The idea of rampant malaria in Moscow might seem implausible - the city is as far north as Glasgow - but the disease was prevalent in the capital until the Fifties. Travellers need not be unduly alarmed, however. 'The chances of a visitor contracting malaria are small,' Dr Peter Barrett, of the Medical Advisory Service for Travellers Abroad (Masta), says. 'The most likely hazard is just nuisance bites, so pack some repellent.'
Visitors to the former Soviet republics of Azerbaijan and Tajikistan should take malaria pills, however.
The danger from diphtheria is a subject of some disagreement. An outbreak of this serious disease, which affects the respiratory system, has afflicted more than 8,000 people in the former USSR. In Britain, universal vaccinations against diphtheria were introduced in 1942, so anyone born since then should have some immunity. Ideally, intending visitors should have a booster. The problem is that low-dose supplies of the vaccine seem to have dried up in the UK.
Masta says the risk of infection to short-term visitors is so low that travellers should not be deterred from going, but some intending holidaymakers are facing problems from insurers and tour operators. One couple about to embark on a White Sea cruise were told their insurance cover would be invalidated unless they had diphtheria jabs. Others found their tour operator refusing to take them without evidence that they had received a booster. Under European Community regulations, tour operators bear heavy responsibilities for the health of their clients, but they would appear to be taking the diphtheria scare too seriously.
One danger that should not be underestimated is the tap water in St Petersburg. Visitors to Russia's second city should be aware that water supplies are contaminated by the parasite giardia, which causes long- term stomach problems; on a visit a fortnight ago, I was disinclined to trust the murky brown liquid that oozed out of the taps in my hotel bathroom even for brushing my teeth. (I can also vouch for the malevolence of Russia's burgeoning mosquito population.)
Two other mosquito-borne health hazards have come to light this week. A plague of the insects has descended on Poland's Baltic coast, according to the Polish news agency PAP. Swarms of mosquitoes are tormenting Szczecin province, keeping people off the beaches and making driving dangerous. Travellers to the Aswan area of Egypt are also being put at risk by mosquitoes, which have caused an outbreak of the potentially fatal Rift Valley fever. There is no form of immunisation against it, so visitors must avoid being bitten. 'Use repellent, cover up at dusk and sleep under a mosquito net,' Dr Barrett advises.
Health advice for up to six countries can be obtained by calling the Masta information line: 0891 224100. You supply details of your planned journey, and receive a health brief by post. The price of the service is simply the cost of the call to this premium-rate number; the average is pounds 2.