VIROLOGY l Fabiyi . LASSA 335

LASSA FEVER () AS A PTJBLTC HF,ALTH PROBLEM1

Akinyele Fabiyi2

Lassa fewer, a disease observed in Africa for the first timein 1969, is highly infectious, Presenting a fiarticular threat to hos#itaL personnel and medical scientists. The recorded out- breaks have had case-fatality rates of from 36 to 67 per cent.

Two “new” have recently been These epidemjcs have had case-fatality rates shown to have caused severe with ranging-from 36 to 67 per cent. high mortality, especially among hospital Lassa fever is characterized by insidious personnel and medical scientists. One of onset with fever, chills, malaise, and aching them, Marburg , is morphologically pains. Its symptoms have been described as unlike any other known virus family.3 The “nonspecific,” and clinical diagnosis can be other has been classified with the arena- entertained only after a number of similar viruses, a group that includes the agent of cases have been observed. Persistently high lymphocytic choriomeningitis and other temperature is usually common in severe or members of the Tacaribe complex, includ- fatal cases. The incubation period of Lassa ing the agents of Argentine and Bolivian fever is from seven to 16 days (average 10). hemorrhagic fever. Pathologically, this is a systemic disease in In 1969 an of undiagnosed in- which many organs and tissues are in- fectious virus disease occurred in northern volved, which probably accounts for the . This was followed a year later by toxic condition of the patient. An infected another epidemic in the same area; 23 person has been shown to shed virus up to 32 patients were hospitalized and 13 died. The days from the development of symptoms. virus isolated from these infections was Some patients who survived Lassa fever named “Lassa fever” virus because the index showed evidence of impaired hearing and case of the 1969 epidemic came from the total nerve deafness. In general the course town of Lassa in the northeast of Nigeria. of Lassa fever resembles that of In Nigeria a total of four epidemics of Lassa and , with which it has been fever have been confirmed-1969, 1970, confused. 1974, and 1975. In other West African Evidence is accumulating to show that countries epidemics have been reported Lassa fever induces premature births and from , in 1972 (Z), and from Sierra abortions in pregnant women. Most preg- Leone, in 1970,1974 (2,3). In addition, nant female patients abort within four days serologic evidence has confirmed existence after admission to hospital; in mild cases, of the disease in and Senegal (2). however, abortion usually takes longer to occur. The question of transplacental infec- tion of the fetus has not been investigated, ‘Working paper, WHO Scientific Group in Virus and so far no attempt has been made to Diseases (Geneva, 1-5 September 1975); also appearing determine whether or not the aborted fe- in Spanish in Bol Of Sanit Panam, 1977. tuses are infected with the virus. ZProfessor and Director, Virus Research Labora- tory, University of Ibadan, Ibadan, Nigeria. In the 1972 epidemic several SSee Dowdle communication above. strains of the virus were isolated from the 336 PAHO BULLETIN . vol. .X, no. 4, 1976

multimammate Mastomys natalensis Recommendations caught in homes of patients (2). Recently other isolations from of the same The following approaches are proposed species caught in several areas of northern in regard to the study and control of Lassa Nigeria (4) have been reported. The fact fever: that these latter isolations have been from l Diagnosis: -Establishment of laboratory diagnos- animals caught in a “nonepidemic” period tic services at local and regional strongly confirms that rodents are reservoirs levels; of the virus. Isolations from rodents other -Special research to develop rapid and than Mastomys have also been reported improved means of diagnosis; and from animals caught in the same general -Provision of a supply of killed virus area of Nigeria (4). antigen and control sera for diag- The mode of transmission from rodents to nosis. man is still not clear. Contamination of l Continuous surveillance: foodstuffs, grains, and water with infected -Checks for individuals with positive feces, , or saliva is suspected. Human Lassa fever virus in the transmission probably occurs from respira- population; tory droplets, urine, or feces. Respiratory -Large-scale banking of positive plas- transmission has been confirmed from the ma for use in epidemics; and following data based on clinical and labora- -Serologic surveys in both endemic tory evidence from epidemics of the disease: and nonendemic areas. 65 per cent of patients have cough, 82 per l Establishment of special laboratory cent have , and 65 per cent have facilities for biochemical (chemical pathol- pulmonary rales; virus has been recovered ogy) and hematologic studies of the disease from the pharynx in 73 per cent of the cases (not the virus). Information in this area (2). Parenteral transmission by accidental may be of value in early diagnosis.

inoculation from infected needles and l Special training of hospital personnel instruments has occurred in a number of (as a task force) specifically to deal with instances. Indirect transmission from han- outbreaks of Lassa fever. There should ulti- dling of contaminated hospital utensils mately be task forces at three levels: local, (bedpans, etc.) can occur, and insect regional, and central (international),

transmission by bites cannot be ruled out. l Establishment of contingency plans at Sera from patients who have recovered all levels with international coordination, from Lassa fever have been shown to have to deal with epidemic outbreaks. high levels of complement-fixing antibody. l Consideration of provision for isolation Persistent CF antibody has been reported centers for the care of Lassa fever patients. more than two years after recovery (3). In l General and basic studies of the addition, silent infections in hospital per- virus(es) for understanding and elucidation sonnel who have had contacts with Lassa of agent-host interactions and for fever patients have been confirmed by development. While this may not be readily demonstration of antibody to the virus. feasible in view of the highly infectious Plasma from recovered Lassa fever patients nature of the virus, some special laboratory, has been used in treatment of the disease. as suggested above, might be allowed to To date five patients have been treated and carry out such studies provided all the only one has died. However, the effective- necessary precautions are undertaken. ness of antibody-positive plasma in the l Eradication of known reservoir hosts treatment of the disease still needs further and other conditions conducive to the main- evaluation. tenance and perpetuation of the disease. VIROLOGY l Kono l ENTEROVIRUSES OTHER THAN POLIOVIRUS 337

Two “new” virus infections, Marburg and propensity. It has also been shown to be the cause Lassa fever, now constitute diseases of public of premature births and spontaneous abortions health importance in several countries of Africa, in pregnant women. The virus is transmitted by especially . Lassa fever has an the respiratory route and by direct contact with insidious onset, is initially difficult to diagnose, contaminated materials. Persistent complement- has “nonspecific” clinical symptoms which have fixing have been demonstrated in been confused with yellow fever and typhoid, patients recovered from the disease. The causa- shows evidence of persistent infection, is tremen- tive agent, a member of the group, is dously contagious, has a high mortality rate, and known to be enzootic in rodents, especially in particular exhibits unusual nosocomial Mastomys natalensis.

REFERENCES

(1) WHO Wkly Epidem Ret 50:124-125,1975. fections of Importance (Atlanta, (2) Monath, T. P. Lassa fever and Marbug 1975). virus disease. WHO Chron 28:212-219, 1974. (4) Wulff, H. T., and A. Fabiyi. Paper pre- (3) Fabiyi, A., and 0. Tomori. Paper pre- sented at WHO/CDC Int Symp Arenaviral In- sented at WHO/CDC Int Symp Arenaviral In- fections of Public Health Importance (Atlanta, 1975).

ENTEROVIRUSES OTHER THAN POLIOVIRUS’

Reisaku Kono2

Research is underway to elucidate the role of enteroviruses in certain sfiecific conditions-cardiac disease, ne#hritis, diabetes, hemorrhagic conjunctivitis. Heart disease has been definitely linked to five types of Coxsackievirus B; also, two ty$es of Coxsackievirus A, along with two echoviruses, are strongly suspected.

There are now 71 known types of Cardiac Diseases enteroviruses, including poliovirus types 1, 2, and 3. The apparent role of enteroviruses According to the WHO yearly virus in certain specific disorders will be dis- report, 1,295 cases of viral cardiac disease cussed. were reported in the five-year period 1969- 1973. In 300 of these cases (23.3 per cent), ‘Working paper, WHO Scientific Group on Virus the most prevalent agent was Coxsackievirus Diseases (Geneva, 1-5 September 1975); also appearing B (CBV). These data, together with other in Bol Of Sand Panam, 1977. published reports, provide good justifica- ‘Director, Central Virus Diagnostic Laboratory, National Institute of Health, Tokyo, Japan. tion for believing that CBV plays a central