired pneumonia to potentially fatal severe pneumonia with multisystem organ failure. All cases were confirmed by culture and direct fluorescent antibody staining or indirect immunofluorescent antibody tests. Proven or putative sources of L. pneumophila serogroup 13 infections in 2 patients included a contaminated whirlpool spa filter and river water. An environmental source was not found in the remaining 2 cases; environmental cultures yielded only other L. pneumophila serogroups or nonpneumophila Legionella species. We describe the clinical and laboratory features of L. pneumophila serogroup 13 infections. L. pneumophila serogroup 13 pneumonia is rarely reported, but it may be an underrecognized pathogenic serogroup of L. pneumophila.

  • Malaria Attributable to the HIV-1 Epidemic, Sub-Saharan Africa PDF Version [PDF - 401 KB - 10 pages]
    E. L. Korenromp et al.
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    The HIV-1 epidemic has increased the malaria disease and death rate in southern Africa.

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    We assessed the impact of HIV-1 on malaria in the sub-Saharan African population. Relative risks for malaria in HIV-infected persons, derived from literature review, were applied to the HIV-infected population in each country, by age group, stratum of CD4 cell count, and urban versus rural residence. Distributions of CD4 counts among HIV-infected persons were modeled assuming a linear decline in CD4 after seroconversion. Averaged across 41 countries, the impact of HIV-1 was limited (although quantitatively uncertain) because of the different geographic distributions and contrasting age patterns of the 2 diseases. However, in Botswana, Zimbabwe, Swaziland, South Africa, and Namibia, the incidence of clinical malaria increased by <28% (95% confidence interval [CI] 14%–47%) and death increased by <114% (95% CI 37%–188%). These effects were due to high HIV-1 prevalence in rural areas and the locally unstable nature of malaria transmission that results in a high proportion of adult cases.

  • Molecular Epidemiology of SARS-associated Coronavirus, Beijing PDF Version [PDF - 219 KB - 5 pages]
    W. Liu et al.
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    Viral adaptation to the host may be occurring under selective immune pressure.

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    Single nucleotide variations (SNVs) at 5 loci (17564, 21721, 22222, 23823, and 27827) were used to define the molecular epidemiologic characteristics of severe acute respiratory syndrome–associated coronavirus (SARS-CoV) from Beijing patients. Five fragments targeted at the SNV loci were amplified directly from clinical samples by using reverse transcription–polymerase chain reaction (RT-PCR), before sequencing the amplified products. Analyses of 45 sequences obtained from 29 patients showed that the GGCTC motif dominated among samples collected from March to early April 2003; the TGTTT motif predominanted afterwards. The switch from GGCTC to TGTTT was observed among patients belonging to the same cluster, which ruled out the possibility of the coincidental superposition of 2 epidemics running in parallel in Beijing. The Beijing isolates underwent the same change pattern reported from Guangdong Province. The same series of mutations occurring in separate geographic locations and at different times suggests a dominant process of viral adaptation to the host.

Historical Review

  • Malaria in Kenya's Western Highlands PDF Version [PDF - 470 KB - 8 pages]
    G. Shanks et al.
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    Reemergence of epidemics in tea plantations will likely result in antimalarial-drug resistance.

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    Records from tea estates in the Kericho district in Kenya show that malaria reemerged in the 1980s. Renewed epidemic activity coincided with the emergence of chloroquine-resistant Plasmodium falciparum malaria and may have been triggered by the failure of antimalarial drugs. Meteorologic changes, population movements, degradation of health services, and changes in Anopheles vector populations are possible contributing factors. The highland malaria epidemics of the 1940s were stopped largely by sporontocidal drugs, and combination chemotherapy has recently limited transmission. Antimalarial drugs can limit the pool of gametocytes available to infect mosquitoes during the brief transmission season.

Dispatches

Commentaries

Letters

About the Cover

Etymologia

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