Fatal Hemorrhagic Fever Caused by West Nile Virus in the United States

Viral Infections of the Lung

The lungs are among the most vulnerable to microbial assault of all organs in the body. From a contemporary vantage, lower respiratory tract infections are the greatest cause of infection-related mortality in the United States, and rank seventh among all causes of deaths in the United States.2,3 From a global and historic perspective, the scope and scale of lower respiratory tract infection is greater than any other infectious syndrome, and viral pneumonias have proven to be some of the most lethal and dramatic of human diseases. The 1918–1919 influenza pandemic, perhaps the most devastating infectious disease pandemic in recorded history, resulted in an estimated 40 million deaths worldwide, including 700,000 deaths in the U.S.4 The global outbreak of severe acute respiratory syndrome (SARS) during 2003, although considerably smaller in scale, resulted in 8098 cases and 774 deaths5 and is a dramatic contemporary example of the ability of viral pneumonias to rapidly disseminate and cause severe disease in human populations.

Fatal multiorgan failure due to yellow fever vaccine-associated viscerotropic disease

Yellow fever vaccine-associated viscerotropic disease (YEL-AVD) is a rare complication of yellow fever (YF) vaccination. A previously healthy 22-year-old female died following YF vaccination despite aggressive measures. Serial viral load titers, cytokine levels and host genetic factors were evaluated in an attempt to understand this unusual and lethal outcome. The patient's high-titer vaccine viremia and possibly related minor genetic anomalies provide clues to exploring the etiology of YEL-AVD.

West Nile encephalitis, status epilepticus and West Nile pneumonia in a renal transplant patient

West Nile neuroinvasive disease (WNND) represents a small fraction of cases of West Nile Virus (WNV) infection. Organ transplantation is associated with increased risk of acquiring WNND. We report a patient with living-related renal transplantation who developed unusual manifestations of WNND. First, fatal status epilepticus unresponsive to pentobarbital ensued. Status epilepticus from WNV has been described very rarely in the medical literature. Second, this patient grew WNV on broncho-alveolar lavage samples. To our knowledge, this is the first case of culture positive West Nile pneumonia. Third, the finding in cerebrospinal fluid (CSF) of a negative West Nile immunoglobulin M (IgM) and a positive West Nile polymerase chain reaction is striking. It is consistent with a high-viral burden and impaired immune response. This finding raises questions about the appropriateness of relying on CSF IgM assays to rapidly diagnose WNV encephalitis in organ transplant patients, as has been recommended.

Systemic distribution of West Nile virus infection: postmortem immunohistochemical study of six cases

Rare cases of West Nile virus (WNV)-associated inflammation outside the central nervous system (CNS) have been reported. We evaluated the systemic distribution of WNV in postmortem tissues during encephalitis in six patients using immunohistochemistry. WNV antigens were detected in neurons of CNS (all 6 cases), kidney (4 cases), lungs (2 cases), pancreas (2 cases), thyroid (2 cases), intestine (2 cases), stomach (1 case), esophagus (1 case), bile duct (1 case), skin (1 case), prostate (1 case) and testis (1 case). In systemic organs epithelial cells were infected. In none of the six cases were viral antigens identified in hepatocytes, heart, adrenal gland, nerves, skeletal muscles, bone, vessels and fat. All cases in which viral antigens were identified in systemic organs in addition to CNS were severely immunocompromised transplant recipients. With the exception of testis and brain, most foci of infection were not associated with inflammation. While the absence of inflammation may in part be due to patient immunosuppression or to possible transient nature of any host response, compartmentalization of viral antigen to the luminal region of epithelial cells may sequester WNV from immune recognition. Comparison of our findings with previous reports suggests that patients with WNV encephalitis can have widespread systemic infection.

Clinical findings, lesions, and viral antigen distribution in great gray owls (Strix nebulosa) and barred owls (Strix varia) with spontaneous West Nile virus infection

West Nile Virus (WNV) infection manifests itself clinically a nd pathologically differently in various species of birds. The clinicopathologic findings and WNV antigen tissue distribution of six great gray owls (Strix nebulosa) and two barred owls (Strix varia) with WNV infection are described in this report. Great gray owls usually live in northern Canada, whereas the phylogenetically related barred owls are native to the midwestern and eastern United States and southern Canada. Naturally acquired WNV infection caused death essentially without previous signs of disease in the six great gray owls during a mortality event. Lesions of WNV infection we re dominated by hepatic and splenic necrosis, with evidence o f disseminatedintravascular coagulation in the great gray owls. WNV antigen was widely distributed in th e organs of the great gray owls and appeared totarget endothelial cells, macrophages, and hepatocytes. The barred owls represented two sporadic cases. They had neurologic disease with mental dullness that led to euthanasia. These birds had mild to moderate lymphoplasmacytic encephalitis with glial nodules and lymphoplasmacytic pectenitis. WNV antigen was sparse in barred owls and only present in a few brain neurons and renaltubular epithelial cells. The cause of the different manifestations of WNV disease in these fairly closely related owl species is uncertain.

Detection of West Nile virus in formalin-fixed, paraffin-embedded human tissues by RT-PCR: A useful adjunct to conventional tissue-based diagnostic methods

BACKGROUND

West Nile virus (WNV), a member of genus Flavivirus, causes febrile illness, encephalitis, meningitis, myelitis, and occasional deaths in humans. Although several reverse transcription-polymerase chain reaction (RT-PCR) assays have been developed for detection of WNV in serum, cerebrospinal fluid, and fresh tissues, the usefulness of WNV RT-PCR assays for RNA extracted from formalin-fixed human tissues has not previously been demonstrated.

OBJECTIVE

The objective of this study was to evaluate the application of a RT-PCR technique for the detection of WNV in routinely processed, formalin-fixed, paraffin-embedded (FFPE) human tissues, and to compare it with conventional serology and immunohistochemistry (IHC).

STUDY DESIGN

We performed two WNV-specific nested RT-PCR assays targeting the viral capsid, premembrane, and envelope genes in FFPE central nervous system tissue samples from 27 patients with fatal WNV encephalitis, as confirmed by serology or IHC, and compared the results. The presence of WNV in RT-PCR-positive samples was confirmed by amplicon sequencing.

RESULTS

Twenty (74%) patients were WNV RT-PCR positive while 24 (89%) were seropositive. WNV IHC staining of neurons and neuronal processes was positive in fourteen (52%) patients. The concordance between IHC and serology was 41% (11/27) and between RT-PCR and serology was 63% (17/27). All 11 seropositive/IHC-positive patients and 6 (46%) of 13 seropositive/IHC-negative patients were RT-PCR positive while all 3 seronegatives were positive by both IHC and RT-PCR.

CONCLUSIONS

In this study, RT-PCR was significantly more sensitive than IHC in detecting WNV infections and provided specific sequence information about the infecting virus. RT-PCR on FFPE tissues may be a particularly useful diagnostic tool in patients who die relatively soon after disease onset and for whom serology may be negative. Combined use of serology, IHC, and RT-PCR would be expected to have the best overall sensitivity and improve detection of fatal WNV infection.

West Nile virus: recent trends in diagnosis and vaccine development

West Nile virus (WNV) is a mosquito-borne flavivirus, native to Africa, Europe, and Western Asia. In many respects, WNV is an outstanding example of a zoonotic pathogen that has leaped geographical barriers and can cause severe disease in human and horse. Before the emergence of WNV in the USA, only few methods of diagnosis were available. Recently, many changes in the fields of WN diagnosis and prevention have happened. This paper will review all these new tools. After a description of the main concerns in WNV and West Nile (WN) disease in humans and animals, this review will present the main available tests for serology and virology detection, from gold standard tests to more recently developed methods. Finally, licensed vaccines and candidate vaccines developed in humans, horses and birds will also been described.