In late May the team of virologist Terezinha Maria de Paiva, from the Adolfo Lutz Institute in São Paulo, advised that they had isolated the first swine flu virus from a Brazilian. The patient was a 26-year old man who was suffering from the flu’s symptoms after a trip to Mexico and was hospitalized on April 24 at the Emilio Ribas Institute. The case of this patient, who has already been released from hospital and is doing well, was the first one to be confirmed in Sao Paulo.
Molecular biologist Claudio Sacchi analyzed the patient’s samples of throat and nose secretion and confirmed that they contained genetic material of the influenza A (H1N1) virus, which causes the so-called swine flu. The variety found here was the same as the one that gave rise to the swine flu epidemic this year and that, up to May 26, had affected 12.9 thousand people in 46 countries and caused 92 deaths. The fast increase in the number of cases and the ease with which the virus is transmitted between humans led the World Health Organization (WHO) to issue warnings about the risk of a pandemic.
After identification of the virus, Terezinha obtained several copies after cultivating it for four days in the lab, using canine kidney cells. At the electronic microscopy section of the Adolfo Lutz institute, Marli Ueda and Jonas Kisielius identified a number of samples of the virus at the very first observation and were surprised by the large number of copies they found – in some of the images, they appeared to be grouped together, as if they were in a nest.
The prompt identification of the virus shows that H1N1, which primarily infects people through the upper breathing system, reproduces fast in mammal cells – which may include humans. According to Terezinha, sometimes it is difficult to make the virus reproduce within a lab and to observe it under a microscope, as this depends on the amount found within cells. “Generally, we only manage to isolate the virus in some 15% of the samples of patients with flu symptoms that we analyze every year,” she tells us. ‘We obtained the H1N1 at the very first observation.”
Around the world
Isolating the virus is fundamental to learn in detail about the variety that is going round this country. Under the coordination of Cecília Simões Santos, the Adolfo Lutz team was also planning to start the genetic sequencing of the Brazilian H1N1 in May and to compare it with the virus in other countries. This will enable us to learn to what extent the virus has already differentiated itself from the virus in other parts of the world, and how to plan a vaccine.
There are three known types of influenza virus: A, B and C. Of these, A is the most common and also the one that causes major epidemics. Every year, different varieties of influenza A circulate around the world. They are classified in accordance with two proteins on their surface – hemagglutinin (the H in the virus’s name), which the virus uses to stick to the cells of one’s respiratory airways; and neuraminidase, the N, which helps the virus leave one infected cell and invade another healthy cell.
This is not the first time that this virus has caused flu in humans. In 1918, a H1N1 variety that came from birds caused a global epidemic knows as Spanish flu, which killed 60 million people. Over the last three decades, less lethal variants of the virus, which seem to have been transmitted initially from people to pigs, have started infecting humans again, causing occasional outbreaks with few deaths. Some swine flu variants were even found in Brazil, where between 1976 and 1979 virologist Sueko Takimoto, from the Adolfo Lutz Institute, identified cases of flu caused by H1N1 among elderly people in the city of São Paulo.
In the Morbidity and Mortality Weekly Report of May 21, researchers from the CDC, the Centers for Disease Control and Prevention in the United States, found that people over 60 had some immunity against H1N1. One third of them have antibodies than can deactivate the virus – this percentage is lower than 10% among younger adults. The results help to explain the profile of the current epidemic, which tends to affect young people more severely, rather than the elderly, as is the case with common flu.
The good news is that, for the time being, the current epidemic seems to be less lethal than the previous ones. Seven people die out of every group of one thousand infected individuals. This rate (0.7%) is slightly higher than that of common or seasonal flu, which kills five people out of every thousand (0.5%). In the bird flu epidemic, this percentage was as high as 20%. Though it is relatively low, swine flu mortality could take a huge toll of lives if the virus spreads further: seasonal flu, which is less lethal, kills 500 thousand people a year. “With the onset of winter, the attention of international authorities will turn to the Southern Hemisphere, where the annual flu season is about to begin,” comments Terezinha.
In Brazil, the Butantan Institute is waiting for WHO to determine the varieties of the virus that should be included in the vaccine and the level of protection that it will provide. “As soon as the sample appears, the institute should start making the vaccine against H1N1,” states physician Isaias Raw, president of the Butantan Institute Foundation. Between 100 thousand to 1 million doses should be enough to avoid having the swine flu spread in the country, should the epidemic continue to progress. At first, these doses would be earmarked for the main points of entry into Brazil, such as ports and airports. “When a case is identified,” says Raw, “only those who had contact with the sick person will be vaccinated.” However, for as long as the vaccine does not materialize, the best way to remain virus-free is to adopt basic hygiene measures, such as discarding used handkerchiefs, keeping one’s hands clean, and keeping environments well aired.Republish