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A_50_year_old_engineer_in_your_hospital_out-patient department_is_found_to_be_febrile_and_to_have_returned_two_days earlier_from_West_Africa._Discuss_the__problems_posed_by_this situation.

 

The marked increase in traveling to far-flung and exotic locations has made the appearance of exotic infectious diseases much more frequently in the UK. Exotic viral infections in West Africa ranges from a mild arboviral illness to a life-threatening Lassa fever. The following infectious diseases should be sought for and excluded from this patient;-

1. Bacterial and parasitic diseases - malaria and typhoid fever are two common infectious diseases which occur in West Africa and should be excluded from this patient. A blood film for malaria should be taken and inactivated at the bedside of the patient and the result be available before other investigations. Other possible infections that should be considered are rickettsiae infection, leptospirosis, amoebic liver abscess etc.

2. Common ubiquitous viral diseases - one must not forget that certain ubiquitous viral diseases such as influenza is just as likely to strike a person in West Africa as in the UK and thus should be excluded as a possible diagnosis

3. Arboviruses - arboviruses of the togavirus, bunyavirus and flavivirus families are common in West Africa. The diseases caused ranges from an inapparent or mild flu-like illness to a life threatening encephalitis or haemorrhagic fever. Laboratory diagnosis of arboviral infections is difficult as there are so many different viruses which could be involved. Moreover, a few of these agents are classified as group 4 pathogens which requires specialized and expensive facilities to work with. Cases of exotic arboviral infection imported into the UK would not constitute a threat to public health or a threat to health workers as human to human transmission cannot take place in the absence of the insect vector.

4. Yellow fever and dengue - these two arboviral diseases are common in West Africa and are responsible for much morbidity and mortality. The diseases are transmitted to man via mosquito bites. In the case of yellow fever, the reservoir is in monkeys. The presence of an infected person in the UK would not constitute a public health problem since the mosquitoe vector is not that active in the UK.

5. Lassa fever - lassa fever is a prevalent infection in West Africa. Lassa fever is a zoonosis and man are infected through contact with infected urine of the multimammate rat, which is the natural host. The clinical manifestations vary from a mild undifferentiated febrile illness to a fatal disseminated multi-system disease. Typically pharyngeal signs are present and the lungs are affected. Neurological symptoms and signs may be present as well as haemorrhagic phenomena. Moreover, human to human spread is known to occur and hospital personnel had been infected in the past and thus cases of imported Lassa fever would pose a serious threat to hospital and laboratory workers. Lassa fever is classified as a group 4 pathogen. The antiviral drug ribavirin had been reported to have a possible beneficial effect on the illness.
 
 

Management

A detailed history should be obtained from a patient such as whether he had many mosquitoe bites, was there contact with a person with a febrile illness, had he been vaccinated against yellow fever, and whether he worked in rural areas where there is a high risk of exposure to lassa fever due to contact with the excretions of the multimammate rat.

Until proven otherwise, it would be prudent to presume that this patient had Lassa fever and appropriate measures be taken. The patient should be admitted to hospital and put into a single room under strict isolation. A room with negative pressure is not required unless there is copious amount of blood, body fluids and excretion which may result in aerosols. In that instance, self-contained respirators may be worn when entering the room. Gloves, gowns, plastic aprons, and high efficiency filter masks should be worn on entering the room and visitors be excluded. Unnecessary equipment and furniture should be removed from the room. Trained staff should be use in the care of the patient.

The hospital staff and laboratory staff should be informed and counseled about the possible diagnosis and the hospital administrators informed. Procedures that minimize percutaneous exposures should be emphasized. All clinical waste should be disposed of in labelled leakproof bag which are then incinerated or autoclaved before incineration. Excretions from the patient should be treated by autoclaving, chemical toilet, or disinfectant before disposal. Linens should be sent to the laundry in sealed, labelled, leakproof bags. They could either be autoclaved or incinerated, although a normal hot-wash cycle will be sufficient if universal precautions are adopted. Solid wastes from the patient, such as syringes and needles should be incinerated. Spills should be covered with hypochlorite and then removed.

Paired blood specimens should be taken for serological diagnosis and the blood should be inactivated by putting in a hot waterbath at 56oC before testing is carried out, or preferably inactivated by Triton X-100 or B-propiolactone. Blood, throat swab, urine and faeces may be taken for the purpose of virus isolation but this may prove to be difficult and impractical as group 4 containment facilities would be required and the specimens may need to be sent to a specialized centre such as Porton Down. Other clinical tests should be kept to a minimum but if necessary for patient care, may be carried out in a Class II cabinet under Class III containment. Equipment used should be properly decontaminated afterwards.

Empirical treatment with IV ribavirin may be started if the clinical suspicion of lassa fever is very strong, such as the presence of pharyngitis, myalgia, GI and/or pulmonary involvement. Should a member of the hospital staff be involved in an incident such as a needle stick injury which may carry a high probability of exposure, then postexposure prophylaxis against Lassa fever may be desirable and oral ribavirin may be used as well as Lassa immunoglobulin, should the latter be available. There is no specific antiviral therapy available against yellow fever, dengue, and other arbovirus infections.

To conclude, a febrile person who has just returned from West Africa poses a diagnostic as well as a management problem. Although many different agents may be involved, it would be prudent to treat it as a potential case of Lassa fever until proven otherwise.

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