Imprimir Republish

Edison Luiz Durigon

Edison Luiz Durigon: High-risk intimacy

Viruses causing respiratory diseases change from time to time and force a coexistence that is harmful to man, states virologist

eduardo cesarViruses, a word that sounds highly familiar to most people and since April, cloaked as A H1N1, have become daily figures, sometimes scandalously visible, in all of the world’s media, can still really intrigue the scientists who dedicate their lives to deciphering them. To start: are they live beings? No, they are not classified as live beings. When outside a cell, they are just a chemical. But within cells, they become infectious particles with enzymes and nucleotide sequences that allow them to replicate and behave like a living being. The person who explains their ambiguous and ambivalent nature in this way is Edison Luiz Durigon, aged 53, senior professor and head of the Virology Laboratory at the Microbiology Department of the Biomedical Sciences Institute at the University of São Paulo (USP). Another question: are there any viruses that are beneficial to humans, as there are bacteria that are fundamental for proper metabolism within Homo sapiens’s body? No, as far as we know, says Durigon. Not all viruses cause pathologies; there are some that remain inert for a whole life, but to date no benefits derived from them have been found.

As a result of the A H1N1 flu pandemic that began between last March and April in the Northern Hemisphere, and that is now spreading to the Southern Hemisphere, Professor Durigon has been facing these and other more pragmatic questions posed by physicians, journalists and other professionals that are trying to explain the origins, evolution and dangers of a disease initially called the swine flu. He seems to attend to this task with gusto. One of the most respected virologists in Brazil, and the coordinator of the VGDN Virus Genetic Diversity Network, set up in 2000 with FAPESP support, Durigon has been focusing, since the 1980’s, on researching viruses. First, his group pored over the rotaviruses that cause diarrhea, and he is certain that they contributed to a clear, lifesaving understanding of the fact that children’s diarrhea is caused primarily by viruses, rather than by bacteria. Then, in the 1990’s, he turned to viruses connected to respiratory problems, including the influenza ones. The progress achieved in this area enabled him to undertake a number of incursions throughout the country, in the current decade, to monitor, among migratory birds, the risk of the so-called avian flu arriving in Brazil.

In this interview, Edison Durigon, who did his post-doctoral work at the Center for Disease Control (CDC) in Atlanta, USA, talks about the A H1N1, the flu caused by it, and many other viruses, with their mutations, uncertainties and threats.

What are the specificities of the swine flu virus, the A H1N1, and what sets it apart from  other types of influenza viruses?
“It’s different. We have two viruses that have been going around the human population for quite some time: the H3N2 and the H1N1. Both descend from the 1918 Spanish flu virus. They have modified gradually, becoming weaker in man and causing the so-called seasonal flu. Every year we have flu worldwide, caused by these two types of viruses. Other than these, which are of the influenza A kind, there are others that belong to the influenza B kind and that have never caused any pandemic. Therefore, in public health terms, one is always concerned about the influenza A viruses. ”

Are there differences in terms of seriousness between the A and the B kinds?
“There are two types of influenza A viruses. One that has the same seriousness as the B kind, with low pathogenicity, and another that has high pathogenicity and is very dangerous. It replicates far faster, causes pulmonary hemorrhaging and can infect other organs. This is what happened in 1918 with the H1N1. It came straight from birds to man and caused a pandemic known as the Spanish flu in which at least 50 million people perished.?

Wasn’t the 1957 Asian flu caused by the same virus?
“No, it was caused by a descendent of it, a mixture including viruses from other animals, generally from birds and swine. Birds are a natural flu virus reservoir; man gets contaminated and, over time, adapts. The Spanish flu mortality was high because it was caused by a high pathogenicity virus, which became attenuated naturally, developing low pathogenicity. It is the one that is still amongst us today, after a lot of readjustments. It joined together with swine flu, then again with bird flu, generated H3N2, then went back to H1N1…”

How do we know that the first time H1N1 migrated straight from birds to man was in 1918? Is it possible that there had been several similar flu episodes before?
“The 1918 flu is the first documented one. There are, of course, narratives about severe flu epidemics long before, 100, 200, 300 years ago. But we don’t know what already went around. However, from 1918 to our days, we have narratives, serum from people who got ill at the time, and there are still people alive who remember what happened and whose blood we managed to examine, to show the virus that caused the epidemic.”

In other words, there is sure empirical proof.
“Very sure. Now, the virus causing the current flu is a combination of four viruses: the swine virus, the human virus, and the bird virus; regarding the swine one, there are two strains: the H1N1 that is normal in swine in the Americas, called the American strain, and the H1N1 that goes around Eurasia, known as the Eurasian strain. Both are called swine H1N1, but they are genetically different. Therefore, the current swine flu that attacks humans is a mixture of these four: two swine strains – the American and the Eurasian ones, a human one and a bird one. In 2005, in the United States, a virus was isolated from a 17 year old young man who had had serious flu. They realized that it was a new virus containing a mixture of another three: American swine influenza, human influenza and bird influenza. But they only isolated this from one person, there were no other cases. It is believed that this three-virus mixture evolved into the current four-virus one.”

So can we say that the current flu derives from virus changes taking place since at least 2005?
“In the United States, there are reports that the swine H1N1 virus circulated in the seasonal flu epidemic last year. At present, we are testing samples here drawn from children hospitalized at Santa Casa de São Paulo in 2008 and we have strong evidence that the H1N1 of the so-called swine flu was already amongst us last year. An Australian team published a notice stating that the virus may be similar to one that was already going around in 2007.”

If you do indeed indentify the swine H1N1 virus among these children in 2008, would you say that these were isolated cases?
“One can’t tell. In Brazil, it is uncommon to identify flu viruses. We have three flu reference centers: the Adolfo Lutz Institute, in São Paulo; Fiocruz, the Oswaldo Cruz Foundation, in Rio de Janeiro; and the Evandro Chagas Institute, in Belem. When an epidemic starts, the state laboratories do a quick immunofluorescence test to check whether it is influenza A or B. This is what we are able to do and these are the data we have. A rather small sample of this material – from Adolfo Lutz, Fiocruz and Evandro Chagas – goes to the CDC for them to identify the type. And every year they warn us which kind of virus is circulating in São Paulo, Rio de Janeiro and Belem. Even here at USP, where, since 1995, we routinely collect, at our University Hospital, samples from the children hospitalized with bronchiolitis and acute illnesses and test for influenza, we stop at this because, for a doctor, it is enough to know whether or not the disease is influenza. When the swine H1N1 virus appeared, a new diagnostic test was implemented, both at the three institutes I mentioned and in private-sector labs. And we also do tests here, at ICB.”

Why do you work mainly with children?
“We have efficient pediatrics at the University Hospital and children are of academic interest. The same is true of pediatrics in the Santa Casa hospital. Note that we use the word flu generically. Flu isn’t only caused by influenza A or B, there are other viruses, such as the respiratory synsytial virus, the parainfluenza virus, the metapneumovirus, the adenovirus. All of these cause a series of symptoms that make it difficult for a physician to figure out what the disease is. They are unable to find out and there is nowhere they can turn to in order to find out. When we have flu, the doctor tells us to come back if we get worse because it can turn into pneumonia. All the deaths we have nowadays are due to pneumonia.”

“Almost all. There may be an occasional death from other complications, but the low pathogenicity influenza virus on its own is not a killer – what kills are the complications. The virus can cause an inflammation of the lungs that predisposes them to become infected by bacteria. Many people’s throats are colonized by pneumococci, so that when they get flu, these bacteria can migrate to the lungs and cause fatal pneumonia if it isn’t treated with antibiotics. Sometimes, the person has flu symptoms and doesn’t go to the doctor thinking everything is OK. If that person did go, perhaps an X-ray might reveal the seriousness of the problem, but hospitalization and medication could fix all of it. Look at the cases of death from swine flu in Osasco. Had it been in 2008, the four people hospitalized with flu symptoms and pneumonia would also have died, because they were at a bad stage of the disease, but the death certificates would state, as cause of death, pneumonia caused by streptococci, and we wouldn’t have learned about the swine flu cases there. As happened this year, when there’s a flu that is being heavily publicized in the media, as soon as patients with severe respiratory symptoms arrive, samples are collected for analysis. In the Osasco case, it was proven that it was swine flu when the first person had already died.”

So actually, the deaths occur because of pneumonia.
“This flu isn’t causing more deaths that the others. To the contrary, fewer people are dying.”

Going back to the origin of H1N1: does the fact that it is a combination of four other viruses make it more complex, whether in regard to understanding its structure, or producing a vaccine?
“Yes, of course. Nobody knows yet to what extent the seasonal flu vaccine protects against the new virus. Because it is new, it will infect a lot more people because nobody has antibodies against it. There is a theory that because it is very similar to the H1N1 that went around in 1978, during the Russian flu, those who were infected then don’t catch it or only get it mildly. Which is why we aren’t seeing cases in people older than 50 or among the elderly. Those who are affected the most are young adults of up to 35 years of age, pregnant women and young children.”

The British journal The Lancet published, in the last week of July, a study covering 34 cases of the A H1N1 flu among pregnant women from April to May, and six deaths of pregnant women from April to June. In other words, out of 45 deaths examined during this period, 6 were of pregnant women. As the researchers estimated that pregnant women account for 1% of the US population, these 6 deaths represent a higher death rate than the standard for other adults.
“Everything is still very new and the data are still being produced. The fact that the virus is more complex causes it to infect more people at the same time. Flu generally occurs during winter. However, what we witnessed in the Northern Hemisphere is a flu epidemic that was not in winter – when it was meant to be dying out, it appeared again, because it infected a lot of people who were susceptible to the virus. In Brazil, the flu should come to an end in August, but from the look of things, it’s just beginning. And, if it follows the same pattern as in the Northern Hemisphere, it will remain with us until October. It is only now that the cases started rising in number.”

Regarding the virus’s mutation, is this a concern only for 2010?
“Yes, because we know the current virus a bit better. We know it has low pathogenicity and that it isn’t going to behave very differently from the seasonal flu virus. Swine flu has a lower mortality rate than the regular flu, but one cannot say that it is less pathogenic.”

In Brazil, it’s considered normal for people to go to work with flu. Shouldn’t it be the opposite?
“Actually, going to work with flu shows lack of respect for others. People with flu spread the virus to everyone. One individual contaminates about 10% of the group with whom he or she works. These 10% will contaminate another 10%. In a short while, everybody will be infected. But if Brazilians don’t turn up at work because they have flu, their bosses think they’re lazy. The ideal thing is to stay at home. A child with flu should not go to school, even if he or she is feeling well, because this child is still eliminating the virus.”

How long does it take to get rid of the virus?
“As long as seven days, when you have flu. Transmission by air takes place when we sneeze. But this is not the main form of contagion. As we eliminate a lot of secretion, it’s inevitable to put our hands on our nose, to scratch ourselves, put fingers in one’s mouth. It’s a habit we have, as primates, that is very difficult to control and that favors greater transmission. And we’re always touching things when we go to work, study, meeting people. The ideal thing would be to stay at home for 10 or 15 days, until one is completely cured.”

In the work that your team did in 2005, capturing birds in the Amazon Forest, the aim was to look for H5N1 in the migratory birds. Was anything found?
“We found a fair amount of influenza among the birds, but not H5N1, which was the great fear of the Ministries of Health and of Agriculture, because it is a highly dangerous virus both for people and for birds. It kills more than 50% of the people it infects. But it is only transmitted from birds to humans, not from person to person. What causes a virus to infect man is the virus’s contact with superficial cells, like the cells of the nose, the mouth… For the virus and infection to adhere, the cell has to have a specific receptor for the virus in question. The spicula on the surface of the swine flu virus are recognized by the specific receptor in the cells, in this case sialic acid, and a certain conformation of the spicula enables the virus-cell fit. The avian virus does not fit well into the human cell because of its conformation. To date, the avian infections occurred through direct contact with the birds secretions, causing the person to receive a large quantity of the viruses that reached all the way into the lower bronchial or lung cells.

Are there still fears about this type of transmission regarding avian flu?
“Oh yes! The conformation depends on only three mutations in the virus’s genome, and one has already occurred. Two to go. We have 486 cases of avian influenza cases, with 260 deaths [June data] in Asia and in Europe. It’s a lot, more than 50%. In China, this figure is almost 100%. This year, they had seven cases with five deaths.”

In the case of avian flu, there was the possibility of developing an effective vaccine, but this didn’t happen.
“As the virus hasn’t yet undergone the mutation that is required for it to become transferable from one person to the next, there’s no point in making a vaccine for the current flu. It won’t work after the mutation has taken place. It’s similar to the swine H1N1 case. In the seasonal flu vaccine people took this year, there was H1N1, but it’s not 100% effective against the swine flu, although it does, perhaps, protect some people.”

So we have yet another problem: the mutation that the A H1N1 virus may undergo next year. In other words, vaccines would have to foresee this mutation.
“There are some vaccines made for this swine H1N1 that should be in the market in September. The major private-sector labs are running because the flu epidemic is about to start again in the Northern Hemisphere more or less in October and November and everybody wants to have the vaccine in hand before that. But they are still being made to fight the virus’s current version. One cannot make a vaccine against the next one without knowing what the mutation is going to be like.”

If the avian flu virus mutates, can a vaccine be made quickly?
“One of everyone’s major fears when the swine H1N1 virus appeared was that it might get into China, because there they’re still getting cases of H5N1. There’d be the risk of the same patient catching both viruses and generating a mutation. China took far stricter measures than the rest of the world, such as keeping people from entering the country or quarantining them. But it’s very difficult to create a barrier for a virus. They have a lot of cases of swine flu and a few of avian flu. China is going to be our big problem, because H1N1 has already been mixed up on all sides. The risk of this happening again is not small.”

It seems that this is the first time it’s possible to follow the emergence of a new virus from the start. Isn’t this an advantage?
“Yes, of course. But everybody’s very frightened, including the doctors at hospitals here in São Paulo. If a person turns up with severe flu, does the test and it indicates swine H1N1, they have to isolate the patient. But where? If you turn up with some other problem, the doctors are unable to hospitalize you because the hospital’s packed with flu patients.”

But the Adolfo Lutz Institute could help and produce results within a few hours, instead of seven days.
“The Adolfo Lutz institute alone can’t handle the tests for all of Brazil, for the entire state or the entire city. What must be done is to distribute the tests among all labs, whether they are governmental or from the private sector. The United States is the country for which we have the largest amount of data, because when the epidemic began, in March, the government produced diagnostic kits and distributed them to all the American labs that were competent to use them, whether they belonged to the public or the private sector. For those that lacked the equipment, the Center for Disease Control acquired it and distributed it. In any American state there are labs that can produce a diagnosis on the same day. Our University Hospital has an excellent lab and could be making diagnoses. The patient could turn up suffering from the symptoms, do the test, which produces a result in three hours and, if he or she had the virus, promptly take the right medication, which is oseltamivir, whose commercial name is Tamiflu. It’s a drug that only works if it’s taken in the first 72 hours. The problem is that there isn’t enough Tamiflu.”

Why isn’t there enough Tamiflu?
“The manufacturers are Roche laboratories. It just so happens that worldwide demand has become so great that they can’t make enough of it. This is a very specific drug and Brazil has never used a lot of Tamiflu because patients normally turn up at the hospitals more than three days after they got the infection and by then the drug is useless. Furthermore, if the doctor isn’t sure the patient is suffering from influenza, there’s no point in prescribing this drug.”

How can the population know whether it has swine H1N1 or seasonal influenza?
“There’s no way to now. Not even the doctors know. The flu symptoms are the same for several viruses.”

And what about the so-called winter colds, when people don’t run a fever?
“This is another type of virus, called rhinovirus. The symptoms are a runny nose, a bit of trouble breathing, feeling unwell, but no temperature. Influenza normally produces a high temperature along with the other symptoms. Of the tests we have been conducting for the University Hospital, almost 100% have been swine H1N1. We are having neither seasonal H1N1 nor H3N2. This applies to the last two weeks in July. In June, the ratios were 30% and 50%. The time of the H3N2 and of the H1N1 seasonal viruses begins in May and lasts up to early August; then they disappear. This is not to say that there’s no flu throughout the year, but it peaks in the June-August period, when the two viruses go around the most. This year, they went around along with swine H1N1 and stopped going around in keeping with the seasonal trend. However, the transmission of the swine virus began now. That is why from now on we can expect to have only one type of virus, the swine one. The same happened in other countries.”

Up until when will the H1N1 dominate this year?
“Until October, I believe. Certainly during August and September.”

And during this period, can people learn more about it to try and avoid it?
“I think so. People are scared, but there isn’t a major neurosis, with everyone walking around in masks. In Mexico, for instance, they got desperate and put masks on the population. But wearing them didn’t reduce the epidemic, although they say it did. Furthermore, one must know how to use a mask. In a flight from Porto Alegre to here I saw a passenger who took the mask off to eat and laid it on the seat next to him, on the armrest on which people put their hand. What’s the use? Washing one’s hands helps a lot, it’s one of the best measures there are. But it’s hard doing it all the time on a daily basis, because we’re always touching objects that other people have touched. In sum, washing one’s hands helps, but the virus will continue to be transmitted, causing 10% of the infections; certain severe cases will continue to occur as well as some deaths.”

What is the work of your laboratory like regarding the investigation on influenza in migratory birds?
“In 2000, our group set up a project with FAPESP’s aid, the Virus Genetic Diversity Network (VGDN) or Virus Network; I was one of its coordinators. We studied several viruses such as the HIV and hepatitis C ones, the synsytial respiratory virus, and the hantavirus – which is highly pathogenic – among others. We set up a field team to go to the Amazon Region to capture migratory birds.”

You went on safari looking for viruses?
“Exactly. We held several expeditions in order to spend one month in several states. It was a project designed to monitor the possibility of H5N1, the avian influenza virus, coming into Brazil. Nothing was being done at the time. The first expedition took place in 2005. Prior to that, we had to create infrastructure for this, starting in 2001, such as setting up a maximum security lab, the NB3+, plus ensuring safe transportation, in line with all international safety rules. One couldn’t collect viruses in the Amazon Region from migratory birds and then bring them to an area with 20 million inhabitants in an unsafe manner. That would have been hugely irresponsible.”

Did the Virus Network establish other labs?
“We set up six of them in the State of São Paulo just for diagnosing these viruses. Today, they are all in operation and can carry out the H1N1 tests. During this time, some epidemics arose that frightened everyone, such as Sars [Severe acute respiratory syndrome]. When this appeared in 2003, we only had my secure lab to work on the Sars coronavirus. At the time, I got the data about everything that was going on in the world and took it to Professor José Fernando Perez, FAPESP’s scientific director at the time. I told him that we had a network to study viruses, but if Sars got to Brazil we wouldn’t have enough labs for the diagnosis. I then suggested creating at least six secure labs capable of handling the samples. I brought together people who were competent to do this within the Virus Network and we created the labs.”

Where are these labs located?
“We have the ICB/USP Virology Laboratory, the Adolfo Lutz one, one in the Tropical Medicine Institute at USP, under Professor Claudio Pannuti, one in the town of Botucatu, under Professor João Candeias, one at the Medical School of Ribeirão Preto, under Professor Eurico Arruda, and the Unesp one, in the São José do Rio Preto campus, under Professor Paula Raw. The six labs are equipped with the physical structure of negative pressure required to keep the virus from escaping, with protection for their neighbors and for those who work within them, with maximum security flow chambers and equipment to do quick influenza identification tests.”

Who coordinated the Virus Network?
“There were  three of us: Professors Paulo Zanotto, Eduardo Massad and myself. The project came to an end in 2007, by which time we had 22 labs in the network. Today, they continue to be active and equipped, but no longer work within a network. We are now trying to reestablish the network of the six maximum security labs and we want to set up another six, not of the maximum security kind, but capable of handling the influenza viruses. When Sars appeared in the United States, they created, in each state, a network with labs of this sort.”

How long have you been doing work on viruses?
“Since 1980. We started a major study in 1981 with the rotavirus diarrhea virus. Doctors used to think that most cases were caused by bacteria. We carried out several studies with Professor José Alberto Neves Candeias, who pioneered this type of work. We were his followers. Thanks to these studies, carried out with the University Hospital and the Clinicas Hospital, we managed to reduce diarrhea.”

The substantial drop in São Paulo child mortality reflects this.
“Undoubtedly. Previously, in the 1980’s, a child would come along with diarrhea, the physician would prescribe an antibiotic for the child and send the kid home. These children came from underprivileged families; the mother had to work the whole day and the child would end up not taking the medication. By the time the kid came back to the hospital, it was dehydrated already and died. We showed that the illness was generally caused by a virus rather than by bacteria. The physicians also changed their conduct and started hospitalizing the children who turned up with diarrhea. This generated a lot of confusion at the time, because the parents couldn’t stay with the kids, but mortality plummeted.”

Why was it necessary to hospitalize the children?
“Because the children, once they went home, weren’t properly hydrated, but they were in hospital. When we saw that hospitalization worked, the social service group started training the mothers to use home-made hydrating mixes. Today this is no longer necessary as mothers now know how to do this. There was work done on this worldwide, through World Health Organization campaigns, Unicef campaigns and, in Brazil, through the Pastoral da Criança child-welfare oriented organization as well. Diarrhea decreased substantially in all countries. In the 1990’s, the chief problem became mortality due to virus-based respiratory diseases. That is why we changed the lab’s focus. We work with influenza and the other respiratory viruses, taking into account the possibility of avian flu entering Brazil.”

The migratory birds travel from the Northern Hemisphere to the Southern Hemisphere and vice-versa every year. Is there any prevalence of viruses coming more from one side than from the other?
“That is one of the things we study. The Americans who research this say that the birds get infected in Brazil and carry the virus there. Since last year, we’ve been running a new project on Canelas island, which lies to the north of the island of Marajó, where birds stop on their way from the Northern Hemisphere, from October to December, before they go south. From February to April they go back north and stop in Canelas again. We catch the birds when they arrive and when they leave, to see how many arrive infected and how many go back infected. We work with together with a group under Professor Severino Mendes, from the Rural Federal University of Pernambuco.”

And what do you think?
“I believe that they arrive from the Northern Hemisphere infected. But our figures are still very preliminary.”

Is the relation between viruses and humans always pathological?
“Not always. But it’s not like it is with bacteria, which form flora that is normal in man and are not necessarily bad. There isn’t a single virus that man needs. But there are inert viruses, which stay with you but don’t make you ill. Some are naturally eliminated over time. Some become integrated, especially the herpes viruses. We know some of them, such as the one that appears around the lips, herpes 1 and 2, but there are others, such as herpes 6 and herpes 7 that people may carry for their entire life without ever being aware of it. Regarding the man-influenza relation, the Chinese were the ones that started domesticating birds and brought this virus to man.”

Is molecular biology your virus study tool?
“It’s our chief weapon. With it, we can detect viruses faster, we have greater sensitivity and we can gain more in-depth knowledge about the evolution of viruses. Sometimes one has to return to classic methods. Secretions from a sick patient contain a huge amount of viruses, enough for us to work with. But a healthy migratory bird eliminates very few viruses and I can only detect them by using PCR, a molecular technique, but there isn’t enough material to sequence and to conduct other studies. So then we need to use classic culture means. We still use embryonic eggs and cell cultures.”

Lastly, an interesting question: is a virus a living being?
“It is not classified as such. It is considered an infectious particle with two important characteristics. When it is outside the cell it is a chemical, but within the cell it behaves like a living being; it has enzymes and nucleotide sequences that allow it to replicate and behave as if it were a living being.”