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Public Health

Plan of war against the virus

Brazil is getting ready to face bird flu, while science is still trying to foresee the spectrum of the pandemic

Brazil has taken new steps in its preparation for facing an epidemic of bird flu. By May, the country will have six laboratories capable of diagnosing, in a period of just three hours, the contamination of birds by the H5N1 virus. The National Livestock Husbandry Laboratories (Lanagros) entrusted with the task are in the cities of Belém , in the state of Pará, Concórdia, in Santa Catarina, Recife, in the state of Pernambuco, Pedro Leopoldo, in Minas Gerais, Porto Alegre, in Rio Grande do Sul and Campinas, in the state of São Paulo, currently the only equipped one. The investment is R$ 39 million and will imply the training of 1,700 technicians. “It is an important measure for detecting focuses of the disease promptly. To have an idea, some countries affected by bird flu in Europe have to send samples for analysis in the United Kingdom”, says infectologist Vicente Amato Neto, a professor from the School of Medicine of the University of São Paulo (FMUSP). Five other laboratories will gain equipment for molecular diagnosis by PCR, or polymerase chain reaction, which analyzes the DNA of the virus with a sensitivity of 98%. The measure is part of a contingency plan drawn up by the Ministry of Agriculture, Livestock and Supply.

On another front, the Butantan Institute, of São Paulo, announced that in June it will begin testing the vaccine against bird flu developed from strains of the H5N1 sent by the World Health Organization (WHO). “We are going to test it directly on human beings, since the vaccine is not made with a living virus. We want to know whether the vaccine is capable of setting off the production of antibodies”, says Jarbas Barbosa, the secretary for Surveillance in Health at the Ministry of Health. The virus has now caused the death and the sacrifice of thousands of birds on the Asian continent since 2003. In the last few months, panic was disseminated with the identification of contaminated birds in several countries of Europe, from Poland to Denmark. The frontiers of the disease have also advanced over Africa, with cases in Nigeria, and in the Middle East, reaching Afghanistan and Azerbaijan. Over 200 human beings have contracted the illness. A little over half of them have died, the majority in Asia, the cradle of the virus.

Sacrifice
The way it is transmitted today – only from birds to humans – bird flu means more an economic problem, for the mass sacrifice of contaminated birds, than a public health problem. But, for the WHO, it may be just a question of time for the virus to undergo a mutation and begin to be transmitted from human being to human being. This would happen, should a person be infected with bird flu and with a common flu, at the same time, which could create a new kind of virus capable of spreading amongst men. According to Jarbas Barbosa, if the alteration in the virus is a small one, Brazil will be better prepared to quickly produce an effective immunizing agent. To start with, 20 thousand doses will be manufactured, but the Ministry of Health plans to form a stock to make it possible to vaccinate people who may have come into contact with the virus or with contaminated individuals.

These measures add to others taken since the end of 2005. Following the recommendations of the WHO, Brazil has drawn up strategies for fighting it on several flanks. The first of them consists of trying to prevent the virus from coming in. To do so, the importation of ornamental birds has been prohibited, and the controls at the ports and airports have been intensified to prevent the entry of poultry products of a suspicious origin. The second strategy is to identify focuses of the virus immediately after its arrival, to prevent the illness from spreading. The government is monitoring nine routes of migratory birds in the states of Rio Grande do Sul, Paraná, Mato Grosso do Sul, Bahia, Pernambuco, Rio Grande do Norte, Maranhão, Pará and Amapá, following joint work carried out by the Ministry of Agriculture, Ibama and universities. Hosts of the virus, migratory birds are regarded as the main factor for the dissemination of the H5N1. In April, the migration cycle of these birds ends.

At the birthplace
In the event of there being contagion from birds to human beings, the strategy is to isolate the area, treat the sick with antivirals, and vaccinate the surrounding population. Besides sponsoring the development of the vaccine at Butantan, the government has bought 9 million doses of the antiviral Oseltamivir, the commercial name of which is Tamiflu, the most efficient in the treatment of bird flu.

From March 6 to 8, 70 specialists from all over the world, brought together on the initiative of the WHO, discussed the logistics, the surveillance and other public health measures that would be necessary to face up to the disease. Generally speaking, the strategy of containment was reaffirmed, which proposes a quarantine in the affected areas and the mass use of the Tamiflu antiviral. A flu pandemic has never been successfully limited in this way, but the WHO believes that there is a chance of containing it in the birthplace.  “Although controlling a pandemic at its source is something that has never been tried, the evidence is growing that this may be possible”, said the WHO, through a note. It so happens that the first outbreak of H5N1, recorded in 1997 in Hong Kong, was successfully contained with the slaughter of 1.5 million birds raised in the country. Theoretical models suggest that it is plausible to contain the pandemic, provided there are antivirus precautions that reach humans in a period of a few days after its mutation. And if it doesn’t work? “It may be that the efforts in containment just reduce the speed of the dissemination of the pandemic”, said Margaret Chan, the WHO’s assistant director for transmissible diseases. “But even so it will mean that we gain time for starting the production of vaccines.”

Whether these measures will be timid, sufficient or exaggerated, only time will be able to say. “The strategy is underpinned by common sense, because there is no scientific data making it possible to draw up adequate measures”, explains Eduardo Massad, a professor of Medical Information Technology at FMUSP. Massad recalls, in the first place, that there are doubts about the capacity of the H5N1 virus for undergoing mutations and disseminating itself amongst humans. “The great flu pandemics were caused by an influenza virus of the H1, H2 and H3 types, and they alternate every 68 years. By this account, the next pandemic would be caused by a virus of the H2 type in 2025”, he explains. Should mutation be made viable, says Massad, it would be necessary to get to know the intensity of its transmission. “We can draw up scenarios. For example: if the intensity is repeated of the Spanish flu, which killed 40 million persons and was the biggest to have been heard about, it would be necessary to immunize at least 80% of the population to prevent a pandemic. That is to say, at least 130 million Brazilians would need to be vaccinated. But if this intensity were like Asian flu, which happened in 1957, 40% of the population would have to be vaccinated”, he claims. The International Monetary Fund (IMF) is also forecasting scenarios. It reckons that the most affected nations may suffer losses of up to 25% of their Gross Domestic Product.

Massad’s conclusion is that it is not possible either to praise or to criticize what the authorities are doing. “They are doing what can be done in the current circumstances.” Massad is concluding a work about the incidence of the Spanish flu in the city of São Paulo, which corroborates the thesis that Europe, destroyed by the First World War, was an ideal stage for the dissemination of the disease. He observed that the lethality of the disease in Europe was three times higher than that seen in the capital of São Paulo, which, in spite of the sanitary conditions, did not display the open wounds of a great armed conflict.

The mobilization for facing up to bird flu in Brazil and in the world finds rare parallels in the history of emergent diseases. As the mutation that may be able to unleash a pandemic has not yet materialized, countries are gaining time to prepare themselves. That did not happen, for example, with the 2003 outbreak of the Severe Acute Respiratory Syndrome (SARS), which, when it was detected, had already been disseminated over various countries. With regard to the H5N1, the American continent may be in a privileged situation, as it has not registered any case yet. “But the migrations that took the virus to Europe may also go to North America, and from there to Brazil”, says virologist Edison Durigon, a professor from the Biomedical Sciences Institute (ICB) at USP.

At least one loss from the flu is now already very tangible in Brazil and is hitting poultry producers. The fear of the disease has led to a fall in poultry consumption in several countries, although contagion is not possible through the ingestion of cooked meat. With this, Brazilian exports in January suffered a fall of 13%. The price of the products has depreciated 16% since December.

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