Increased global travel and trade between regions has led to a growing number of cases of tropical and resurgent infectious diseases being catalogued in Europe and the USA
There has also been a notable resurgence of diseases that were considered to be on the decline in these regions, writes Faiz Kermani of Chiltern International.
The scale of modern travel is huge with there being an estimated international cross-border movement of two million people per day.
Changes in climate and the adaptation of microorganisms, enabling them to survive in previously hostile environments, have also led to these diseases gaining prominence in areas where they are not considered endemic.
The danger of these emerging incidents is that as these diseases are not expected to occur in industrialised regions, the symptoms may be confused with other illnesses.
Emerging incidents.
So-called airport malaria, representing the inadvertent transport of live mosquitoes aboard aircraft arriving from tropical regions, is one example and has become a worrying problem in recent years.
Physicians generally have little reason to suspect malaria, as the sufferers may never have travelled to a region where the disease is endemic and the symptoms can sometimes be confused with flu.
Since 1969, 13 countries reported a total of 89 cases of malaria in people living near an airport. In the USA, four cases of confirmed or suspected airport malaria were reported between 1987 and 1998.
In European cases of airport malaria the delays in correctly diagnosing the disease have led to the patients developing complications.
In one Swiss case of airport malaria, 31 days elapsed before a correct diagnosis was made.
Since 1999, West Nile fever has been a growing health problem in the USA.
The disease was previously unknown in the western hemisphere.
Mosquitoes become carriers of the West Nile virus when they feed on the blood of infected birds and can then pass on the infection to humans.
In October 2002, the Centers for Disease Control and Prevention (CDC) recorded 2530 cases of the disease with 125 deaths occurring in the USA during the year.
The ability of the virus to survive within mosquitoes over the winter months has been a key factor in the reappearance of the disease each year, but no one has been able to explain exactly how the disease arrived into the USA in the first place.
The re-emergence of tuberculosis in the western world has caused great concern as it was considered to be a disease of the past.
For example, in the UK, a 2003 report by the London Assembly's Health Committee stated that cases of tuberculosis had increased four-fold over a ten year period.
Although the committee did not believe that a crisis point had been reached it did warn against complacency and noted how drug-resistant forms of the disease were emerging.
As tuberculosis is a contagious disease any resurgence could be devastating.
According to the WHO, if the disease is left untreated, each person with active disease will infect on average between 10 and 15 people every year.
The disease continues to have a heavy impact in the developing world and trends in international travel have contributed to its reappearance in the west.
The WHO has called for coordinated international action to halt the spread of the disease. Contingency planning.
The CDC in the USA has a number of initiatives in place to deal with healthcare emergencies including those involving emerging infectious diseases.
Its emergency preparedness and response section provides information on a range of diseases to educate both the public and healthcare professionals.
The CDC has used this approach to tackle West Nile fever and provides up to date information on West Nile virus activity in the country and measures that can be taken to reduce risk of infection.
The US experience in combating West Nile virus has prompted other countries to prepare contingency plans. Although no cases of West Nile fever have been reported in the UK to date, the government published its contingency plans in May 2004.
As the infection pattern in humans involves mosquitoes and birds (and possibly other animals) the report recommended surveillance of all the species involved.
In 2003, the UK Department of Health published an infectious disease strategy called 'Getting Ahead of the Curve'.
The report outlined the threat posed to the UK by new and under-recognised infectious diseases and proposed measures for dealing with the problem.
Since the early 1970s the British government estimates that at least 30 previously unknown infectious diseases have become prominent and that fully effective treatments for them are lacking.
The government report also covered measures needed to counter bioterrorism.
The government has called for better surveillance measures, increased information exchange and stronger public education campaigns, but it also proposed the setting up of a new National Infection Control and Health Protection Agency, which would combine some of the functions of other existing public health bodies, and a local health protection service.
In February 2001, Canadian health officials were forced to take emergency measures when a woman travelling from Africa was hospitalised with suspected Ebola haemorrhagic fever.
According to the World Health Organisation (WHO) Ebola haemorrhagic fever (EHF) is one of the most virulent viral diseases known to humankind, causing death in 50-90% of all clinically ill cases.
The contingency plans involved isolation of the patient, the introduction of precautionary measures such as contamination suits, and a communication campaign to update the public and healthcare workers.
Although the fears of Ebola eventually proved groundless, the rapidity of the introduction of the Canadian emergency measures was widely praised.
Canada has had contingency plans in place for viral haemorrhagic fevers since 1978 and has periodically updated them to reflect the changes in worldwide trends for infectious diseases.
Those involved in dealing with the Canadian Ebola scare believed that their approach could form the basis of measures for dealing with infectious disease emergencies around the world.
R and D activity.
The pharmaceutical industry has come in for heavy media criticism for not being more actively involved in tackling emerging and resurgent diseases.
In a recent study by Medecins Sans Frontiers (MSF), an international medical aid agency, it was reported that despite tropical diseases accounting for 10% of the global health burden few new medicines were being developed in this area.
The pharmaceutical industry believes that the criticism is unjustified and that governments, industry and non-governmental organisations all need to cooperate further on such issues.
Public-private partnerships (PPP) are one way forward and a number of these have been set up to develop drugs for tropical diseases.
There are also a growing number of tropical disease research initiatives involving major pharmaceutical companies.
In a 2004 industry-wide survey, the Pharmaceutical Research and Manufacturers of America (Phrma) stated that 185 new drugs were being developed in the field of infectious disease.
Apart from mainstream areas in this field, the Phrma survey highlighted research being carried out to develop treatments for anthrax, West Nile virus, malaria, yellow fever, dengue fever, Japanese encephalitis, smallpox, cholera, leishmaniasis, tuberculosis and severe acute respiratory syndrome (Sars).
Although many of these were at the Phase I stage of clinical development some drugs had reached Phase II clinical trials.
A number of the major pharmaceutical companies have expanded their research into tropical diseases.
Recently, AstraZeneca opened a dedicated research facility in Bangalore, India focusing on tuberculosis.
The company committed itself to spending around US$5 million a year from 2001 to 2005 to research programmes, and will also invest another $10 million on state-of-the-art equipment.
Research staff at the Bangalore facility will also collaborate with AstraZeneca's Boston-based genomics R and D centre on infectious diseases.
In 2003, Novartis opened its Institute For Tropical Diseases at the Biopolis, Singapore purpose-built research centre.
Novartis is collaborating in a $220 million tropical disease research initiative with Singapore's Economic Development Board (EDB).
Given recent world events, bioterrorism is also a major concern.
In the USA, the FDA has published guidelines to help expedite development of drugs in this area.
The support of regulatory bodies and governments has encouraged company R and D efforts to develop drugs for a range of diseases such as smallpox, anthrax and Ebola haemorrhagic fever.
In particular, the biotech sector has a number of R and D programmes in this field.
In 2003, the US government announced a $6 billion spending to facilitate research into vaccines and treatments against potential bioterror agents.
Several European countries are also funding similar research efforts.
Outlook.
International healthcare agencies and a number of western governments and are trying to spread the message that diseases that typically affect developing countries can equally strike in affluent nations and must not be ignored.
Under investment in healthcare services and complacency are seen as major factors likely to trigger resurgence of these types of infectious diseases.
Encouraging industry R and D in these areas will also be important in combating the renewed threat posed by these diseases.
