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Emerging Infectious Diseases

ISSN: 1080-6059

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The = Case=20
Dispatch=20
Acknowledgment= s=20
References= =20
Table=20
Appendix Table=20
Suggested=20 Citation

EID Journal=20 Home > Volume = 16,=20 Number 10=96October 2010

Volume 16, Number 10=96October 2010

Dispatch

Imported Lassa Fever, Pennsylvania, USA, 2010

Valerianna Amorosa , Adam MacNeil, Ryan McConnell, Ami Patel, = Katherine E.=20 Dillon, Keith Hamilton, Bobbie Rae Erickson, Shelley Campbell, Barbara = Knust,=20 Deborah Cannon, David Miller, Craig Manning, Pierre E. Rollin, and = Stuart T.=20 Nichol
Author affiliations: University of Pennsylvania,=20 Philadelphia, Pennsylvania, USA (V. Amorosa, R. McConnell, K.E. Dillon, = K.=20 Hamilton); Philadelphia Veterans Affairs Medical Center, Philadelphia = (V.=20 Amorosa); Centers for Disease Control and Prevention, Atlanta, Georgia, = USA (A.=20 MacNeil, A. Patel, B.R. Erickson, S. Campbell, B. Knust, D. Cannon, D. = Miller,=20 C. Manning, P.E. Rollin, S.T. Nichol); and Philadelphia Department of = Health,=20 Philadelphia (A. Patel)

Suggested=20 citation for this article

Abstract
We report a case of Lassa fever in a US = traveler=20 who visited rural Liberia, became ill while in country, sought medical = care upon=20 return to the United States, and subsequently had his illness laboratory = confirmed. The patient recovered with supportive therapy. No secondary = cases=20 occurred.

Lassa fever is a potentially severe viral infection caused = by Lassa=20 virus (family Arenaviridae,=20 genus Arenavirus), with an overall case-fatality rate of = 1%=962% and=20 a case-fatality rate of 15%=9620% for hospitalized patients (1,2). = The virus=20 is endemic to West Africa, with the reservoir host=20 being Mastomys spp. rodents (3).=20 Person-to-person transmission of Lassa virus can occur through direct = exposure=20 to infected blood or secretions, and instances of nosocomial = transmission have=20 been documented (4,5). = Primary=20 symptoms of Lassa fever are fever, headache, nausea, diarrhea, sore = throat, and=20 myalgia; hemorrhagic signs or deafness may also occur during illness = (1,6).

Because the incubation period ranges from a few days to >2 weeks = (1,5) = and many=20 symptoms are nonspecific, the potential exists for human carriage of = Lassa virus=20 to areas outside those to which it is endemic, putting travel = companions, close=20 contacts, and healthcare providers at risk for secondary infection. = Before 2010,=20 five instances of imported Lassa virus were recorded in persons from = West Africa=20 to the United States. Although early instances involved sick persons who = were=20 airlifted to the United States for diagnosis and treatment (7=969),= the 2 most=20 recent occurrences (1989 and 2004) involved persons who were not = identified as=20 potentially infectious until healthcare was sought in the United States = (10,11). = Here we=20 report a case in a person who became infected and sick during a trip to = Liberia=20 and sought care upon return to the United States.

The Case

A Liberian man 47 years of age living in the United States traveled = to=20 Liberia in January 2010. He arrived in Monrovia, then spent 5 days = traveling=20 throughout Nimba County in north-central Liberia, bordering Guinea and = C=F4te=20 d=92Ivoire. He reported sleeping nightly in his rural native village in = a dwelling=20 infested with rats and recalled several rat carcasses on the bedroom = floor. On=20 the day of his departure from Liberia, he developed fever, chills, joint = pain of=20 the knees and ankles, anorexia, sore throat, diffuse skin tenderness, = and mild=20 shortness of breath; he began taking amoxicillin and chloroquine before=20 departing Liberia.

The patient=92s symptoms persisted upon arrival in the United States, = prompting=20 him to seek medical attention on day 5 of his illness. When he sought = treatment,=20 he had fever of 103=B0F, pulse of 99 beats/min, respiratory rate of 15=20 breaths/min, and blood pressure of 120/80 mm Hg (Appendix Table). His physical examination was = notable=20 for posterior cervical adenopathy and a palpable spleen tip (Table). He had no evidence of conjunctival, = nasal, or=20 oral petechiae; no skin rashes; and no signs of hemorrhage or other = lesions.=20 Initial laboratory data showed leukopenia and thrombocytopenia and = minimal=20 transaminase elevations (Appendix Table). Empiric malaria treatment = was=20 initiated upon admission and was subsequently discontinued=20 when Plasmodium spp. antigen testing was negative and = thick=20 and thin blood smears showed no evident parasitemia. By the next day, = mild=20 pharyngitis with slight tonsillar exudates had developed. On the third = hospital=20 day, substernal chest pain and profuse watery diarrhea developed. = Increasing=20 transaminases and a slight coagulopathy were noted. Lassa fever was = considered=20 in the differential diagnosis; contact precautions and, subsequently, = airborne=20 precautions were taken. Because of noted clinical improvement, he was = not given=20 empiric intravenous ribavirin.

On day 5 of hospitalization, Lassa virus was identified by real-time = PCR by=20 using samples collected 2 days earlier, and sequencing of the amplified = fragment=20 yielded a unique sequence similar to sequences from previous Lassa virus = isolates from Liberia. Subsequent samples confirmed Lassa fever = diagnosis on the=20 basis of real-time PCR, viral culture, and serology (Table).

The patient=92s fever resolved by day 16 of his illness. After 2 = successive=20 negative blood real-time PCR results, he was discharged from the = hospital on day=20 21 of his illness with instructions to avoid unprotected sexual = intercourse for=20 2 months. No hearing abnormalities were noted at the time of discharge = or during=20 telephone conversations 2 weeks and 2 months later.

A contact investigation was undertaken by the hospital and local, = state,=20 federal, and international health agencies. Exposed persons were = identified as=20 any persons who potentially came into contact with the patient or his = body=20 fluids during his illness. Because no contacts had direct exposure to = body=20 fluids (other than the patient=92s wife in Africa with whom he had = sexual=20 intercourse before becoming ill and who remained well, according to = telephone=20 follow-up with the patient), no patient contacts were considered high = risk for=20 secondary transmission (10). = In total,=20 140 persons, including the patient=92s family in the United States, = co-workers,=20 and hospital workers who had contact with him (but did not have direct = contact=20 with bodily fluids) were identified as low-risk contacts. Health = communication=20 materials were developed on the basis of previous Lassa fever contact = tracing=20 activities (10). = All=20 hospital and community contacts were provided a Lassa fever fact sheet = and asked=20 to seek medical consultation if fever or other signs and symptoms of = Lassa fever=20 appeared. Upon completion of 21 days of follow-up, no secondary cases = were=20 identified.

Conclusions

The spectrum of Lassa fever can run from asymptomatic seroconversion = to=20 severe hemorrhagic fever with multiple organ failure and death (1,2,6).= Factors=20 supporting the diagnosis of Lassa fever in returning travelers include = relevant=20 epidemiologic exposure (travel to rural West Africa), signs and symptoms = consistent with Lassa fever, and the absence of other infectious agents = that can=20 account for the illness. Although this patient did not seek treatment = for=20 hemorrhagic signs, his fever, pharyngitis, chest pain, and diarrhea = (1,6), = as well as=20 thrombocytopenia and elevated transaminases, were consistent with Lassa = fever=20 (6,12). = Early=20 institution of ribavirin can dramatically decrease death rates among = patients=20 with severe Lassa fever if given within the first 6 days of illness = (12); = therefore,=20 empiric ribavirin should be considered for an ill patient suspected of = having=20 Lassa fever.

As in this case, early suspicion of Lassa fever should prompt = isolation=20 measures to avoid secondary transmission; laboratory testing should be = limited=20 to essential tests, and all laboratory specimens should be handled with=20 appropriate biosafety precautions to avoid aerosolizing the virus = (13). = Experience=20 in regions where Lassa virus is endemic suggests human-to-human = transmission=20 occurs through direct contact with blood and body fluids or = large-particle=20 inhalation; transmission through viral aerosolization is not seen; and=20 generally, when universal precautions are undertaken, transmission is = unlikely=20 (14).=20 Nonetheless, aerosol in addition to contact precautions were undertaken = once=20 Lassa fever was suspected, given the theoretical potential for acquiring = infection through inhalation of airborne virus from respiratory = secretions or,=20 in this case, copious diarrhea.

The patient described in this report represents the sixth known = occurrence of=20 Lassa fever imported to the United States. Clinicians treating recent = travelers=20 to West Africa who are febrile should obtain detailed histories from = patients to=20 determine whether they have traveled into rural areas in which the = potential for=20 exposure to rodents exists. The symptoms, signs, and laboratory = abnormalities of=20 Lassa fever are nonspecific and can overlap with other tropical = infections.=20 Therefore, efforts should be made to promptly diagnose or rule out other = infectious agents in a patient who has the appropriate travel and = exposure=20 history so that further diagnostic studies and empiric therapy with = ribavirin=20 can be undertaken rapidly. Moreover, as soon as Lassa fever is = suspected,=20 patients and their specimens should be handled with adequate = precautions, the=20 local health department and Centers for Disease Control and Prevention = should be=20 notified, and specimens should be sent for specific diagnostic = testing.

Acknowledgments

We thank medical staff, local and state public health personnel, = and the=20 staff of the Centers for Disease Control and Prevention who assisted = with this=20 investigation.

Dr Amorosa is assistant professor of clinical medicine at the = University of=20 Pennsylvania and chief of infectious diseases at the Philadelphia = Veterans=20 Affairs Medical Center. Her research interests include HIV/hepatitis C = co-infection.

References

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Tables

Table. Day by day symptoms and = clinical=20 information for a man 47 years of age with Lassa fever, Pennsylvania, = USA,=20 2010*
Appendix Table. Timeline of = illness for a=20 patient with Lassa fever, Pennsylvania, USA, 2010