You are here: MEDICA Portal. Our Topics in 2009. Topic of the Month February: Forgotten Diseases. Infectious Disease.
„In Long Years of Detail Work“
A death cow in the nowhere
can cause an epidemic; © SXC
MEDICA.de spoke to Jürgen May, head of the working group infectious disease epidemiology at the Bernhard-Nocht-Institut, about an eradicated illness, a disease that could be eradicated soon and how Europe can be protected against epidemics.
MEDICA.de: Mister May, in 1980, the World Health Organization (WHO) declared that smallpox are eradicated. Is there really no danger that the illness could come back some day?
Jürgen May: There is a theoretical danger that this virus could emerge once again. Some people believe that smallpox viruses are kept in laboratories in Russia and the USA. It is not proven though and I cannot tell whether the pathogen could be used as a biological weapon. Actually, no case of human pox has appeared during the last 40 years.
MEDICA.de: When is a disease considered eradicated and who decides on this?
May: The WHO decides. Over a certain period, no single case of illness may be reported. The duration of that period varies from disease to disease.
MEDICA.de: So far, only smallpox are regarded as defeated.
May: Yes. However, there are some diseases that could be erased soon. Polio is on the list, for example. Basically, only single cases occur. Yet trouble spots delay the eradication: there are some 100 cases per year in an area in Nigeria, and from there the illness spreads to other countries again and again. The local authorities in Nigeria do not permit immunisations. But to eradicate the disease a certain percentage of the population has to be vaccinated. This is called herd immunity. By vaccinating many humans, the others are protected as well because the pathogen cannot spread easily any more.
MEDICA.de: Why is it so difficult to eradicate illnesses?
May: In poor countries it is simply a problem to reach the people. Even if free immunisations are offered, the people still need to understand that they are important. There are logistic and infrastructural problems, for example the vaccine has to be transported refrigerated, without electricity. Even though a very effective vaccine against measles is available, there are still around 500,000 fatalities each year. This shows: it is mainly a problem of distribution. Regarding bacterial diseases such as tuberculosis, resistances play a major role. Patients with tuberculosis have to take their medications regularly over a long time, around half a year. If they do not take them for only a week, the bacteria might already have become resistant, so that the antibiotics have no effect. Then, the treatment becomes considerably more difficult.
MEDICA.de: What role do bats, rats and other animals play?
May: Many of the illnesses spreading uncontrolled are animal diseases initially. Such diseases are even harder to extinguish. To stop the circulation, the infection of humans and animals has to get under control. Contagioned animals perish somewhere in the wilderness and carry the pathogen forward, for example via insects. This applies for the sleeping sickness, the West Nile virus, SARS or the avian flu: chickens galore were killed. But if all infected chickens were killed is unknown.
MEDICA.de: Does that mean SARS could come back any time?
May: It cannot be excluded. It is unratable in which animal populations SARS still circulates.
MEDICA.de: In the 60s, the sleeping sickness, an African disease that can end fatally, was considered as good as defeated. Only single cases were known. That is why the programmes to contain the sleeping sickness were extremely reduced – today, the illness is back again. Are control strategies nowadays more sustainable?
May: No, they are not. Wars and political instability are to blame for intermittent control measures. Diseases break out quickly in uncontrolled war zones. The people take refuge in the neighbouring countries and spread the pathogens further. That is why diseases spread as soon as means of control cannot be continued for political reasons.
MEDICA.de: As one can observe right now in Zimbabwe where the cholera spreads…
May: Yes, exactly. The cholera in Zimbabwe is a very good example: the WHO would like to act quickly, and South Africa as neighbouring country certainly as well. Still, it is not possible because a dictator decides. And then everything starts anew, in long years of detail work.
MEDICA.de: Diseases do not know borders. How to avert the epidemical spreading of introduced illnesses in Europe?
May: The surveillance of infectious diseases helps here, that is the recording of cases of illness. In Germany, the Infection Protection Act regulates which diseases are subject to registration. The list contains around 60 to 70 diseases which a physician but also other persons in responsible positions such as teachers or heads of day-care centres have to report to the public health department if they recognise them. The public health department searches for all people who had contact with the infected person and takes care for diagnosis and treatment. The Government is informed. Other necessary measurements up to the close-down of day-care centres or schools are initiated. For some years now, the European Centre for Disease Prevention and Control, the ECDC, complements the surveillance in Europe. It is still under development but participates already in the training and education of epidemiologists. In the future, it is intended to collect the European data to prevent cross-border epidemics.
The interview was conducted by Anke Barth.