Nipah virus outbreak with person-to-person transmission in a district of Bangladesh, 2007.

In February 2007 an outbreak of Nipah virus (NiV) encephalitis in Thakurgaon District of northwest Bangladesh affected seven people, three of whom died. All subsequent cases developed illness 7-14 days after close physical contact with the index case while he was ill. Cases were more likely than controls to have been in the same room (100% vs. 9.5%, OR undefined, P<0.001) and to have touched him (83% vs. 0%, OR undefined, P<0.001). Although the source of infection for the index case was not identified, 50% of Pteropus bats sampled from near the outbreak area 1 month after the outbreak had antibodies to NiV confirming the presence of the virus in the area. The outbreak was spread by person-to-person transmission. Risk of NiV infection in family caregivers highlights the need for infection control practices to limit transmission of potentially infectious body secretions.

Genetic identification of a hantavirus associated with an outbreak of acute respiratory illness.

A mysterious respiratory illness with high mortality was recently reported in the southwestern United States. Serologic studies implicated the hantaviruses, rodent-borne RNA viruses usually associated elsewhere in the world with hemorrhagic fever with renal syndrome. A genetic detection assay amplified hantavirus-specific DNA fragments from RNA extracted from the tissues of patients and deer mice (Peromyscus maniculatus) caught at or near patient residences. Nucleotide sequence analysis revealed the associated virus to be a new hantavirus and provided a direct genetic link between infection in patients and rodents.

Nipah virus: a recently emergent deadly paramyxovirus.

A paramyxovirus virus termed Nipah virus has been identified as the etiologic agent of an outbreak of severe encephalitis in people with close contact exposure to pigs in Malaysia and Singapore. The outbreak was first noted in late September 1998 and by mid-June 1999, more than 265 encephalitis cases, including 105 deaths, had been reported in Malaysia, and 11 cases of encephalitis or respiratory illness with one death had been reported in Singapore. Electron microscopic, serologic, and genetic studies indicate that this virus belongs to the family Paramyxoviridae and is most closely related to the recently discovered Hendra virus. We suggest that these two viruses are representative of a new genus within the family Paramyxoviridae. Like Hendra virus, Nipah virus is unusual among the paramyxoviruses in its ability to infect and cause potentially fatal disease in a number of host species, including humans.

Risk factors for Nipah virus encephalitis in Bangladesh.

Nipah virus (NiV) is a paramyxovirus that causes severe encephalitis in humans. During January 2004, twelve patients with NiV encephalitis (NiVE) were identified in west-central Bangladesh. A case-control study was conducted to identify factors associated with NiV infection. NiVE patients from the outbreak were enrolled in a matched case-control study. Exact odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by using a matched analysis. Climbing trees (83% of cases vs. 51% of controls, OR 8.2, 95% CI 1.25-infinity) and contact with another NiVE patient (67% of cases vs. 9% of controls, OR 21.4, 95% CI 2.78-966.1) were associated with infection. We did not identify an increased risk for NiV infection among persons who had contact with a potential intermediate host. Although we cannot rule out person-to-person transmission, case-patients were likely infected from contact with fruit bats or their secretions.

Complete Genome Sequences of a Hantavirus Isolate from New York.

We report here the complete genome sequences for all three segments of the New York hantavirus (New York 1). This is the first reported L segment sequence for hantaviruses maintained in Peromyscus spp. endemic to the eastern United States and Canada.

Human and rodent hantavirus infection in New York State: public health significance of an emerging infectious disease.

BACKGROUND: A case of hantavirus pulmonary syndrome with possible exposure in New York and/or Rhode Island was confirmed in February 1994. OBJECTIVE: To conduct four studies to determine the historical and geographic distribution of human and small-mammal infection with hantaviruses in New York State. METHODS: Enzyme-linked immunosorbent assays were performed on serum samples obtained from 130 humans during a 1978 babesiosis survey, 907 small mammals collected in New York State since 1984, 12 rodents collected in 1994 near the residences of the patients with hantavirus pulmonary syndrome, and 76 New York patients with acute respiratory distress syndrome-like illness (as suspected cases of hantavirus pulmonary syndrome). RESULTS: None of the human serum samples from the 1978 serosurvey showed evidence of hantavirus exposure by enzyme-linked immunosorbent assay. Statewide historical serum samples from white-footed mice showed evidence of Sin Nombre virus infection in 12.0% (97/809) and Seoul-like virus infection in 9.6% (78/809). Site-specific seropositivity rates were as high as 48.5% with Sin Nombre virus during 1 year (1984). Two of 12 mice captured near the residences of a human patient were positive for Sin Nombre virus by enzyme-linked immunosorbent assay, yet were negative for viral RNA by polymerase chain reaction. None of the patients with suspected hantavirus pulmonary syndrome was serologically reactive for Sin Nombre virus. CONCLUSIONS: We provide serologic evidence of small-mammal infection with hantaviruses in New York State as long ago as 1984. Human cases of hantavirus pulmonary syndrome are rare in New York, and data indicate that transmission to humans is probably infrequent. A unique set of host, agent, and environmental factors may be necessary to cause hantavirus pulmonary syndrome in humans.

Discriminators between hantavirus-infected and -uninfected persons enrolled in a trial of intravenous ribavirin for presumptive hantavirus pulmonary syndrome.

To provide a potentially therapeutic intervention and to collect clinical and laboratory data during an outbreak of hantavirus pulmonary syndrome (HPS), 140 patients from the United States with suspected HPS were enrolled for investigational intravenous ribavirin treatment. HPS was subsequently laboratory confirmed in 30 persons and not confirmed in 105 persons with adequate specimens. Patients with HPS were significantly more likely than were hantavirus-negative patients to report myalgias from onset of symptoms through hospitalization, nausea at outpatient presentation, and diarrhea and nausea at the time of hospitalization; they were significantly less likely to report respiratory symptoms early in the illness. The groups did not differ with regard to time from the onset of illness to the point at which they sought care; time from onset, hospitalization, or enrollment to death was significantly shorter for patients with HPS. At the time of hospitalization, patients with HPS more commonly had myelocytes, metamyelocytes, or promyelocytes on a peripheral blood smear, and significantly more of them had thrombocytopenia, hemoconcentration, and hypocapnia. Patterns of clinical symptoms, the pace of clinical evolution, and specific clinical laboratory parameters discriminated between these 2 groups.

Intravenous ribavirin for hantavirus pulmonary syndrome: safety and tolerance during 1 year of open-label experience. Ribavirin Study Group.

Intravenous ribavirin was provided non-selectively for investigational open-label use among persons with suspected hantavirus pulmonary syndrome (HPS) in the United States between 4 June 1993 and 1 September 1994. Therapy was initiated prior to laboratory confirmation of hantavirus infection because most deaths from HPS occur within 48 h of hospitalization. Thirty patients with confirmed HPS, 105 patients without HPS and 5 patients without adequate diagnostic testing for HPS were enrolled. This observational study arguably provides the most complete information available on ribavirin-associated adverse effects. Although ribavirin was generally well tolerated, 71% of recipients became anaemic and 19% underwent transfusion. An apparent excess of hyperamylasaemia/pancreatitis was either therapy-associated or due to enrollment bias. The 30 enrolled HPS patients had a case-fatality rate of 47% (14/30). It is not possible to assess efficacy with this study design. However, comparison of survival curves for the 30 enrolled HPS patients and 34 patients who developed HPS during the same time period but were not enrolled did not suggest an appreciable drug effect. A randomized, placebo-controlled trial that enrolls patients during the prodrome phase would be necessary to assess the efficacy and further define the safety of intravenous ribavirin for HPS.

Hantavirus pulmonary syndrome in Florida: association with the newly identified Black Creek Canal virus.

Hantavirus pulmonary syndrome (HPS) is a recently recognized viral zoonosis. The first recognized cases were caused by a newly described hantavirus. Sin Nombre virus (previously known as Muerto Canyon virus), isolated from Peromyscus maniculatus (deer mouse). We describe a 33-year-old Floridian man who resided outside the ecologic range of P maniculatus but was found to have serologic evidence of a hantavirus infection during evaluation of azotemia associated with adult respiratory distress syndrome. Small mammal trapping conducted around this patient's residence demonstrated the presence of antihantaviral antibodies in 13% of Sigmodon hispidus [cotton rat). Serologic testing using antigen derived from the Black Creek Canal hantavirus subsequently isolated from this rodent established that this patient was acutely infected with this new pathogenic American hantavirus. HPS is not confined to the geographical distribution of P maniculatus and should be suspected in individuals with febrile respiratory syndromes, perhaps associated with azotemia, throughout the continental United States.

Characterization of Langat virus antigenic determinants defined by monoclonal antibodies to E, NS1 and preM and identification of a protective, non-neutralizing preM-specific monoclonal antibody.

Hybridomas secreting monoclonal antibodies (MAb) to the tick-borne encephalitis (TBE) group virus, Langat virus (LGTV), were prepared. Of more than 200 MAb screened, 19 antibodies, which cross-reacted with the etiologic agent of Central European encephalitis, were selected for further characterization. Of these MAb, 15 were specific for LGTV E glycoprotein, two for the NS1 protein, and three for preM protein. The two NS1-specific MAb and two of the E-specific MAb reacted with all six of the other TBE group viruses tested while the remainder of the E-specific MAb failed to recognize at least one of the viruses. None of the MAb neutralized LGTV in cell culture assays, but one of the preM-specific MAb protected weanling mice against a virulent LGTV challenge. Although protective antibodies to E and NS1 proteins of TBE viruses were reported, our data provided the first evidence for protection by a non-neutralizing antibody to the preM or M protein of any of the tick-borne flaviviruses.

Utilization of autopsy RNA for the synthesis of the nucleocapsid antigen of a newly recognized virus associated with hantavirus pulmonary syndrome.

A newly recognized hantavirus was recently found to be associated with an outbreak of acute respiratory illness in the southwestern United States. The disease, which has become known as hantavirus pulmonary syndrome, has an unusually high mortality (64%). Virus isolation attempts have been unsuccessful thus far, resulting in a lack of homologous antigen for use in diagnostic assays. For this reason, a molecular approach was initiated to produce recombinant homologous antigen. The virus nucleocapsid (N) protein was selected, since N has been shown to be a sensitive antigenic target in other hantavirus systems. The N protein open reading frame of the virus S genome segment was synthesized from frozen autopsy tissue by polymerase chain reaction amplification, followed by cloning and expression in Hela cells (vaccinia-T7 RNA polymerase system) and Escherichia coli. N protein-expressing Hela cells served as excellent antigens for an improved indirect immunofluorescence assay. Use of the E. coli-expressed N protein in an enzyme-linked immunosorbent assay improved the sensitivity and specificity when compared with heterologous antigens used previously. Preliminary analysis also indicates that the higher sensitivity could result in earlier detection of infected persons. These data demonstrate that even in the absence of a virus isolate, the necessary homologous antigen can be produced and can serve to improve the detection and diagnostic capabilities needed to combat this newly recognized fatal respiratory illness in the United States.

Isolation, characterization and geographic distribution of Caño Delgadito virus, a newly discovered South American hantavirus (family Bunyaviridae).

Rodents collected from the Venezuelan llanos (plains) during field studies of viral hemorrhagic fever were tested for evidence of hantavirus infection. Hantavirus antibody was found in one (7.7%) of 13 Oryzomys bicolor, one (3.4%) of 29 Rattus rattus, 10 (6.0%) of 166 Sigmodon alstoni and one (2.2%) of 45 Zygodontomys brevicauda. Hantavirus-specific RNA was detected in lung tissues from four antibody-positive rodents: two S. alstoni from Portuguesa State and one S. alstoni each from Cojedes and Barinas States. A hantavirus isolate (herein identified as VHV-574) was recovered from lung tissue from a hantavirus RNA-positive S. alstoni collected from Portuguesa State. The results of serological tests and analyses of small and medium RNA segment nucleotide sequence data indicated that VHV-574 represents a novel hantavirus (proposed name 'Caño Delgadito') that is distinct from all previously characterized hantaviruses. The results of analyses of nucleotide sequence data from the four hantavirus RNA-positive S. alstoni suggested that Caño Delgadito virus is widely distributed in the Venezuelan llanos.

Nipah virus infection among abattoir workers in Malaysia, 1998-1999.

BACKGROUND: An outbreak of encephalitis primarily affecting pig farmers occurred during 1998-1999 in Malaysia and was linked to a new paramyxovirus, Nipah virus, which infected pigs, humans, dogs, and cats. Because five abattoir workers were also affected, a survey was conducted to assess the risk of Nipah infection among abattoir workers. METHODS: Workers from all 143 registered abattoirs in 11 of 13 states in Malaysia were invited to participate in this cross-sectional study. Participants were interviewed to ascertain information on illness and activities performed at the abattoir. A serum sample was obtained to test for Nipah virus antibody. RESULTS: Seven (1.6 %) of 435 abattoir workers who slaughtered pigs versus zero (0%) of 233 workers who slaughtered ruminants showed antibody to Nipah virus (P = 0.05). All antibody-positive workers were from abattoirs in the three states that reported outbreak cases among pig farmers. Workers in these three states were more likely than those in other states to have Nipah antibody (7/144 [4.86%] versus 0/291 [0%], P < 0.001) and report symptoms suggestive of Nipah disease in pigs admitted to the abattoirs (P = 0.001). CONCLUSIONS: Nipah infection was not widespread among abattoir workers in Malaysia and was linked to exposure to pigs. Since it may be difficult to identify Nipah-infected pigs capable of transmitting virus by clinical symptoms, using personal protective equipment, conducting surveillance for Nipah infection on pig farms which supply abattoirs, and avoiding handling and processing of potentially infected pigs are presently the best strategies to prevent transmission of Nipah virus in abattoirs.

Management of a Sabiá virus-infected patients in a US hospital.

OBJECTIVE: To describe the hospital precautions used to isolate a Sabiá virus (arenavirus: Arenaviridae)-infected patient in a US hospital and to protect hospital staff and visitors. DESIGN: Investigation of a single case of arenavirus laboratory-acquired infection and associated case-contacts. SETTING: A 900-bed, tertiary-care, university-affiliated medical center. PATIENTS OR OTHER PARTICIPANTS: The case-patient became ill with Sabiá virus infection. The case-contacts consisted of healthcare workers, coworkers, friends, and relatives of the case-patient. INTERVENTION: Enhanced isolation precautions for treatment of a viral hemorrhagic fever (VHF) patient were implemented in the clinical laboratory and patient-care setting to prevent nosocomial transmission. The enhanced precautions included preventing aerosol spread of the virus from the patient or his clinical specimens. All case-contacts were tested for Sabiá virus antibodies and monitored for signs and symptoms of early disease. RESULTS: No cases of secondary infection occurred among 142 case-contacts. CONCLUSIONS: With the frequency of worldwide travel, patients with VHF can be admitted to a local hospital at any time in the United States. The use of enhanced isolation precautions for VHF appeared to be effective in preventing secondary cases by limiting the number of contacts and promoting proper handling of laboratory specimens. Patients with VHF can be managed safely in a local hospital setting, provided that appropriate precautions are planned and implemented.

Experimental infection of cynomolgus macaques with Ebola-Reston filoviruses from the 1989-1990 U.S. epizootic.

This study describes the pathogenesis of the Ebola-Reston (EBO-R) subtype of Ebola virus for experimentally infected cynomolgus monkeys. The disease course of EBO-R in macaques was very similar to human disease and to experimental diseases in macaques following EBO-Zaire and EBO-Sudan infections. Cynomolgus monkeys infected with EBO-R in this experiment developed anorexia, occasional nasal discharge, and splenomegaly, petechial facial hemorrhages and severe subcutaneous hemorrhages in venipuncture sites, similar to human Ebola fever. Five of the six EBO-R infected monkeys died, 8 to 14 days after inoculation. One survived and developed high titered neutralizing antibodies specific for EBO-R. The five acutely ill monkeys shed infectious virus in various bodily secretions. Further, abundant virus was visualized in alveolar interstitial cells and free in the alveoli suggesting the potential for generating infectious aerosols. Thus, taking precautions against aerosol exposures to filovirus infected primates, including humans, seems prudent. This experiment demonstrated that EBO-R was lethal for macaques and was capable of initiating and sustaining the monkey epizootic. Further investigation of this animal model should facilitate development of effective immunization, treatment, and control strategies for Ebola hemorrhagic fever.

Viremia and antibody response to La Crosse virus in sentinel gray squirrels (Sciuris carolinensis) and chipmunks Tamias striatus).

Six isolates of La Crosse (LAC) virus were obtained from sentinel gray squirrels (Sciuris carolinensis) and four from sentinel chipmunks (Tamias striatus) in an endemic area. Viremia titers were measured by plaquing on Vero cells. Antibody responses of the animals were measured by a microneutralization test employing four California group viruses: LAC, snowshoe hare (SSH), trivittatus, and Jamestown Canyon. In both species LAC antibody titers peaked at approximately 21 days and were still detectable in all animals at 256 days post-viremia. In chipmunks, homologous LAC virus antibody levels were consistently higher than heterologous antibody responses throughout the period recorded. However, in squirrels, homologous LAC virus and heterologous SSH virus antibody responses were initially comparable. This heterologous SSH titer rapidly declined while LAC antibody levels remained relatively high. Data indicate that antibody response persists from one summer season to the next. Viremia titers in both species indicate that these two species are capable of infecting Aedes triseriatus, the principal vector of LAC virus. This is the first reported field isolation of LAC virus from the squirrel.

Antibodies to hemorrhagic fever viruses in domestic livestock in Niger: Rift Valley fever and Crimean-Congo hemorrhagic fever.

A repository of domestic animal sera collected in Niger between 1984 and 1988 was assayed for antibody against two zoonotic hemorrhagic fever viruses known to be present in the West African Sahel. A total of 2,540 serum samples from 2,324 cattle, sheep, goats, and camels were tested by an IgG-specific enzyme-linked immunosorbent assay (ELISA) and the 80% plaque reduction neutralization test (PRNT80) for Rift Valley fever (RVF) virus antibody. Of the 2,540 sera tested for RVF-specific IgG antibody, 1,676 sera from cattle, sheep, and goats were examined for RVF-specific IgM antibody by ELISA. A subset of 2,263 sera were examined for evidence of Crimean-Congo hemorrhagic fever (CCHF) virus antibody by an IgG-specific ELISA. Antibody against CCHF virus was found to be most prevalent in adult cattle (422 of 732 or 57.7% positive) sampled at nine locations in the Niamey area. The highest prevalence for RVF neutralizing antibodies was found in camels from the Agadez Department with 67 (47.5%) of 141 positive. The results indicate that both CCHF and RVF viruses are circulating in Niger and are potential zoonotic health risks.

Effect of normal mosquito extracts upon arbovirus recoveries from mosquito pools.

Titers of Turlock (TUR) and Hart Park (HP) viruses were reduced to undetectable levels when virus was mixed with a triturated suspension of uninfected (normal) 4th instar larvae of Culex tarsalis prior to plaque assay in cell culture. There was a linear relationship between the number of larvae in the pool and the titer of virus recoverable. Virus was undetectable when 1,000-10,000 PFU of either agent was added to pools that contained 25 or more larvae. Suspensions of up to 25 adult male or female Cx. tarsalis had little effect on detectable viral titers while pupal suspensions had an intermediate effect. The inhibitory effect of normal larval extracts on viral infectivity could be counteracted by use of polycations or a high pH buffer. A similar reduction in titer of TUR virus was observed with extracts of larvae of Aedes melanimon or Anopheles franciscanus. Larval extracts of Cx. tarsalis similarly reduced titers of California and St. Louis encephalitis viruses but not western equine encephalomyelitis virus. These findings may have significant bearing on the interpretation of transovarial transmission attempts in which pooled larvae are assayed for virus.

Outbreak of hemorrhagic fever with renal syndrome among U.S. Marines in Korea.

Fourteen of 3,754 U.S. Marines who participated in a joint United States-Republic of Korea training exercise during the autumn of 1986 developed hemorrhagic fever with renal syndrome (HFRS). Clinical and laboratory findings among cases included fever, headache, fatigue, gastrointestinal dysfunction, thrombocytopenia, and proteinuria. Ten individuals were hospitalized; 2 died. No subclinical infections were identified through a post-deployment screen of sera obtained from 2,053 exercise participants. Analysis of questionnaires identified no environmental, occupational, or temporal factors as risks for developing disease. However, 13 of the 14 cases occurred among individuals housed at 1 of the 2 base camps used during the exercise. This outbreak represents the largest cluster of HFRS cases among U.S. personnel in the Republic of Korea since the Korean conflict.

Lymphocytic choriomeningitis virus infection and house mouse (Mus musculus) distribution in urban Baltimore.

Four hundred eighty house mice (Mus musculus) were trapped primarily from urban sites in Baltimore, Maryland from 1984 to 1989 and tested for antibody to lymphocytic choriomeningitis virus (LCMV). The majority of mice (95%) were trapped in residences at two city locations (n = 260), or in an urban park (n = 196); five additional sites were sampled. Overall, 9.0% of the mice were LCMV antibody positive and infected animals were obtained from six of eight sites, including all three of the primary city sites, where the prevalence varied significantly (3.9-13.4%). The location with the highest prevalence was an inner city residential site where positive mice were found significantly clustered within blocks and households. In this location, LCMV antibody prevalence was also significantly correlated with estimates of mouse density within individual blocks. The focal nature of LCMV infection in house mice may result from contact or vertical transmission of virus in conjunction with the highly structured social system of mice, which promotes inbreeding and limited dispersal.