West Nile encephalitis epidemic in southeastern Romania

doi:10.1016/S0140-6736(98)03538-7

The Lancet

Volume 352, Issue 9130, 5 September 1998, Pages 767-771

https://doi.org/10.1016/S0140-6736(98)03538-7 Get rights and content

Summary

Background

West Nile fever (WNF) is a mosquito-borne flavivirus infection endemic in Africa and Asia. In 1996, the first major WNF epidemic in Europe occurred in Romania, with a high rate of neurological infections. We investigated the epidemic to characterise transmission patterns in this novel setting and to determine its origin.

Methods

Hospital-based surveillance identified patients admitted with acute aseptic meningitis and encephalitis in 40 Romanian districts, including Bucharest. Infection was confirmed with IgM capture and indirect IgG ELISAs. In October, 1996, we surveyed outpatients in Bucharest and seven other districts to estimate seroprevalence and to detect infected patients not admitted to hospital. We also measured the rates of infection and seropositivity in mosquitoes and birds, respectively.

Results

Between July 15 and Oct 12, we identified 393 patients with serologically confirmed or probable WNF infection, of whom 352 had acute central-nervous-system infections. 17 patients older than 50 years died. Fatality/case ratio and disease incidence increased with age. The outbreak was confined to 14 districts in the lower Danube valley and Bucharest (attack rate 12·4/100 000 people) with a seroprevalence of 4·1%. The number of mild cases could not be estimated. WN virus was recovered from Culex pipiens mosquitoes, the most likely vector, and antibodies to WN virus were found in 41% of domestic fowl.

Interpretation

The epidemic in Bucharest reflected increased regional WNF transmission in 1996. Epidemics of Cx pipiens-borne WNF could occur in other European cities with conditions conducive to transmission.

Introduction

Mosquito-borne West Nile fever (WNF) is an endemic febrile illness in Africa, the Middle East, and southwestern Asia. The flavivirus has also been isolated in Australia and sporadically in Europe but fewer cases in human beings have been recognised. Clinical features are acute fever with severe myalgia, arthralgia, and headache, conjunctivitis, prominent lymphadenopathy, and a roseolar rash, complicated, occasionally, by meningitis or encephalitis.1, 2, 3, 4, 5 Outbreaks with hundreds of cases were reported from Israel in 1950–57. In 1974, an epidemic in a 2500 km² area of central South Africa produced tens of thousands of infections.6, 7 Except for a small outbreak in southern France in 1962, WNF has not been a public-health threat in Europe.⁸ Between July and October, 1996, an epidemic of WNF with mainly neurological infections occurred in Bucharest and the lower Danube valley of southeastern Europe. We described after a field investigation from Sept 28 to Oct 11, 1996, the epidemic, its transmission patterns, and its likely source.

Section snippets

Methods

Romania is divided by the Carpathian range into a region of mountains and high plains to the northwest and a large plain to the south, with the Danube river forming most of the southern border with Bulgaria. Bucharest, the capital city, consists of six administrative sectors and is surrounded by the Ilfov District (figure 1). The national and Bucharest municipal populations were about 23 million and 2·3 million, respectively, in 1996.

In mid-August, 1996, unusually high numbers of acute

Results

Of 835 patients admitted to hospital with suspected central-nervous-system infection and reported under the surveillance system, 767 (92%) met the definition of WNF cases. Appropriate blood, cerebrospinal fluid, and necropsy samples were available from 441 patients, among whom WN encephalitis was serologically confirmed in 352 (80%). In addition, among 68 patients who did not meet the case definition, 41 (60%) had laboratory-confirmed or probable infection. A total of 393 patients had

Discussion

Although WNF is recognised in Africa, Asia, and Europe, encephalitis cases have been reported previously only from Israel, India, and Pakistan.1, 2, 3, 4, 5, 6, 7, 11, 12 Transmission of WN virus in at least 11 European countries (France, Cyprus, former Czechoslovakia, Greece, Italy, Portugal, Romania, Spain, Turkey, former Yugoslavia, and Russia) has been surmised from animal and human serosurveys and by the occasional isolation of the virus from human, horse, wild bird, mosquito (Aedes

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ArticlesWest Nile encephalitis epidemic in southeastern Romania

Summary

Background

Methods

Results

Interpretation

Introduction

Section snippets

Methods

Results

Discussion

Trans Royal Soc Trop Med Hyg

WNF

Geographic spread of Aedes albopictus and potential for involvement in arbovirus cycles in the Mediterranean Basin

J Vector Ecol

A study of the ecology of West Nile virus in Egypt

Am J Trop Med Hyg

The natural history of WNF, I: clinical observations during an epidemic in Israel

Am J Hyg

Isolation of Japanese encephalitis and West Nile viruses from fatal cases of encephalitis in Kolar district of Karnataka

Indian J Med Res

Epidemics of West Nile and Sindbis viruses in South Africa with Culex (Culex) univittatus Theobald as a vector

S Afr J Sci

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Ann Instit Pasteur

A rapid method for detection and identification of flaviviruses by polymerase chain reaction and nucleic acid hybridization

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West Nile virus infection in recent years in Israel

Israel J Med Sci

WNF encephalitis

Israel J Med Sci

Acute pancreatitis in WNF

Am J Trop Med Hyg

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Ann Inst Pasteur

Articles
West Nile encephalitis epidemic in southeastern Romania