904

The plateau of the Sahara measures about 3’ 5 million squaremiles. Its topography varies from rocky wasteland, known as thehammada, through an intermediate zone of stones and gravel (serir),to the loose and mainly sandy area with drifting dunes (the erg). Thehighway has been built at altitudes of between 300 and 600 m,except in the Ahaggar highland (which rises to 3000 m) where itruns at 1400 m. The climate varies with latitude and altitude: the

temperature ranges from 50°C at noon in summer to below 0°C atnight in winter, and humidity is very low. Rainfall is virtually nil,but in parts of the desert sudden storms may create raging torrentsin the usually dry wadis. In these arid areas subsurface water maycollect in low-lying places and form saline pools. Except in isolatedsmall or medium oases, the population is scarce and consists ofnomadic tribes, who have been greatly affected by recent droughts.Most of the oil and mineral industries are in the north-easternSahara, away from the highway.The growing economic importance of the trans-Saharan highway

is illustrated by the spectacular rise in vehicular traffic. Reportsfrom the three road-posts at the borders with southern states of WestAfrica showed that the number of vehicles crossing the frontiersrose from 2822 in 1978 to 8036 in 1984 and the number of travellers

entering Algeria from the south increased from 3530 in 1978 to12 434 in 1984. Of the 410 cases of malaria reported in Algeria overthe past few years, 70% were caused by Plasmodium falciparumbrought from tropical Africa. A traveller from Tanzania withchloroquine-resistant malaria served as a reminder of potentialdifficulties. Malaria imported by travellers has been reportedpreviously,3 but its increasing relevance to the countries of NorthAfrica where malaria had been eliminated is emphasised by a studyin.Libya.4 4

Epidemics of P vivax malaria have occurred in Algeria in the past.Sporadic cases of falciparum malaria have been common and one ofthe local anophelines has been the vector.2 There are three speciesof malaria vectors in Algeria and other western Mediterraneancountries: Anopheles labranchiae, A sergenti, and A multicolor.2 Alabranchiae, the most important, is found in coastal areas and thenorthern zone of the Sahara; it breeds in both fresh and brackishwater of marshes, ditches, and streams. Its ability to transmit thetropical strains of P falciparum is in some doubt. A sergenti is also animportant vector, breeding in various types of water, even in thedeep dark wells and canals (foggaras) of some oases. A multicolor issuspected to be a vector in oases of the northern Sahara; its larvaethrive even in highly saline surface water.5 5

Some workers believe that imported tropical strains of

P falciparum are unlikely to cause a resurgence of malaria because ofthe doubtful ability of the main vector, A labranchiae, to transmit thedisease. Possibly the greatest danger is that the two notorioustropical malaria vectors, A gambiae and its close relative A

arabiensis, would establish themselves in Algeria along the trans-Saharan route. The formidable climatic barriers would discouragetheir settlement in northern areas of the Sahara, but the southernoases of the Ahaggar, Tidikelt, and Tassili areas would bevulnerable to invasion by these highly adaptable and resistantmalaria vectors. Air-conditioned motor vehicles could providelong-distance transport of these mosquitoes. Moreover, theincreased water supply from deep reservoirs in some new

agricultural and industrial enterprises in southern Algeria maycontribute to more permanent colonisation by the two species. Theinvasions of Brazil and Upper Egypt in the 1940s and recent reportsof long-distance transport by aircraft of infected tropical vectors ofmalaria to northern Europe serve as warnings. Greater vigilanceand effective preventive measures are needed.

Although the implications of the trans-Saharan highway werediscussed briefly at a WHO meeting in 1979,6 more decisive actionis needed, since, in order to increase rice production, various water-impoundment projects are proposed in many North Africancountries.

Only 50 years ago Bovill7 wrote: "The Sahara presented aninsuperable barrier to regular intercourse [of North Africa] with theSudan, and at no period did man contemplate the crossing of the

Sahara, except as an enterprise involving grave risk and demandingthe greatest hardihood." Today, the hardihood has virtually gone,but the risks are there, although of a different kind.

I thank Dr E. H. Benzerroug and Dr R. Gassabi, of the National Institute ofPublic Health, Algiers, for their help and Mr Chris Allen for the map.

Wellcome Tropical Institute,200 Euston Road,London NW1 2BQ L. J. BRUCE-CHWATT

REFERENCES

1. World Malaria Situation 1982. World Health Statist Quart 1984; 37: 130-61.2. Ramsdale CD, de Zulueta J. Anophelism in the Algerian Sahara and some implications

of the construction of a trans-Saharan highway. J Trop Med Hyg 1983; 83: 51-59.3. Bruce-Chwatt LJ. Imported malaria-an uninvited guest. Br Med Bull 1982; 38:

179-84.4. Gebreel AO, Gilles HM, Prescott JE. Studies on the sero-epidemiology of endemic

disease in Libya. Ann Trap Med Parasit 1985; 79: 341-47.5. Stafford Smith DM. Mosquito records from the Republic of Niger, with reference to

the construction of the new trans-Sahara highway. J Trop Med Hygiene 1981; 84:95-99

6. Proceedings of the coordination meeting on the prevention of the reintroduction ofmalaria in the countries of the western Mediterranean. (Erice, Italy; 1979).Copenhagen: WHO Regional Office, ICP3MPD 008/S, 1980.

7. Bovill EW. Caravans of the old Sahara. Oxford: Oxford University Press, 1933.

United States

CYANIDE IN TYLENOL CAPSULES

EXCEPT for ’Tylenol’ (paracetamol), over-the-counter medicineswill continue to be available in capsules in US drugstores. 8 personshave died since 1982 after taking tylenol capsules containingcyanide inserted by some evil-doer. The makers ofnon-prescriptiondrugs generally will not follow the lead of Johnson & Johnson, whomarket tylenol and who have stopped producing it in capsule form.Henceforth the drug will be sold only as tablets and caplets (tabletsshaped like capsules).

John T. Walden, spokesman for the Proprietary Association, thetrade association for non-prescription drug manufacturers,explained that capsules are easier to swallow than tablets and permitthe use of timed-release formulations. He pointed out that tamper-proof packaging is an impossibility. "You can’t make tamperproofbank vaults. Bank robbers prove that."

The answer is not that easy for Johnson & Johnson. For the secondtime its executives have had to endure a national scare over a verypopular product. 7 people in Chicago died in 1982 after takingtylenol capsules adulterated with cyanide. In February of this year a23-year-old woman in Peeksgill, north of New York City, took apoisoned tylenol capsule and died. Soon after that, the death of aman of 32 in Nashville, Tennessee, was regarded as possibly but notcertainly connected to tylenol.

No-one has been apprehended for these seemingly random andpurposeless murders. The authorities believe there was more thanone perpetrator. The Chicago tamperings were crude and obvious.In the New York poisoning, the bottle which the victim bought wasso craftily opened and resealed that it took days for the FederalBureau of Investigation to discover evidence of tampering. Thekiller had to break three seals: adhesive on the outer carton, a plasticband heat-shrunk to the cap, and a foil seal laminated to the lip of thebottle inside the cap.

In retrospect, Johnson & Johnson’s chairman, James E. Burke,believes he made the wrong decision in not taking tylenol capsulesoff the market in 1982. His management of the crisis, nevertheless,drew praise from President Reagan. He told a group ofbusinessmenthat Mr Burke "has lived up to the highest ideals of corporateresponsibility and grace under pressure".