Leading virologist advocates altruistic vaccination to prevent avian flu
Brussels, 07 Apr 2006
Professor Marc Van Ranst, a leading virology expert and advisor has outlined the latest research in two recent news-grabbing diseases - chikungunya and avian flu, but on World Health Day, also underlined the importance of more funding for diseases like tuberculosis, HIV and malaria, which are more pressing concerns and do not attract the media interest of avian flu. He outlined a common method for dealing with both avian flu and chikungunya - education. In the talk, organised by COST - European Cooperation in Science and Technical Research - he said that, should an avian flu epidemic occur, the disease could be controlled effectively by vaccinating children - the key vectors ininfluenza spread.
Professor Van Ranst is based at the Catholic University at Leuven, although he lectures throughout Europe. He presented two case studies - the first on the effects of the recent chikungunya epidemic in Réunion, and the second on avian flu. He outlined the latest research into the spread of the virus and how best to deal with it.
The chikungunya virus is spread through mosquitoes, particularly the female. 'Chikungunya is not a new virus - it was one of the first to be identified, in Tanzania in 1952 - but a latent problem. Everyone in the area typically has had access to the disease at some point in their lives.' The disease is almost identical to dengue fever in its symptoms, although it originates from a distinct virus.
The virus is most known for a fever, causing sore joints, from where it derives its name, the Swahili for 'walking bent over'. Chikungunya can cause bleeding in the teeth or gums in a quarter of cases and one in 2000 sufferers could develop meningoencephalitis, which can in certain cases cause death, although this is rare.
Professor Van Ranst was quick to point out that the disease has simply been following a normal pattern of epidemiology, with isolated outbreaks spreading to other islands over time. 'The islands will be disease free for significant periods. This strain was produced by a 'ping-pong' effect, where particular islands can infect others, so the disease goes back and forth, mutating and changing,' he said.
In this mutation, the strain was particularly virulent, leading to 75 recorded fatalities from more than 200,000 cases. As with many mosquito-borne diseases, stagnant water perpetuates the life-cycle as this is where the mosquitoes breed. The effects have attracted political interest. 'The government is fumigating large parts of Réunion, where there are a number of plants unique to that island. The effects of this fumigation programme will most likely have little effect on the disease,' he said. The measures are taking place as the number of cases is dropping, following a normal epidemiology pattern.
Turning to avian flu, the professor explained that the virus is 'enveloped', meaning it has a protein covering. Paradoxically, this 'envelopment' means that the virus is more vulnerable outside a living host. Two proteins found on the surface give the characteristic N (Neuraminidase) and H (Haemagglutinin) numbers. Haemagglutinin allows the influenza virus to enter cells, while Neuraminidase allows the new virus particles to leave infected cells, and is the target process for the drug Tamiflu, although this drug works as a post-infection prophylactic, only effective up to 48 hours after infection. Once symptoms are displayed, Tamiflu is no longer effective. 'The virus is able to mutateeasily - its RNA is segmented into eight pieces, which means it can recombine very easily, allowing strains to combine and mutate,' said Professor Van Ranst.
'The current strain, H5N1, has been identified since the 1950s, and was the fifth distinct strain discovered, in South Africa. It has popped-up every decade or so since then.' Of 16 distinct types of virus, only six are infectious to humans. Other species have not been investigated for flu infection. Birds carry all types, indicating that the virus originated in birds. 'We will never be able to eradicate influenza because we will always have birds,' he said.
'Typically, the influenza virus comes in alternating seasons, but there have been low seasons both this year and last, so I predict there will be a large infection next winter. How is flu spread? Children. They transmit it everywhere. The elderly rarely catch influenza, particularly as they have dry mucus membranes. There is a clear gap of a month between when children first catch influenza and the cases develop in the elderly population,' he said.
Vaccines are effective, but they are based on old technology - eggs. 'One egg can produce approximately one vaccine. That is a lot of eggs, and more vaccines cannot easily be made,' he said, emphasising out that one cannot catch the infection from the vaccination - that is a myth.
'I always say that you should vaccinate in October or November [...]. However, because the elderly do not carry the protection long, they should be vaccinated last, just before the epidemic begins. However, the real solution is to introduce altruistic vaccination, where you vaccinate the young to protect the elderly.' At the moment, up to 65 per cent of the elderly are vaccinated, and the majority the rarely catch flu, except when their grandchildren visit.
There are two ways in which the virus mutates. Usually, the virus will mutate by small increments year-to-year, so that in a healthy young person, once he or she has caught influenza, protection should last for three or four years, or even longer. Occasionally, the virus can change to a completely new type, as happened with the 1918 'Spanish flu'. The H3N8 strain mutated into the H1N1 strain, which spread around the world in two waves over two years. Figures are difficult to estimate, but range from 50 to 100 million deaths. Huge movements of troops at the end of the First World War contributed to the spread of the disease.
Documents the professor has collected show that in the US, in Philadelphia, 0.7 per cent of the population died in a ten-week period. In Boston, 5.7 per cent of 20-30 year-olds died. This rise corresponds to a death-rate 178 times the usual figure. 'We can never avoid that. We need to move from a major disaster to a minor catastrophe.'
Should an epidemic on a similar scale happen again, the increase in population , from 1.8 billion to 6.4 billion means that the number of dead would be far greater, especially as the population increase is taking place in developing nations, which often do not have the benefit of vaccinations. 'It is not necessary to make people panic, but to put your head in the sand is not advisable either,' he said.
Professor Van Ranst gave an overview of successive epidemics, which have been successively less lethal and occurring every ten years or so. Interestingly, the professor believes that the 'Russian flu' of 1977 was most likely spread because of a lab accident. He believes this because of the uncanny similarity of the Russian flu virus to another H1N1 virus from the 1950s. Such small genetic differences over that 20-year time period would seem highly unlikely in such an active virus, unless it was the old strain, unchanged under lab investigation.
There has not been a large flu epidemic for some time, and avian flu is the current candidate, as it is impossible to predict. 'In chickens, they die quickly, with symptoms similar to those found in humans during the 1918 epidemic - the trachea spotted with blood, a kind of haemorrhagic fever,' he said.
'Entire flocks can die very quickly. Too quickly even for the bird to lay eggs. Their immune systems are overreacting to the disease. Such high mortality is an efficient system to eradicate the epidemic.' Bird flu is now spread over the migration 'flyways', and a fraction of birds carry the disease. One flyway covers all of Europe, so the virus is probably already distributed around Europe, although it is not yet an epidemic.
'People die of avian flu due to ignorance. Education will eradicate the problem. If people know not to interfere with dead birds, then the problem will go away. Now there have been 191 cases and 108 deaths. The number of fatalities is simply too high to spread the disease [as people are dying before passing it on]. If the figure starts to decrease, then we should start to worry.
'A pandemic could happen when human and avian flu strains combine. Some believe that there needs to be a recombination involving pigs. Most likely, if something like this happens, the virus will adapt in a human host, enabling it to be spread. We should not be worried, but we should be prepared. Vaccination coverage will increase to 33 per cent by 2010. But, these vaccines will cover only the EU, and not prevent a pandemic,' he said.
Professor Van Ranst wound up the talk with some sobering statistics. 'Some perspective is required. Measles kills 700,000 every year. Reactions to the Asian tsunami were very strong. We have a tsunami dying every week from malaria - two million people per year. Tuberculosis kills 2.5 million, and HIV three million. This is where the money should be going. Simply - we do not care enough about the countries where significant numbers of people die from diseases like malaria. This is why we have no malaria vaccine. Bird flu and SARS capture the headlines because of their novelty value.
'People should be protected, and this should be done through altruistic vaccination - where the benefit goes not to the person being vaccinated, but to someone else. In the 1960s and 1970s this was done in Japan, to impressive effect,' said Professor Van Ranst.
Altruistic vaccinations are the solution to the problem of flu. Some US states already apply this policy, but for different reasons - to protect children. Currently flu is low on the list, but should a pandemic become a reality, then altruistic vaccination is the only sensible option.