On 22 September 2003, Dr Mike Ryan gave the 11th annual John Snow Society Pumphandle Lecture at the London School of Hygiene and Tropical Medicine.
In the last half of the 20th century, following the development of modern antibiotics and vaccines, there were confident predictions that infectious disease would soon be vanquished - and no longer be a priority issue for public health. While there have been success stories, we know now that such optimism was sadly misplaced, particularly when considering the continuing global impact of infections. To date only one infection, smallpox, has been eliminated in its natural environment: the WHO announced official eradication of smallpox virus in 1980. In the decades following this magnificent achievement, several epidemics of new harmful micro-organisms (pathogens) have emerged, such as, legionnaires' disease, cryptosporidiosis (the parasite associated with animal and water spread), AIDS/HIV, resistant bacteria in hospitals and campylobacter, now the commonest cause of bacterial intestinal infection. Newly emerging pathogens have been accompanied by re-emerging pathogens such as cholera and tuberculosis. The zeitgeist of globalisation, a term which could be said to characterise the modern age, includes the much increased potential for rapid spread of pathogens through food imports, travel and in the very air we breathe. So the epidemic in 2003 of another new disease, SARS (Sudden Acute Respiratory Syndrome) was a particularly appropriate topic for the 11th Pumphandle lecture, delivered by Dr Mike Ryan for the John Snow Society on 22nd September at the London School of Hygiene and Tropical Medicine. Dr Ryan is the coordinator of the Global Alert and Respiratory Unit of the World Health Organization (WHO), a unit formed in 1996 to counter infections of global importance, such as Ebola - and now, SARS.
The SARS story started quietly in a remote part of China (Table 1). In February 2003, local health workers made unofficial reports of cases of atypical pneumonia with a high death rate. A few days later this was officially confirmed and similar cases were identified in Hong Kong and Viet Nam. The illness started with fever and dry cough, not unlike influenza, but rapidly progressed in some cases to difficulty in breathing: up to 10% needed mechanical ventilation and up to 20% required treatment in intensive care units. Many people also developed diarrhoea, a point which helped in the epidemiological detective work later. Within a month, evidence of 'globalised' infection came from Ontario and Singapore and increasing concern about the role of international travel in spreading the infection. By this stage, the WHO Global Alert & Respiratory Unit had already coordinated teams to affected areas and was under intense pressure from the media. Mostly existing with only a few hours sleep, the team at the WHO painstakingly unravelled the epidemiology of this new infection, traced to a previously unknown type of corona virus. Thanks to email, teleconferencing and other forms of communication, rapid progress was made by linking with units around the world: this is the first epidemic where new communications technology played a major role. The team also worked to basic public health principles, trying to find answers to those key questions familiar to outbreak investigators: what is the infection; what does it do to people; how does it do it - and how do we stop it? With no vaccine and no specific treatment, the answer to that last question rests on public health measures: quarantine of known cases and avoiding contact with those infected. The team composed advice based on simple but effective rules - how do we detect it, how to we protect people from it. The epidemic has raised questions about facilities for artificial ventilation and for the prevention of infection by air filters and quarantine.
During the early stages of the outbreak, there was inevitably criticism of lack of progress and decisions: many preliminary decisions about intervention measures had to be made with limited information. The advice about international travel was controversial, for example the removal of Ontario from tourist itineraries at one stage. Thus Canada and other countries experienced yet another blow to tourism, still not recovered after the 11 September atrocities of 2001. Yet a glance at the chronology shows that continual progress was made throughout the epidemic. Research investigations in Hong Kong were particularly helpful, showing the potential for airborne spread in the high number of affected health workers and in the cases in a hotel and an apartment block. In the latter, a block in the Kowloon Bay area of Hong Kong, 41% of cases were associated with just one wing and two thirds had had diarrhoea. Environmental investigation revealed a combination of a cracked sewage pipe and contamination of the 'U-bend' trap in toilets. This was believed to have infected people in apartments on different levels of the wing via aerosol and droplet spread. While not a typical way in which SARS spread, it provided a neat 'water-associated' link for the Pumphandle Lecture: Dr John Snow would surely have approved of this detective work!
Now that the SARS information is much more complete, several important preventive measures have emerged. First, the virus is highly infective and rapid isolation with barrier nursing is essential. Second, there is clear evidence that it was spread by travel, so restrictions on journeys, particularly by air, will be essential if SARS re-emerges. Smallpox is now known to have spread throughout the world, centuries ago, via the silk trading route. Thirdly, there is potential to develop a vaccine. However, vaccines are not without problems and during the eradication of smallpox the vaccine side effects included death or disability. Perhaps one of the strongest messages is that we lose our traditional public health skills and tools at our peril - when a new infection emerges, the tried and tested ways of controlling epidemics are our best defence. In the final part of Dr Ryan's fascinating lecture, he placed the SARS epidemic into the perspective of the way public health - and its threats - have developed over the last two centuries. Prevention methods based on the miasma theory (disease spread by 'evil vapours' in overcrowded or poor conditions) led to improvements in sanitation and ventilation that reduced the spread of microbes, although the 'miasma' emphasis, combined with the limited understanding of microbial spread in the early days of the germ theory, led to a possibly over-militarised approach. Now that the complexities of environmental spread are more clearly understood, we should be in a strong position for the current set of potential threats (Table 2). Global public health campaigns have reduced levels of some of the old enemies: guinea worm, poliomyelitis, measles, leprosy and neonatal tetanus. But the resurgence of many others, such as malaria and TB, is partly due to the patchy and, in some countries, declining state of public health services. Basic core standards of surveillance need to be matched by global partnership in the fight to counter those bugs that respect no borders. SARS has taught us "what should be in there", such as enhanced surveillance, coordination of a "network of networks", rapid response and attention to emerging issues such as animal-human transmission of infection. The SARS experience also showed that the coordination and intervention required does not come cheap: the overall cost of the public health work on the epidemic was an estimated $22 million dollars, way over the modest budget of the WHO unit. Considerable powers of persuasion and diplomacy were needed to raise the funds required: but another lesson of SARS was that the price of uncoordinated or tardy action would have been an even greater economic cost to airlines and hotels. It is a measure of the success of the measures taken that there was rapid recovery of the impact on tourism. Delayed recognition and reporting of this type of epidemic remains a difficult issue: the first major revision of the International Health Regulations since 1969 has been making slow progress over the last five years. Meanwhile, Dr Ryan and his colleagues in the Global Alert and Response Unit continue to build on three basic pillars of public health: containment of known risks, responding effectively to the unexpected and improving awareness.
This well attended Pumphandle lecture finished in the traditional way with the ceremonial removal of the pump handle on the Society's pump - and a lively discussion and Annual General Meeting afterwards at the John Snow pub.
Hon Secretary, John Snow Society
|11 February||Unofficial reports of deaths from an unusual pneumonia in Guangdong Province, China|
|14 February||Official confirmation of epidemic by Chinese Government: 305 cases, 5 deaths|
|19 February||Two cases of Avian Flu (H5N1) in Hong Kong, linked to contacts in mainland China|
|26 February||Cases in Hanoi, Viet Nam|
|4 March||77 cases in medical staff at a hospital in Hong Kong|
|5 March||7 cases in medical staff at a hospital in Hanoi|
|8 March||WHO teams arrived in Hanoi & Hong Kong|
|12 March||First Global Alert|
|14 March||4 cases in Ontario, Canada & 3 in Singapore|
|15 March||Urgent Global Alert & broadcast of the case definition: advice re: travel risk given to international travellers|
|17 March||Establishment of 'virtual' research networks using communications technology|
|26 March||Concern about continuing travel of people suspected to be infected with SARS, although the risk to adjoining passengers assessed as 'non-quantifiable'|
|27 March||3rd Global Alert|
|31 March||Outbreak of SARS at hotel in Hong Kong: confirmation of potential airborne threat|
|2 April||Passengers advised to postpone non-essential travel to Hong Kong or Guangdong Province.|
|April-August||Epidemiological and laboratory investigations confirmed the mode of spread, incubation, course of the illness and the nature of the virus, a new corona virus|
|21 September||Latest toll of cases: 8097, of whom 774 had died. 30 countries involved, although 92% of known cases were infected in China.|
|Type of infection threat||Examples||Key points for public health|
|Emergence of new pathogens||AIDS/HIV, Legionella, SARS||
|Resurgence of 'old' pathogens||Tuberculosis, Malaria, Cholera, Dengue fever, Ebola, Rift Valley Fever, West Nile Fever, Anti-microbial resistance||
|Accidental release||Bovine Spongiform Encephalitis/ CJD||
|Deliberate/ malicious release||Anthrax, smallpox||