Claudia McElroy in Freetown
INTERNATIONAL scientists are investigating the worst recorded outbreak of the highly contagious Lassa fever virus, which has killed at least 23 people and infected more than 150 others in eastern Sierra Leone since the beginning of March.
The statistics are based on confirmed cases admitted to hospital in the eastern provincial capital Kenema, and physicians believe the number infected may be much higher.
Lassa fever, initially spread by rats and then from person to person, causes fever, haemorrhaging, vomiting, chest pains and low blood pressure. It can kill within seven days: in 1996 about 25% of those infected died.
Although Lassa fever is endemic in eastern Sierra Leone, scientists are baffled by the recent huge increase in cases. About 35 are confirmed each year. There were only 10 reported cases in March last year.
One of the visiting scientists from the Centre for Disease Control in Atlanta, Georgia, said: “Since the rat population had been left undisturbed for several years in villages abandoned because of the war, there has been an explosion in their numbers. People now returning to their homes often don’t have the resources to protect their food or kill rats, while overcrowding increases the risk of human transmission. But the truth is we don’t exactly know the reasons why.”
The disease takes its name from Lassa village in northern Nigeria, where it was first recorded in 1969. Although cases of Lassa fever appeared throughout West Africa, it was in Sierra Leone that scientists from the disease control centre first isolated the virus in rats in 1971.
“Everyone was focusing on the new killer disease,” he said. “At that time there was considerable interest by both the United States and Russian armies . although since the end of the cold war military interest in biological warfare has decreased. Since more is now known about Lassa, it would not really be useful as a biological weapon anyway.”
The only known cure for Lassa fever, Ribavirin, was until recently produced by the US company Viratech, which holds the patent rights. The cost of Ribavirin shot up to R4 445 a dose when it was falsely believed to be useful in the treatment of the HIV virus and the fatal Hunter’s virus.
The centre, which donates Ribavirin for the treatment of Lassa fever, says its stocks are depleted but for a small emergency supply. The other main supplier to the region, the British Medical Emergency Relief International, says its stocks are exhausted.
Two unlicensed sources of the drug have been identified in China – the Beijing and Shanghai Medical companies. The Chinese Red Cross has offered to donate a consignment of Ribavirin to the Sierra Leone government. The unlicensed form of the drug costs about R2,70 a dose.
Producing a Lassa vaccine is not a priority for the centre, as outbreaks of the virus have been restricted to a relatively small area. Social and political unrest in the region is considered to make investment in research commercially unviable.
The centre admits that interest in “exotic” diseases such as Lassa fever stems from fear that they could spread to America – even though there has been no transmission of secondary cases outside Africa.