According to Britain’s Health Protection Agency, restricting air travel will have very little impact on the spread of a new flu pandemic. The study stresses the importance of having a vaccine ready and in good supply, as the only really effective weapon against a flu pandemic which could hit if the current H5N1 bird flu virus strain mutates.
Without a vaccine we will be at the mercy of the virulence of the mutated virus i.e. if we have no vaccine, let’s hope the mutated virus is not too powerful.
In this study researchers calculated how the 1968-69 flu pandemic spread by using a mathematical model. They then used the computer modelling to create different scenarios with a mutated H5N1 virus. If the H5N1 virus mutates so that it can easily spread from human-to-human, it will probably be the next flu pandemic.
Unless all air travel is immediately stopped, having restrictions will be of little value in delaying the spread of an epidemic, say the researchers. It would only be effective if absolutely all air travel were stopped as soon as the epidemic hit. Even if 99.9% of air travel were restricted right at the beginning of anoutbreak, it would only buy us an extra four months.
You can read about this study in the Public Library of Science Medicine.
The problem with creating a vaccine is that you have to know what the mutated virus will be like beforehand. It is not easy to predict. On the other hand, many scientists are now saying that even a vaccine which is not an exact match to the pandemic virus, but fairly close, would be a great help.
Travel restrictions and quarantine procedures did help stem the spread of SARS in 2003. However, flu can be spread from person to person before the infected person starts showing symptoms – you can be contagious before you even know you have the flu.
Screening people at airports for flu is not very effective. Trials have shown that this procedure only identifies 10% of infected people.
Scientists say it is only a question of time before the H5N1 bird flu virus strain mutates so that it is transmissible among humans. At the moment humans can catch it from birds, but not easily. It is even more difficult for a human to pass it on to another human. The main reason is that H5N1 has to get deep down into the lung to make someone ill. It infects the lower respiratory tract. Most flu viruses infect the upper respiratory tract. A person today, infected with H5N1, who coughs and sneezes hardly exhales any of the virus as it is so deep down.
For H5N1 to be able to infect humans easily it will need to infect the upper-respiratory tract – nearer the throat. To do this it will have to mutate. Then people will catch it more easily as it does not have to travel so far into the body. When someone coughs and/or sneezes more viruses will be exhaled, making that person more contagious.
The good news is that upper-respiratory tract infections are generally easier to treat than lower-respiratory tract infections. Therefore, we hope the mutated H5N1 virus strain would not be as deadly as it is now.
Public Library of Science Medicine
Written by: Christian Nordqvist
Editor: Medical News Today