Using biostatistics to detect disease outbreaks

Jul 15, 2008
Using biostatistics to detect disease outbreaks
Illustration of an influenza virus attaching to a cell membrane: Professor Louise Ryan is working with CSIRO to distinguish cases of the flu from other disease events. Image by CSIRO

An internationally recognised authority in biostatistics, Harvard University Professor Louise Ryan, is working with CSIRO researchers to help improve the way statistics are used to detect disease outbreaks in Australia.

A recipient of the Australia-Harvard Fellowship, Professor Ryan – the Chair of the Department of Biostatistics at the Harvard School of Public Health – arrived in Australia in June to work on a project developing statistical methods that could distinguish cases of the annual flu from reactions to a pollution event or food poisoning.

“We are at the point now where technology is enabling us to access huge amounts of data related to health, for example real-time information on hospital admissions, including symptoms and locations,” Professor Ryan says. “Developing the statistical and computational tools to sort through these data and detect patterns is a real challenge.”

The leader the Health Data and Information research group within CSIRO's Preventative Health National Research Flagship, Dr Christine O'Keefe, says Professor Ryan's visit will help CSIRO to improve the standard of information being generated from health data in Australia.

"Professor Ryan's visit will help CSIRO achieve its aim of generating better information from health data, contributing to improved health outcomes for Australians," Dr O'Keefe says.

Professor Ryan will be contributing to the development of a model of what the ‘usual’ behaviour of a disease occurrence would be.

“Using statistics, we are able to predict what the usual behaviour of something like winter flu would be, and then to understand the variations on normal behaviour that are likely,” Professor Ryan says.

“Its important to understand that within the definition of what is normal for something like the flu, there is still huge variation between the time of the year that it can occur, the severity of the symptoms and even the mortality rate.”

This means that statisticians will be able to provide the best possible advice to decision-makers so they can make decisions about how to allocate resources.

“Effective surveillance methods require finding the right balance between declaring an unusual event where there is none, versus missing an outbreak that is occurring. We need to develop methods of detection that will have high sensitivity to important signals but that also do not give us too many false positives, which can lead to a waste of resources,” Professor Ryan says.

Surveillance methods have the potential for many areas of application in addition to health, for example, traffic accident monitoring and water quality monitoring.

The Australia-Harvard Fellowship is awarded by the Harvard Club of Australia Foundation to support learned exchange between Harvard University and Australia through collaboration with senior Australian research organisations.

Professor Ryan will address an international workshop on spatio-temporal modelling in Sydney on 29 July.

Provided by CSIRO

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wilfriedsoddemann
not rated yet Jul 16, 2008
CUT THE CHAIN OF INFECTIONS !

Spread of avian flu by drinking water:

Proved awareness to ecology and transmission is necessary to understand the spread of avian flu. For this it is insufficient exclusive to test samples from wild birds, poultry and humans for avian flu viruses. Samples from the known abiotic vehicles as water also have to be analysed. Proving viruses in water is difficult because of dilution. If you find no viruses you can not be sure that there are not any. On the other hand in water viruses remain viable for a long time. Water has to be tested for influenza viruses by cell culture and in particular by the more sensitive molecular biology method PCR.

Transmission of avian flu by direct contact to infected poultry is an unproved assumption from the WHO. There is no evidence that influenza primarily is transmitted by saliva droplets: %u201CTransmission of influenza A in human beings%u201D http://www.thelan...op=true.

There are clear links between the cold, rainy seasons as well as floods and the spread of influenza. There are clear links between avian flu and water, e.g. in Egypt to the Nile delta or in Indonesia to residential districts of less prosperous humans with backyard flocks of birds and without a central water supply as in Vietnam: http://www.cdc.go...829.htm. See also the WHO web side: http://www.who.in...und.pdf. That is just why abiotic vehicles as water have to be analysed. The direct biotic transmission from birds, poultry or humans to humans can not depend on the cold, rainy seasons or floods. Water is a very efficient abiotic vehicle for the spread of viruses - in particular of fecal as well as by mouth, nose and eyes excreted viruses. Infected humans, mammals, birds and poultry can contaminate drinking water everywhere. All humans have very intensive contact to drinking water. Spread of avian flu by drinking water can explain small clusters in households too.

Avian flu infections may increase in consequence to increase of virus circulation. Human to human and contact transmission of influenza occur - but are overvalued immense. In the course of influenza epidemics in Germany, recognized clusters are rare, accounting for just 9 percent of cases e.g. in the 2005 season. In temperate climates the lethal H5N1 virus will be transferred to humans via cold drinking water, as with the birds in February and March 2006, strong seasonal at the time when (drinking) water has its temperature minimum.

The performance to eliminate viruses from the drinking water processing plants regularly does not meet the requirements of the WHO and the USA/USEPA. Conventional disinfection procedures are poor, because microorganisms in the water are not in suspension, but embedded in particles. Even ground water used for drinking water is not free from viruses.

In temperate regions influenza epidemics recur with marked seasonality around the end of winter, in the northern as well as in the southern hemisphere. Although seasonality is one of the most familiar features of influenza, it is also one of the least understood. Indoor crowding during cold weather, seasonal fluctuations in host immune responses, and environmental factors, including relative humidity, temperature, and UV radiation have all been suggested to account for this phenomenon, but none of these hypotheses has been tested directly. Influenza causes significant morbidity in tropical regions; however, in contrast to the situation in temperate zones, influenza in the tropics is not strongly associated with a certain season.

In the tropics, flood-related influenza is typical after extreme weather. The virulence of influenza viruses depends on temperature and time. Especially in cases of local water supplies with %u201Cyoung%u201D and fresh influenza-contaminated water from low local wells, cisterns, tanks, rain barrels, ponds, rivers or rice paddies, this pathway can explain H5N1 infections. At 24°C, for example, in the tropics the virulence of influenza viruses in water exists for 2 days. In temperate climates with %u201Colder%u201D water from central water supplies, the temperature of the water is decisive for the virulence of viruses. At 7°C the virulence of influenza viruses in water extends to 14 days.

Ducks and rice (paddies = flooded by water) are major factors in outbreaks of avian flu, claims a UN agency: Ducks and rice fields may be a critical factor in spreading H5N1. Ducks, rice (fields, paddies = flooded by water; farmers at work drink the water from rice paddies) and people %u2013 not chickens %u2013 have emerged as the most significant factors in the spread of avian influenza in Thailand and Vietnam, according to a study carried out by a group of experts from the United Nations Food and Agriculture Organization (FAO) and associated research centres. See http://www.un.org...ID=26096&Cr=&Cr1

The study %u201CMapping H5N1 highly pathogenic avian influenza risk in Southeast Asia: ducks, rice and people%u201D also concludes that these factors are probably behind persistent outbreaks in other countries such as Cambodia and Laos. This study examined a series of waves of H5N1, a highly pathogenic avian influenza, in Thailand and Vietnam between early 2004 and late 2005. Through the use of satellite mapping, researchers looked at several different factors, including the numbers of ducks, geese and chickens, human population size, rice cultivation and geography, and found a strong link between duck grazing patterns and rice cropping intensity.

In Thailand, for example, the proportion of young ducks in flocks was found to peak in September-October; these rapidly growing young ducks can therefore benefit from the peak of the rice harvest in November-December, at the beginning of the cold: Thailand, Vietnam, Cambodia, Laos %u2013 as opposed to Indonesia %u2013 are located in the northern hemisphere.

These peaks in the congregation of ducks indicate periods in which there is an increase in the chances for virus release and exposure, and rice paddies often become a temporary habitat for wild bird species. In addition, with virus persistence becoming increasingly confined to areas with intensive rice-duck agriculture in eastern and south-eastern Asia, the evolution of the H5N1 virus may become easier to predict.

Dipl.-Ing. Wilfried Soddemann - Epidemiologist - Free Science Journalist soddemann-aachen@t-online.de http://www.dugi-e...ion.html