07_Pandemia

Pandemics

Pandemics have been known from the very early times of recorded human history, affecting human populations on a large scale, wiping out civilizations, directing outcomes of wars and shaping human cultural, social, economic and political life. Black Death or plague, smallpox, malaria and cholera are among well-known infectious diseases that caused most persistent epidemics until the introduction of effective preventive measures or the discovery of successful medicine. For example, Black Death, a bacterial disease that causes death in a few days, with gangrenous skin and flesh, which turns black, is transmitted by rodents’ flies, and from man to man. Plague killed half of the European population between the 14th and 17th centuries and also had devastating effects in other parts of the world. It was brought to Europe In the 14th century by Genoese merchant ships departing from the Black Sea and it spread first to Sicily, Genoa and Venice and then to other parts of Europe. Venice experienced many outbreaks of plague in the next 300 years despite the fact that the city authorities were the first in the world to establish strict preventive measures to mitigate the outbreak of plague, such as better hygiene by removing corpses from the streets, isolation of infected people on islands, with newly built lazarettos, 40 days quarantine (“quaranti”) for those suspected of infection and foreigners. They also kept records of deceased people, of outgoing and incoming persons and introduced strict rules in everyday life.

Pandemia
When the plague had more or less died out, smallpox became the most terrible messenger of death from the 17th century on. Smallpox is a highly contagious virus disease with a mortality rate of 20-30% and is transmitted through inhalation of airborne smallpox virus. The disease usually lasts for 16-20 days and at the end, the infection is manifested in those that survive by skin covered with characteristic scabs and scars, and frequently by blindness. Vaccination, by using smallpox and later cowpox scabs, had been discovered to be a very effective treatment against smallpox infection as early as the 10th century in China and was later adapted by Europeans, practiced mainly in royal courts and in a significant number of soldiers of winning armies. Smallpox was additionally spread by Spanish and other conquistadors to America, where the disease had a fatal effect on the non-immune native American populations.

The Spanish flu is an example of the disaster of not treating a virus. Caused by the deadly influenza virus, no honest information was given to the people by countries’ authorities and no vaccines were developed. Newspapers reported the epidemic’s effects only in neutral Spain and this gave rise to the name “Spanish” flu. The flu was brought to Europe by American soldiers at the end of the 1st World War and killed between 17 million and 50 million people, possibly more since there are no reliable epidemiological data.

What are these infectious agents? The majority of them are small living organisms or other structures, invisible to the naked eye, called bacteria and viruses, which were discovered at the end of 19th and beginning of the 20th century. Bacteria are single cell organisms capable of living on their own, since they possess all the necessary cellular machinery for reproduction and multiplication by living in various feeding grounds (living organisms, surfaces, hot springs etc. They also have an interesting social life, communicating and combining for more successful survival. The bacteria that we know are classified as beneficial (fruit fermentation, probiotics, gut bacterium etc.), harmful, disease-causing bacteria (plague, syphilis, cholera, tuberculosis, food poisoning etc.) and those with which we happily cohabit. Luckily, science has provided antibiotics as effective drugs against harmful bacteria and these have been combined with preventive practices in treatment since the 2nd World War. However, viruses are sub-cellular structures of molecules which cannot live on their own, they can multiply (sole purpose of their being) only in hosts (bacterium, fungus, plants, animals, humans), from which they borrow reproductive cellular machinery. They cause harm to a host by multiplication and finally damaging the host cells. The most effective measure for combatting human virus diseases is vaccination, using impaired viruses to trigger the immune system and to hopefully build long-term immunity.  Preventive measures to avoid infection are of course the best bet!

We are now faced with a Covid-19 pandemic, a virus disease that has spread throughout the world. As of October 20th, 39.6 million people have tested positive for the infection and 1.1 million people have died from Covid-19. The numbers for individual countries, of course, vary depending on the number of tests, the quality of the healthcare system and treatment possibilities, time from initial outbreak and population characteristics such as age, sex and overall health. It is similar with modelling disease development because, as with any model and forecast, the results heavily depend on the quality of input data and the applied algorithm. However, a group of Slovene data-informed volunteers have developed an interesting website, https://covid-19.sledilnik.org/sl, which presents the current situation on Covid-19 in Slovenia fairly realistically.

Covid-19, a novel severe acute respiratory syndrome (SARS) coronavirus, was first isolated in December 2019 in Wuhan, China, where 3 people with unusual pneumonia were treated in hospital. Covid-19 is related to six other known coronaviruses that infect humans. Two of them, SARS and MERS, have caused outbreaks. The reservoir of coronaviruses is probably bats, which have an atypical immune system and can tolerate all these viruses. Coronaviruses are usually transmitted to humans through an intermediate animal, as in the case of MERS (Middle East Respiratory Syndrome) through camels and, in the case of Covid-19, probably through pangolins, a mammal, as we are, covered with scales. It is highly prized for its scales in Chinese traditional medicine, mainly as an aphrodisiac and its meat is considered a speciality.  It is hunted in the wild in Asia, raised on illegal farms, since it is a protected species, and sold in fresh meat markets, from where Covid-19 probably emerged in Wuhan. It has spread from there all over the world through mass travel, migrations, business encounters and neglect of preventive measures.

Covid-19 enters the human body through the nose, mouth or eyes, which is why all the preventive measures against infection with Covid-19 are so highly emphasized by our epidemiological authorities. It then attaches to host cells in the airway with protruding spikes from the virus (remember the many pictures of a crownlike virus) and it enters the cell(s), where it multiplies, infects neighboring cells and the process goes on. Various outcomes can manifest when the virus is within the body, because our immune system, the guard against foreign agents, is highly diverse. After infection with Covid-19, some will develop mild symptoms such as fever and a dry cough, or no symptoms at all; others, with a weakened immune system, will be more severely affected, including pneumonia, acute respiratory distress syndrome, sepsis, septic shock and many other complications. It is already well established that older people form a high Covid-19 risk group, probably because the immune system is no longer as powerful with age as with young people.

The present Covid-19 pandemic is just one of the pandemics that have struck the human race over the course of history. We are better equipped today with knowledge, information and other means of combatting a virus disease outbreak than ever before in the past, although the epidemiolocal picture is not very encouraging. Until successful and safe medication is developed, on which many research laboratories throughout the world are working, we must rely on protective measures.

Stay safe, wear a mask, wash your hands with soap and keep physical distance! And let’s hope that we can make a better post-coronavirus world than the previous one.

Pandemije

Pandemije so bile znane že v zgodnjih časih naše zgodovine, prizadele so človeško prebivalstvo v velikem obsegu, uničevale civilizacije, usmerjale izide vojn in oblikovale človeško kulturno, socialno, gospodarsko in politično življenje. Črna smrt ali kuga, črne koze, malarija in kolera so med znanimi nalezljivimi boleznimi, ki so do uvedbe učinkovitih preventivnih ukrepov ali odkritja uspešnih zdravil povzročile dolgotrajne epidemije. Na primer, črna smrt, bakterijska bolezen, ki v nekaj dneh povzroči smrt z gangrensko kožo in tkivom, ki postane črno, prenašajo uši glodavcev in s stiki med ljudmi. Kuga je med 14. in 17. stoletjem ubila polovico evropskega prebivalstva, uničevalne učinke pa je imela tudi v drugih delih sveta. V Evropo so jo v 14. stoletju prinesle genovske trgovske ladje, ki so odhajale iz Črnega morja, najprej pa se je razširila po Siciliji, v Genovi in Benetkah, nato pa še v drugih predelih Evrope. Benetke so v naslednjih 300 letih doživele številne izbruhe kuge, kljub temu da so mestne oblasti kot prve v Evropi uvedle stroge preventivne ukrepe za ublažitev razsajanja bolezni kot na primer boljšo higieno z odstranjevanjem trupel iz ulic, izolacijo okuženih ljudje na otokih z novo zgrajenimi lazareti, 40-dnevno karanteno (“quaranti”) za osumljene na okužbo in tujce. Vodili so tudi evidence preminulih ljudi, odhajajočih in prihajajočih osebe v mesto ter uvedli stroga pravila v vsakdanje življenje.

Pandemia

Ko je kuga bolj ali manj zamrla, so od 17. stoletja dalje postale črne koze razširjen glasnik smrti.  Črne koze so zelo nalezljiva virusna bolezen s smrtnostjo 20–30% in se prenašajo z vdihavanjem virusa črnih koz v zraku. Bolezen običajno traja 16–20 dni in na koncu se okužba pokaže pri tistih, ki preživijo, s kožo, prekrito z značilnimi krastami in brazgotinami, pogosto pa tudi s slepoto. Že v 10. stoletju so na Kitajskem uvedli cepljenje z uporabo posušenih kozjih krast  kot zelo učinkovito sredstvo proti okužbam s črnimi kozami. Evropejci so ta princip cepljenja pozneje prevzeli, izvajali pa so ga predvsem na kraljevih dvorih in pri številnih vojakih zmagovalnih vojsk. Španski in drugi konkvistadorji so črne koze razširili v Ameriko, kjer je bolezen imela usodne posledice za indijansko populacijo.

Španska gripa, ki so jo v Evropo prinesli ameriški vojaki proti koncu 1. svetovne vojne in je razsajala dve leti, je primer slabo obravnavane kužne bolezni. Smrtonosni virus gripe se je zelo hitro širil med prebivalstvom izmučenim od vojne, vendar pristojni organi v večini držav ljudem niso dali poštenih informacij, niso uvajali preventivnih ukrepov in niso razvili nobenih cepiv. Le v nevtralni Španiji so časopisi poročali o učinkih epidemije, kar je dalo tej gripi ime “španska”. Za posledicami  te epidemije je umrlo od 17 do 50 milijonov ljudi, verjetno tudi več, ker ni zanesljivih epidemioloških podatkov.

Kdo so povzročitelji kužnih bolezni? Večina jih je majhnih organizmov ali drugih struktur, nevidnih s prostim očesom, ki jih imenujemo bakterije in virusi in so bili odkriti konec 19. in v začetku 20. stoletja. Bakterije so enocelični organizmi, ki lahko živijo samostojno, ker imajo vse potrebne celične mehanizme za  razmnoževanje. Njihov habitat je zelo pester saj lahko živijo v drugih živih organizmih, vključno s človekom, na različnih površinah, celo v izvirih vroče vode in podobno, od koder črpajo hranila za svoj razvoj. Imajo tudi zanimivo družabno življenje, medsebojno namreč komunicirajo in se povezujejo v skupine z namenom uspešnega preživetje. Bakterije, ki jih poznamo, opredeljujemo kot koristne bakterije (fermentacija sadja, probiotiki, črevesna mikroflora itd.), škodljive bakterije, ki povzročajo bolezni (kuga, sifilis, kolera, tuberkuloza, zastrupitev s hrano itd.) ter na tiste s katerimi srečno sobivamo. Na srečo je znanost odkrila antibiotike kot učinkovita zdravila proti škodljivim bakterijam, ki so v medicinski praksi že od 2. svetovne vojne naprej, seveda v kombinaciji s preventivnimi ukrepi.

Po drugi strani so virusi strukture molekul, ki ne morejo živeti samostojno in se lahko se množijo samo s pomočjo gostitelja (bakterijah, glivah, rastlinah, živalih, ljudeh), pri katerih si sposodijo reproduktivne celične mehanizme. Gostitelju škodujejo z razmnoževanjem in dokončnim poškodovanjem gostiteljskih celic. Najučinkovitejši ukrep za boj proti virusnim boleznim človeka je cepljenje z uporabo oslabljenih virusov, ki sprožijo imunski sistem za tvorbo virusno specifičnih protiteles in se tako ustvari kratkoročna, še bolje pa, dolgoročna imunost. Preventivni ukrepi za preprečevanje virusnih okužb so seveda najboljša izbira!

Zdaj se soočamo s pandemijo Covid-19, virusno boleznijo, ki se je razširila po vsem svetu. 20. oktobra letos  je bilo 39,6 milijona ljudi pozitivnih na okužbo in 1,1 milijona ljudi je umrlo zaradi Covid-19. Številke za posamezne države se seveda razlikujejo glede na število opravljenih testov, kakovost zdravstvenega sistema in možnosti zdravljenja, časa od začetka izbruha epidemije in značilnosti populacije, kot so starost, spol in splošno zdravstveno stanje. Podobno je z modeliranjem razvoja bolezni, ker so kot pri vseh modelih in napovedih rezultati močno odvisni od kakovosti vhodnih podatkov in uporabljenega algoritma za njihovo obdelavo. Ob tem velja omeniti skupino slovenskih podatkovnih strokovnjakov, ki so prostovoljno razvili zanimivo spletno stran https://covid-19.sledilnik.org/sl, ki dokaj realno predstavlja trenutno stanje in napovedi o Covid-19 v Sloveniji.

Covid-19, nov hud akutni respiratorni sindrom (SARS), je bil prvič izoliran decembra 2019 v Wuhanu na Kitajskem, kjer so v bolnišnici zdravili 3 osebe z nenavadno pljučnico. Covid-19 je eden izmed šestih znanih koronavirusov, ki okužijo ljudi. Dva izmed njih, SARS in MERS, sta že povzročila izbruhe epidemije. Rezervoar koronavirusov so verjetno netopirji, ki imajo netipičen imunski sistem in lahko tako prenašajo vse te viruse. Koronavirusi se iz netopirja na človeka običajno prenašajo prek vmesne živali, tako kot pri MERS (bližnjevzhodni respiratorni sindrom) preko kamel in v primeru Covid-19 verjetno preko luskavcev, sesalcev pokritimi z luskami. Zaradi lusk je ta žival zelo cenjena v kitajski tradicionalni medicini, predvsem kot afrodiziak, njegovo meso pa velja za specialiteto. V Aziji luskavca lovijo v divjini, gojijo ga na ilegalnih kmetijah, saj je zaščitena vrsta, prodajajo pa ga na tržnicah svežega mesa. Covid-19 verjetno izvira iz takšne tržnice v Wuhanu, od koder se je razširil po vsem svetu z množičnimi potovanji, migracijami, poslovnimi in drugimi srečanji in zanemarjanjem preventivnih ukrepov.

Covid-19 vstopi v človeško telo skozi nos, usta ali oči, zato naši epidemiološki organi tako zelo poudarjajo znane preventivne ukrepe proti okužbi. Nato se pritrdi na gostiteljske celice v dihalnih poteh s štrlečimi beljakovinami na zunanjem ovoju virusa (spomnite se številnih slik kornavirusa) in nato vstopi v celice, ugrabi celične mehanizme za svoje razmnoževanje, nato okuži sosednje celice in se širi po tkivu. Ko je virus v telesu, se lahko pokažejo različni bolezenski znaki, ker je naš imunski sistem, ki nas varuje pred tujki, zelo raznolik. Po okužbi s Covid-19 se bodo pri nekaterih pojavili blagi simptomi, kot sta zvišana telesna temperatura in suh kašelj, ali pa se simptomi sploh ne pojavijo; drugi, z oslabljenim imunskim sistemom, bodo huje prizadeti, vključno s pljučnico, sindromom akutnega dihalnega strese, sepso, septičnim šokom in številnimi drugimi zapleti. Poznano je, da starejši ljudje tvorijo visoko rizično skupino za Covid-19, ker imunski sistem s starostjo ni več tako vitalen kot pri mladih.

Pričujoča pandemija Covid-19 je le ena od pandemij, ki so prizadele človeško raso. Danes smo bolje opremljeni z znanjem, informacijami in drugimi sredstvi za boj proti izbruhu virusne bolezni kot kdaj koli prej v preteklosti, čeprav epidemiološka slika ni preveč vzpodbudna. Dokler ne bodo na razpolago uspešna in varna cepiva, ki jih razvijajo številni laboratoriji po vsem svetu, se moramo zanašati na zaščitne ukrepe.

Ostanite varni, nosite masko, umivajte si roke z milom in bodite na fizični razdalji! In upajmo, da bomo lahko post-koronavirusni svet naredili boljšega od predhodnega!