The story of Lassa

No, not the dog but that of the fever.

The story begins in 1969 in a 60-bed bush American hospital in the northeastern Nigerian town of Lassa (hence the name Lassa fever).

An elderly US missionary female nurse fell sick. The usual anti-malarial and antibiotic treatment was of no avail. She was airlifted to a bigger US missionary hospital in Jos, Nigeria, but she died soon after admission.

Within a few days another missionary nurse was stricken and succumbed too. Yet another nurse fell sick but the USA Missionary Society got alarmed and evacuated her to Columbia Presbyterian Hospital, New York. Here two laboratory workers got infected in turn and one died.

So three of the first five patients died, a frightening mortality rate of 60 per cent.

The next page of the story was written when specimens of blood, urine and pleural fluid from the first (1969) patient were inoculated in monkey kidney cells in laboratory test tubes; within a few days the cells were seen to be heavily infected by an unusual virus.

Furthermore, when minute quantities of serum from the three (1969) patients were injected into the brains of laboratory mice, the mice were found to be infected for life, yet showed no ill-effects and grew normally.

Finally, electron-microscope pictures of material from infected cell cultures revealed a hitherto unknown spherical virus, with no internal structure except for some granules looking like polka dots. The overall impression was that the new virus looked like the old-fashioned sea-mines with knobs used in naval warfare.

By now the clinical signs and symptoms of this new disease were well defined, the virus identified, but where did the Lassa virus come from? By testing many species of African animals, one species was found to be the sole natural carrier of the virus. This was the timid multimammate rat (Mastomys natalensis).

Humans contracted Lassa fever by direct or indirect contact with this rodent which contaminated living quarters with its excretions, and the food and water supplies.

On June 28, 2005 a report was published by the US Army scientists (Fort Detrick) and the scientists of the Canadian Public Agency that they had successfully genetically engineered a vaccine against this deadly disease.

As the rats are ubiquitous in tropical Africa, the only hope of controlling this disease, which kills more than the more publicised Ebola and Marburg fevers, is a vaccine.

Lassa fever has probably met its Waterloo!