Do we have to worry?
Bird flu of the virus type H5N8 has been found in the Netherlands. In 2003 and 2011 we had to deal with the bird flu. Ab Osterhaus, professor of virology and head of the Virology Department of the Erasmus Medical Center Rotterdam, answered five questions about bird flu.
1. What is bird flu?
“We have three forms of flu in humans. The ‘normal’ winter flu, we are then dealing with an influenza A or B virus. Bird flu: this flu is caused by influenza A viruses and can be transmitted from birds to humans. And the pandemic flu, a worldwide flu outbreak caused by an influenza A virus that spreads rapidly as it is passed from person to person.
Avian influenza or bird flu is the basis of all flu viruses. Influenza A probably originally only occurred in birds and not in mammals. The virus is characterized by the surface proteins H and N. We know of sixteen variants of H and nine of N. The human immune system focuses, by means of protective antibodies, mainly against the H and to a lesser extent against the N.
Influenza A viruses mainly affect migratory and waterfowl such as ducks and geese. They are therefore the main distributors of these viruses. So-called low pathogenic variants of these viruses occur in these birds. This means that they lead to few or no symptoms of disease in them. The virus resides in the gastrointestinal tract or respiratory tract, which facilitates environmental spread.
If H5 and H7 subtypes of these flu viruses are subsequently picked up by poultry, they can mutate into the so-called highly pathogenic form. This is a variant that does cause serious illness in poultry and very often leads to massive death. We called this bird flu in the past.”
2. Is an outbreak of concern?
“Free-range poultry farms are regularly screened by the government. The poultry is then examined for the presence of disease symptoms such as increased mortality and decline in egg production. If there are symptoms of disease, the poultry is tested for the presence of H5 and H7.
In the presence of low pathogenic H5 or H7, the company is culled as a preventive measure. In this way a possible outbreak with the mutated highly pathogenic viruses is prevented. In the case of a highly pathogenic bird flu virus, there is a calamity with large poultry deaths. Borders will then also be closed immediately and severe measures will be taken.”
3. What are the consequences for people?
“The consequences of the bird flu mainly concern the poultry trade, but there can also be consequences for public health. Human infection with the low pathogenic flu virus is almost non-existent, but the highly pathogenic virus can cause complaints, as in 2003.
Most bird flu virus infections cause mild flu symptoms and/or an eye infection in humans. Among the people who became ill in 2003, it was mainly the clearers and those directly involved. The vet who died in 2003 from bird flu, unlike the reapers, was not treated with an antiviral drug.”
4. How is the bird flu now?
“In 1997, our lab at Erasmus Mc, in Hong Kong, identified infection with the H5N1 virus for the first time. Since that time, more than 500 people have become seriously ill from infection with this subtype, mainly in South-East Asia, but also in the Middle East. More than half of the people have died shortly after the infection. In Indonesia and Egypt, for example, someone gets sick every week from the H5N1 virus.”
5. When should we start to worry?
“Of all people who become ill from the highly pathogenic H5N1 bird flu virus, about 60 percent die. That is a lot, especially when you consider that in the past ‘at most’ 1 percent of all infected people died from the Spanish flu (estimated worldwide as about 20 to 40 million people).
A pandemic outbreak by an H5N1 subtype virus could therefore have catastrophic consequences. That is why the World Health Organization (WHO) is urging governments to be prepared for an outbreak of H5N1 (or any other type of highly pathogenic bird flu virus) and to take appropriate action at the slightest indication. Given the seriousness of the possible consequences, these measures are absolutely not exaggerated.”
Situation 2014: H5N8
The highly contagious bird flu virus that has now been discovered on a chicken farm in Hekendorp is of the H5N8 type. The H5N8 variant has previously surfaced in China and South Korea, as well as Germany. It is not yet clear whether the virus has spread from Germany to the Netherlands. The H5N8 virus is only contagious if one comes into direct contact with infected animals. H5N8 is not transferable from person to person.
In theory, people can become infected through H5N8 – through intensive contact with chickens – but so far this has not happened.