West Nile virus, an Old World flavivirus related to St. Louis encephalitis virus, was first recorded in the New World during August 1999 in the borough of Queens, New York City. Through October 1999, 62 patients, 7 of whom died, had confirmed infections with the virus. Ornithophilic mosquitoes are the principal vectors of West Nile virus in the Old World, and birds of several species, chiefly migrants, appear to be the major introductory or amplifying hosts. If transovarial transmission or survival in overwintering mosquitoes were the principal means for its persistence, West Nile virus might not become established in the New World because of aggressive mosquito suppression campaigns conducted in the New York area. However, the pattern of outbreaks in southern Europe suggests that viremic migratory birds may also contribute to movement of the virus. If so, West Nile virus has the potential to cause outbreaks throughout both temperate and tropical regions of the Western Hemisphere.

Bacteria that are vertically transmitted through female hosts and kill male hosts that inherit them were first recorded in insects during the 1950s. Recent studies have shown these "male-killers" to be diverse and have led to a reappraisal of the biology of many groups of bacteria. Rickettsia, for instance, have been regarded as human pathogens transmitted by arthropods. The finding of a male-killing Rickettsia obligately associated with an insect suggests that the genus' members may be primarily associated with arthropods and are only sometimes pathogens of vertebrates. We examined both how killing of male hosts affects the dynamics of inherited bacteria and how male-killing bacteria affect their host populations. Finally, we assessed the potential use of these microorganisms in the control of insect populations.

Communication theory and techniques, aided by the electronic revolution, provide new opportunities and challenges for the effective transfer of laboratory, epidemiologic, surveillance, and other public health data to the public who funds them. We review the applicability of communication theory, particularly the audience-source-message-channel meta-model, to emerging infectious disease issues. Emergence of new infectious organisms, microbial resistance to therapeutic drugs, and increased emphasis on prevention have expanded the role of communication as a vital component of public health practice. In the absence of cure, as in AIDS and many other public health problems, an effectively crafted and disseminated prevention message is the key control measure. Applying communication theory to disease prevention messages can increase the effectiveness of the messages and improve public health.

We analyzed pertussis reporting, death, hospitalization, and serodiagnostic data from 1976 to 1998 to help explain the cause of the 1996 pertussis outbreak in the Netherlands. The unexpected outbreak was detected by an increase in pertussis reporting and by other surveillance methods. In 1996, according to reporting and serologic data, the increase in pertussis incidence among (mostly unvaccinated) children less than 1 year of age was similar to the increase in hospital admissions. Among older (mostly vaccinated) persons, the increase in hospital admissions was relatively small. The increase in pertussis incidence was higher among vaccinated than among unvaccinated persons of all ages. This resulted in lower estimates of vaccine effectiveness. The proportion of pertussis infections resulting in recognizable symptoms may have increased among vaccinated persons because of a mismatch of the vaccine strain and circulating Bordetella pertussis strains. The small immunogenicity profile of the Dutch vaccine may have resulted in greater vulnerability to antigenic changes in B. pertussis.

We conducted a serosurvey among patients of a health center in Hashimiah, a Jordanian town of 30,000 inhabitants located near a wastewater treatment plant and its effluent channel. Serum samples from 261 patients 5 years of age were assessed for immunoglobulin G (IgG) and IgM antibodies against West Nile, sandfly Sicilian, sandfly Naples, and Rift Valley viruses; the seroprevalence of IgG antibodies was 8%, 47%, 30%, and 0%, respectively. Female participants were more likely to have been infected than male. Persons living within 2 km of the treatment plant were more likely to have been infected with West Nile (p=0.016) and sandfly Sicilian (p=0.010) viruses. Raising domestic animals within the house was a risk factor for sandfly Sicilian (p=0.003) but not for sandfly Naples virus (p=0.148). All serum samples were negative for IgM antibodies against the tested viruses. Our study is the first documentation of West Nile and sandfly viruses in Jordan and calls attention to the possible health hazards of living close to wastewater treatment plants and their effluent channels.

We analyzed dual-capture data collected during longitudinal studies monitoring transmission and persistence of Sin Nombre virus in rodents in Colorado.Our data indicate that multiple captures (two or more rodents captured in a single trap) may not be random, as indicated in previous studies, but rather the result of underlying, species-specific social behavior or cohesiveness. In the pairs we captured, most often, rodents were of the same species, were male, and could be recaptured as pairs. Therefore, dual captures of rodents, which are unusual but not rare, tend to occur among certain species, and appear to be nonrandom, group-foraging encounters. These demographic and ecological characteristics may have implications for the study of the transmission of hantavirus.

An outbreak of encephalitis occurred in New York City in late August 1999, the first caused by West Nile virus in North America. Histopathologic and immunopathologic examinations performed on human autopsy materials helped guide subsequent laboratory and epidemiologic investigations that led to identification of the etiologic agent.

From July to September 1999, a widespread outbreak of meningoencephalitis associated with West Nile virus (Flavivirus, Flaviviridae) occurred in southern Russia, with hundreds of cases and dozens of deaths. Two strains of West Nile virus isolated from patient serum and brain-tissue samples reacted in hemagglutination-inhibition and neutralization tests with patients' convalescent-phase sera and immune ascites fluid from other strains of West Nile virus.

A healthy 13-year-old boy who had spent the first 4.5 years of his life in an orphanage in Thailand before adoption by an American couple became ill with subacute sclerosing panencephalitis and died several months later. The boy had most likely contracted wild-type measles in Thailand. Measles complications are a risk in international adoptions.

We report the first case of endocarditis caused by a Gordonia species genetically related to G. sputi but exhibiting some atypical biochemical features in a 31-year-old woman with a central venous catheter. This unusual pathogen may be a new cause of opportunistic infections in patients with severe underlying diseases.

From 1996 through 1999, 35 deer mice (Peromyscus maniculatus) were captured in 25 urban and suburban homes in southwestern Montana. Mice were captured throughout the year except for January; seven mice (20%) from seven (28%) of the homes were seropositive for Sin Nombre virus. The infected mice were mostly adult males captured in the spring and fall.

A 37-year-old man living in eastern France seroconverted to Rickettsia helvetica in August 1997, 4 weeks after the onset of an unexplained febrile illness. Results of a serosurvey of forest workers from the area where the patient lived showed a 9.2% seroprevalence against R. helvetica. This organism may pose a threat for populations exposed to Ixodes ricinus ticks.

Surveillance of 2,277 white-tailed deer for antibodies against Ehrlichia chaffeensis in Iowa showed seropositivity rates of 12.5% in 1994 and 13.9% in 1996. From 1994 to 1996, the estimated number of seropositive deer increased to 54,701 (28%). The increasing deer population and expanding tick distribution may increase risk for human monocytic ehrlichiosis.

During 1990 to 1998, we identified multidrug-resistant isolates of Salmonella Enteritidis in southern Italy. Plasmids containing class I integrons and codifying for synthesis of extended-spectrum ß-lactamases were detected. Active surveillance for resistance to antimicrobial agents is needed to guard against the possible spread of resistant clones.

Improved surveillance indicates that Lyme borreliosis, an emerging zoonosis in the United Kingdom, has increased from 0.06/100,000 during 1986-1992 to 0.32/100,000 since 1996. Case reports peaked in the third quarter of each year. Several high-incidence localities were identified. Erythema migrans was reported in 41% of patients; arthritis in 4%; musculoskeletal symptoms in 18%; and neuroborreliosis in 15%.

During the 1998 hunting season in Delaware, 1,480 ticks were collected from 252 white-tailed deer; 98% were Ixodes scapularis, a significant increase from the 85% reported in 1988. Ticks were tested for Borrelia burgdorferi and the causative agent of human granulocytic ehrlichiosis. Infection rates remained stable in New Castle and Kent Counties, but increased from < 1% to 8% in Sussex County.

A sentinel group of primary-care physicians in Wales actively reported cases of acute bloody diarrhea from February 1997 through December 1998. The estimated annual rate was 18 cases per 100,000 population. Most (80%) cases were due to Campylobacter or Salmonella; however, 18% were undiagnosed.

A large outbreak of adenovirus type 4-associated acute respiratory disease (ARD) occurred at Fort Jackson, South Carolina, in 1997. A laboratory-based ARD surveillance program was initiated at Fort Gordon, Georgia, where advanced individual training was heavily populated with Fort Jackson soldiers. Adenovirus type 4 was isolated from 50% of 147 trainees hospitalized with ARD. Most (88%) introduced cases were in trainees from Fort Jackson.

The incidence of enteric fever caused by Salmonella enterica serotype Paratyphi A has been increasing in India since 1996. In 1998, the incidence of enteric fever caused by drug-resistant S. Paratyphi A abruptly increased in the New Delhi region. In the first 6 months of 1999, 32% of isolates were resistant to both chloramphenicol and cotrimoxazole and another 13% were resistant to more than two antibiotics.

A widespread epidemic of dengue hemorrhagic fever (DHF) occurred in southern Vietnam in 1998, with 438.98 cases/100,000 population and 342 deaths. The number of DHF cases and deaths per 100,000 population increased 152.4% and 151.8% over a 1997 epidemic. Dengue viruses were isolated from 143 patient blood samples; DEN-3 virus was identified as the predominant serotype, although a resurgence of DEN-4 was noted.

We tested 758 fecal Escherichia coli isolates, recovered from Nigerian students in 1986, 1988, 1990, 1994, and 1998, for susceptibility to seven antimicrobial drugs. The prevalence of strains resistant to tetracycline, ampicillin, chloramphenicol, and streptomycin were 9% to 35% in 1986 and 56% to 100% in 1998. These findings demonstrate that resistance gene reservoirs are increasing in healthy persons.