Flu A arrived

In February 1982, an outbreak ofswine fluin the state of Nevada (USA) he killed a four-year-old girl. The researchers feared aepidemicthat finally did not occur. Thevirusthat was isolated from the little girl turned out to be very similar to another that in 1976 had caused one of the most important epidemiological alarms in the history of the country. The viral agent killed a military man in Fort Dix (New Jersey) and infected 200 cadets. The alarm unleashed was such that the government of President Gerald Ford initiated a program that cost 135 million dollars to vaccinate more than 40 million Americans. The measure had to be suspended, since the administration of the drug was statistically related to a paralyzing disease called Guillain-Barré syndrome. Vaccine batches were destroyed, but the threat offlu? also calledinfluenza? did not disappear. Between December 2005 and February 2009, 12 more cases were recorded in the United States.

History repeats itself with many of the pathogens that infect animal populations, be they pigs, birds, or genets. They are always there, lurking, ready to leap into human populations at the slightest opportunity. Swine flu, whose virus is transmitted through the air, is one more case. As the consumption of pork meat does not imply any risk of transmission, to eliminate from its name references that affect the meat industries, it has been renamed influenza A. The crisis, which took shape in Mexico last April, dates back to the past March 18, when the authorities observed an increase in influenza cases and thought they were seeing seasonal episodes of the conventional one.

According to the medical journalThe Lancet, thefirst confirmed casein people it occurred inCalifornia, when experts from the Centers for Disease Control in Atlanta (CDC) found the presence of the virus that causes it, H1N1, in two individuals. It was April 21. Four days later, Mexican authorities announced that they had detected the same germ. The whirlwind of scared people, empty schools and masks on the street are already familiar to us.

The world has recently faced several epidemic outbreaks, such as atypical pneumonia or acute severe respiratory syndrome (SARS), a serious illness caused by a highly contagious coronavirus that broke out in Hong Kong in 2002. That outbreak was finally contained. This time it will be different? By the time this issue of MUY hits the newsstand, the Mexican outbreak may have turned into a pandemic; perhaps in a mild one, or perhaps in something more worrisome. It can also happen that it shuts down, after leaving thousands of infected and more than 150 dead. But viruses are unpredictable. There is no crystal ball that can assure us how they will spread and mutate. Theswine fluit is a common disease in pigs. A document from the CDC indicates thatbetween 30% and 50% of the American pig herd is fat. ? Animals are infected throughout the year ?, explains Amelia Nieto, researcher at the National Center for Biotechnology of the CSIC, in Madrid. We look so genetically like pigs? Excuse me? that we have no problem exchanging pathogens with them. According to Juan Ortín, researcher at the center, “it is common for swine flu viruses to infect human beings, and vice versa.”

Almost anything can happen in this game. For example, on May 3 the Canadian Food Inspection Agency (CFIA) reported that a farmer carrying the virus had infected several pigs in Alberta, Canada. The strain responsible for the victims in Mexico, which belongs to the H1N1 subtype, contains the H1 component. This is found in both human and swine influenza viruses. ? What is not normal is that, once they have made the leap from pig to man, viruses are transmitted between us, as has happened now ,? says Ortín.

The unknowns persist. ? We do not know why the virus causes so many deaths in Mexico and not in other countries ,? says Nieto. ? There can be two explanations. One is related to Mexican sanitary conditions: the absence of antivirals to administer in cases of severe infection and the immunological conditions of the population ?, suggests this expert. The other possibility is, according to her, that “the swine virus that circulates there is further away from the human virus of last year.” In other words, the conventional strains that attacked Mexicans in 2008 are less similar to the swine virus than those of the influenza that was installed last winter in the US? Mexicans may have a worse immune memory than Americans.

“This is strange because normally circulating human viruses are very similar,” he continues. The drip of deaths in May in the United States responds to what experts expect, which is a relatively low number of deaths in the world. Obviously, this will depend on the virulence of the new pathogen.The infectious focus of Mexico brings inevitable memories of the Spanish flu of 1918. The qualification of Spanish is unfair, since it did not arise in our country, but in a military garrison at Fort Riley (Kansas, USA). What happened at that time is that the press in Spain – a neutral country in the First World War – did not hide the ravages of the disease; instead, the media of the countries participating in the warfare suffered censorship and they could not report the deaths so as not to discourage the troops.

The1918 pandemicwas? the most devastating we have ever suffered in our history ?, he told the newspaperThe New York TimesJohn R. La Montagne, head of the department of infectious diseases at the US National Institute of Allergic and Infectious Diseases The estimated number of victims ranges, according to sources, between 20 and 40 million. In any case, the mortality figures are similar to those reached by the bubonic plague? The so-called Black Death? between 1347 and 1351, it was able to infect about 2 billion people. This would explain the high number of victims it left, despite the fact that the mortality of the virus was 2.5%, that is, it killed 2.5 out of every hundred infected. During the past century there were two more pandemics: in 1957, the Asian fever, which killed about 70,000 Americans, and 11 years later, the Hong Kong fever, with about 28,000 victims. The flu is a virus whose genetic material is made of RNA. To multiply, you need to strain it? Along with a packet of enzymes? in a cell and hijack its machinery to make the RNA copies that will integrate the new viruses or virions. Thus, if a pig is infected by the human virus and the porcine virus at the same time, the result can be a virion with an RNA that contains fragments of both species. These hybrids cooked in the animal can jump back to the man. Today, the variants that circulate in humans are of the type H1N1, H1N3 and H3N2. Researchers are elucidating the exact genetic makeup of the newvirus ?kindH1N1? responsible for the outbreak.

If we look back, the forecasts are not encouraging. In a magazine reportThe LancetPublished in 2006, the team of specialist Christopher Murray analyzed the 1918 flu data and predicted that the next pandemic would kill some 62 million people, of which 96% would be located in third world countries. Inhabitants of developing countries and refugee populations? It is estimated that in the world there are 50 million people displaced from their homes by armed conflicts, of which half are children? they are the ones who would suffer the worst consequences; in short, those who live on the poverty line. It is sad news that reminds us that tropical diseases, fevers and parasites kill millions of them each year without meriting a newspaper column.

Can a flu pandemic be stopped cold with current media? On April 26, the WHO raised thealert levelfrom thegrade 3little or very little person-to-person transmission of the virus to the4? easy transmission between humans ?, to end up rising in just three days to thegrade 5? imminent pandemic ?. Stopping an illness that has the same symptoms as the conventional flu is a less than impossible task in today’s world. For example, several New Zealand tourists were unknowingly infected in Mexico and within hours returned to their country, at the other end of the globe.

The virus, as of this writing, has appeared in isolated cases in New Zealand, Spain, Scotland, Germany, the United Kingdom, the United States, Canada, and several countries in South America. Travel quietly by plane. In Victorian times, before man flew fast, another rooster would have crowed. ? In the global village, viral transmissions cannot be stopped and, from the outset, the only possible tool is antiviral drugs ,? indicates Nieto. And he adds:? These are used as a shock tool, together with the isolation of detected cases, which are only those with the most obvious symptoms. Can you have a subclinical and asymptomatic infection but still be infected and spread it to other people?

ThesymptomThe usual symptoms of swine flu do not differ from those of seasonal human influenza. ? Until it has killed, we have not known that there was a circulating swine virus ,? says Nieto. The positive thing about this, he explains, is that, as this disease is so similar to the common flu, those who have suffered from the latter? Can be partially protected; Also, conventional vaccines could perhaps provide some immunity? The negative part of the similarity of both pathogens is that the pig can easily circulate between humans.

Virologist Luis Enjuanes, who is Spain’s leading expert on the SARS virus, suggests a comparison between the two crises. That coronavirus infected about 8,000 people, especially South Asia, and 10% of those affected died. With bird flu, transmitted by the H5N1 virus from birds to humans, 421 people were infected, of which 257 died; that is, 59%. This percentage is not very reassuring. With what we know so far, the mortality of swine influenza could be ten times less than that of avian, although the final figure will only be known when we have statistical data.

We have to wait. The epidemiological alert network for influenza, coordinated by the WHO, is vigilant in the face of the evolution of the crisis. We face the summer, with more hours of abundant light, high temperatures and higher doses of ultraviolet light, which deactivate these viruses. If the strain had spread in winter, the circumstances would have been totally different. In the summer season, as Enjuanes indicates, the premises are ventilated more frequently due to the heat, and the burden of the virus in the air is noticeably diluted. This makes contagion more difficult. In winter, on the contrary, the premises are closed, people spend more time in stale environments and the possibility of contracting the virus is much higher.

There’s other good news, Enjuanes says. The first is that virus identification can be done in a matter of hours, so diagnosis is quick. The second, that we have a cure with antiviral drugs such as Tamiflu. Most countries have accumulated large stocks of this drug for fear that a much more deadly virus such as the aviary will spread. In this case, prudence will help us a lot.

Luis Miguel Ariza