Clarence J. Peters

Hantavirus Pulmonary Syndrome: A Clinical Description of 17 Patients with a Newly Recognized Disease

Background In May 1993 an outbreak of severe respiratory illness occurred in the southwestern United States. A previously unknown hantavirus was identified as the cause. In Asia hantaviruses are associated with hemorrhagic fever and renal disease. They have not been known as a cause of human disease in North America. Methods We analyzed clinical, laboratory, and autopsy data on the first 17 persons with confirmed infection from this newly recognized strain of hantavirus. Results The mean age of the patients was 32.2 years (range, 13 to 64); 61 percent were women, 72 percent were Native American, 22 percent white, and 6 percent Hispanic. The most common prodromal symptoms were fever and myalgia (100 percent), cough or dyspnea (76 percent), gastrointestinal symptoms (76 percent), and headache (71 percent). The most common physical findings were tachypnea (100 percent), tachycardia (94 percent), and hypotension (50 percent). The laboratory findings included leukocytosis (median peak cell count, 26,000 per cu...

Ebola Hemorrhagic Fever in Kikwit, Democratic Republic of the Congo: Clinical Observations in 103 Patients

During the 1995 outbreak of Ebola hemorrhagic fever in the Democratic Republic of the Congo, a series of 103 cases (one-third of the total number of cases) had clinical symptoms and signs accurately recorded by medical workers, mainly in the setting of the urban hospital in Kikwit. Clinical diagnosis was confirmed retrospectively in cases for which serum samples were available (n = 63, 61% of the cases). The disease began unspecifically with fever, asthenia, diarrhea, headaches, myalgia, arthralgia, vomiting, and abdominal pain. Early inconsistent signs and symptoms included conjunctival injection, sore throat, and rash. Overall, bleeding signs were observed in <45% of the cases. Typically, terminally ill patients presented with obtundation, anuria, shock, tachypnea, and normothermia. Late manifestations, most frequently arthralgia and ocular diseases, occurred in convalescent patients. This series is the most extensive number of cases of Ebola hemorrhagic fever observed during an outbreak.

Preliminary report: isolation of Ebola virus from monkeys imported to USA

An epizootic caused by an Ebola-related filovirus and by simian haemorrhagic fever virus began among cynomolgus monkeys in a US quarantine facility after introduction of monkeys from the Philippines. This incident, the first in which a filovirus has been isolated from non-human primates without deliberate infection, raises the possibility that cynomolgus monkeys could be a reservoir of Ebola virus infection.

Clinical, Virologic, and Immunologic Follow-Up of Convalescent Ebola Hemorrhagic Fever Patients and Their Household Contacts, Kikwit, Democratic Republic of the Congo

A cohort of convalescent Ebola hemorrhagic fever (EHF) patients and their household contacts (HHCs) were studied prospectively to determine if convalescent body fluids contain Ebola virus and if secondary transmission occurs during convalescence. Twenty-nine EHF convalescents and 152 HHCs were monitored for up to 21 months. Blood specimens were obtained and symptom information was collected from convalescents and their HHCs; other body fluid specimens were also obtained from convalescents. Arthralgias and myalgia were reported significantly more often by convalescents than HHCs. Evidence of Ebola virus was detected by reverse transcription-polymerase chain reaction in semen specimens up to 91 days after disease onset; however, these and all other non-blood body fluids tested negative by virus isolation. Among 81 initially antibody negative HHCs, none became antibody positive. Blood specimens of 5 HHCs not identified as EHF patients were initially antibody positive. No direct evidence of convalescent-to-HHC transmission of EHF was found, although the semen of convalescents may be infectious. The existence of initially antibody-positive HHCs suggests that mild cases of Ebola virus infection occurred and that the full extent of the EHF epidemic was probably underestimated.

Evaluation of Immune Globulin and Recombinant Interferon-α2b for Treatment of Experimental Ebola Virus Infections

A passive immunization strategy for treating Ebola virus infections was evaluated using BALB/ c mice, strain 13 guinea pigs, and cynomolgus monkeys. Guinea pigs were completely protected by injection of hyperimmune equine IgG when treatment was initiated early but not after viremia had developed. In contrast, mice were incompletely protected even when treatment was initiated on day 0, the day of virus inoculation. In monkeys treated with one dose of IgG on day 0, onset of illness and viremia was delayed, but all treated animals died. A second dose of IgG on day 5 had no additional beneficial effect. Pretreatment of monkeys delayed onset of viremia and delayed death several additional days. Interferon-alpha2b (2 x 10(7) IU/kg/day) had a similar effect in monkeys, delaying viremia and death by only several days. Effective treatment of Ebola infections may require a combination of drugs that inhibit viral replication in monocyte/macrophage-like cells while reversing the pathologic effects (e.g., coagulopathy) consequent to this replication.

Markedly Elevated Levels of Interferon (IFN)-γ, IFN-α, Interleukin (IL)-2, IL-10, and Tumor Necrosis Factor-α Associated with Fatal Ebola Virus Infection

The role of immune mechanisms in the pathogenesis of Ebola hemorrhagic fever (EHF) remains to be elucidated. In this report, the serum cytokine levels of patients who died of EHF were compared with those of patients who recovered and those of control patients. A marked elevation of interferon (IFN)-gamma levels (>100 pg/mL) was observed in sequential serum samples from all fatal EHF cases compared with patients who recovered or controls. Markedly elevated serum levels of interleukin (IL)-2, IL-10, tumor necrosis factor (TNF)-alpha, and IFN-alpha were also noted in fatal EHF cases; however, they had a greater degree of variability. No differences were noted in serum levels of IL-4 and IL-6. mRNA quantitation from blood clots of the same patients showed relatively elevated levels of TNF-alpha and IFN-alpha in samples from EHF patients. Taken together, these results suggest that a high degree of immune activation accompanies and potentially contributes to a fatal outcome in EHF patients.

An Outbreak of Rift Valley Fever in Northeastern Kenya, 1997-98

In December 1997, 170 hemorrhagic fever-associated deaths were reported in Carissa District, Kenya. Laboratory testing identified evidence of acute Rift Valley fever virus (RVFV). Of the 171 persons enrolled in a cross-sectional study, 31(18%) were anti-RVFV immunoglobulin (Ig) M positive. An age-adjusted IgM antibody prevalence of 14% was estimated for the district. We estimate approximately 27,500 infections occurred in Garissa District, making this the largest recorded outbreak of RVFV in East Africa. In multivariate analysis, contact with sheep body fluids and sheltering livestock in one’s home were significantly associated with infection. Direct contact with animals, particularly contact with sheep body fluids, was the most important modifiable risk factor for RVFV infection. Public education during epizootics may reduce human illness and deaths associated with future outbreaks.

Persistence and Genetic Stability of Ebola Virus during the Outbreak in Kikwit, Democratic Republic of the Congo, 1995

Ebola virus persistence was examined in body fluids from 12 convalescent patients by virus isolation and reverse transcription-polymerase chain reaction (RT-PCR) during the 1995 Ebola hemorrhagic fever outbreak in Kikwit, Democratic Republic of the Congo. Virus RNA could be detected for up to 33 days in vaginal, rectal, and conjunctival swabs of 1 patient and up to 101 days in the seminal fluid of 4 patients. Infectious virus was detected in 1 seminal fluid sample obtained 82 days after disease onset. Sequence analysis of an RT-PCR fragment of the most variable region of the glycoprotein gene amplified from 9 patients revealed no nucleotide changes. The patient samples were selected so that they would include some from a suspected line of transmission with at least three human-to-human passages, some from 5 survivors and 4 deceased patients, and 2 from patients who provided multiple samples through convalescence. There was no evidence of different virus variants cocirculating during the outbreak or of genetic variation accumulating during human-to-human passage or during prolonged persistence in individual patients.

ELISA for the Detection of Antibodies to Ebola Viruses

EIAs for IgG and IgM antibodies directed against Ebola (EBO) viral antigens have been developed and evaluated using sera of animals and humans surviving infection with EBO viruses. The IgM capture assay detected anti-EBO (subtype Reston) antibodies in the sera of 5 of 5 experimentally infected animals at the time they succumbed to lethal infections. IgM antibodies were also detected in the serum of a human who was infected with EBO (subtype Reston) during a postmortem examination of an infected monkey. The antibody was detectable as early as day 6 after infection in experimentally infected animals and persisted for <90 days. The IgG response was less rapid; however, it persisted for >400 days in 3 animals who survived infection, and it persisted for approximately 10 years after infection in the sera of 2 humans. Although these data are limited by the number of sera available for verification, the IgM assay seems to have great promise as a diagnostic tool. Furthermore the long-term persistence of the IgG antibodies measured by this test strongly suggests that the ELISA will be useful in field investigations of EBO virus.

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.