Читать книгу Viruses: More Friends Than Foes (Revised Edition) - Karin Moelling - Страница 35

One of the biggest success stories in medicine was the elimination of poxviruses. Poxvirus outbreaks should not be possible any longer, since humans have learnt how to vaccinate against the virus: cowpox prevents smallpox — that was the discovery of Edward Jenner, who first tested this vaccine with his son in 1796 and saved more lives than anybody else in the world has done. Jenner discovered the principle about how to generate a vaccine — use of a related virus causing a mild disease in humans, which protects against the dangerous virus. A cowpox instead of a smallpox virus is such an “attenuated” successful vaccine. The virus is considered extinct. Surprisingly there are occasionally still some pox outbreaks — viruses never disappear completely.

There are only a few laboratories left, in the USA and in Russia, where smallpox viruses are kept under safe conditions. How safe are they against abuse by a bioterrorist attack? This possibility seemed to become real after the anthrax bioterrorism in the USA in 2001, which caused some deaths and resulted in a hectic search for pox-vaccine leftovers, which had been stored for decades. They had been produced on animal skins and by no means corresponded to any acceptable safety standards, but they were then prepared as vaccine again after fivefold dilution to increase the number of doses! In my diagnostics department in Zurich we quickly developed a pox virus test. The necessary information about the viral sequence was freely available to everybody through the Internet! We even practiced how to react in the case of a pox virus alarm, how to prepare samples for a highly sensitive diagnostics method. The fear was a bioterrorist attack against the participants at the annual World Economic Forum at Davos. We dressed up in special safety coats including masks, which many people have seen in the movie “Outbreak” starring Dustin Hoffman. We practiced with a low pressure chamber, under the strictest safety conditions, which would prevent viruses from escaping to the outside — however, the chamber collapsed owing to someone opening the wrong valve by mistake, leaving us with a pile of wreckage. We were lucky, and never experienced an alarm. The fear was slowly forgotten worldwide!

Twenty years earlier I had witnessed the last pox alarm in Berlin. A patient was kept in a quarantine building with policemen sitting outside on high chairs to keep the exits in view and prevent the patient from escaping. Meanwhile, next door at the Robert Koch Institute, the only experienced technician who still knew how to test for poxviruses was busy opening chicken eggs to inoculate the virus and to incubate it for propagation — the only test available in those days. Pox alarm is shown in the movie “The Virus Empire — Silent Killers”. This very informative movie was produced by experts for teaching purposes, and I always showed it at the end of my virology teaching series at the University in Berlin; the series ended on Sundays — and was still attractive enough for the students to come. In the second part of the movie a fictive poxvirus alarm in Berlin is demonstrated.

Another virus, frightening us to this very day, is the influenza virus, the Spanish Flu, called H1N1. About one hundred years ago during World War I influenza viruses killed at least 20 million and possibly up to a hundred million people. The virus was only recently isolated — in 2005, from soldiers and an Inuit woman buried in the permafrost in the Alaskan tundra — and reactivated in the laboratory. The recovered virus was even able to infect animals. This was technically very demanding and in addition also extremely frightening. Rightly, the public media complained about it. Scientists wanted to know why this particular influenza virus was so deadly, especially for young men. There were only few special virus sequences which may have increased the virus’ affinity for lung cells and increased pathogenicity. (Other changes are in the polymerase or the nucleoprotein or the hemagglutinin, so there is still some controversy about which of the changes are deadly.) Major reasons for the pandemic were the war, hunger, humidity, cold temperatures, wounds, lack of hygiene, overcrowded shelters and field hospitals — all factors that cannot be deduced from the viral sequence, of course. All these factors contributed to the catastrophe. We also have to blame ourselves for it.

In 2009 the swine flu started in Mexico, caused also by influenza A H1N1 but distinct from the Spanish Flu. The World Health Organization (WHO) graded the outbreak as worldwide risk and declared it as an epidemic. This was due to a miscalculation. The ratio of people who died relative to the hypothetically infected people was wrong, because nobody knew the real infection rate in a country such as Mexico, where people do not go to see a doctor just with fever. The death rate was 5%, and not 50%, of infected people, no more than in a normal seasonal epidemic, so the alarm was a false one. However, this was a real pandemic because of the high number of countries affected. Safety measures had already been taken quickly and a vaccine production initiated, but it came too late for the Western world; the wave of infections was already flattening off. People in the Southern Hemisphere did not even want the vaccine free of charge. Nobody there took the swine flu seriously. I got infected in China, possibly in an internet café in Shanghai. I was rather sick back home and cancelled my flight from Berlin to Zurich out of fear that I could infect someone and thereby make newspaper headlines as a professor of virology who spreads the virus. I indeed had the swine flu, as verified by my own diagnostics department.

The influenza viruses responsible for the bird flu only became dangerous through manipulation in the laboratory by scientists. Researchers produced from a bird-only virus to a virus infectious for humans. The necessary mutations were even introduced into the viral sequence twice, in two independent laboratories in the USA and Holland. Why do scientists perform such risky experiments? This question was only raised when the scientists were naïve enough to publish their studies. Only then did the research funding organizations begin to ring the alarm bells. A mandatory break, a moratorium for 6 months, was imposed on the studies and their publication. This lasted longer than ordained, and the ban on publication was then softened: details had to be omitted, so that not everybody could repeat the experiment and convert a relatively harmless virus into a dangerous one.

A moratorium with self-restrictions had happened once before, with limitations on the use of recombinant DNA technologies — the construction of new genes by combinations of gene fragments — at the Asilomar conference in 1975, as well as restrictions on gene therapy of human diseases using viruses against cancer. Even today, viruses are still not allowed to replicate when applied for therapeutic purposes in order to prevent the possibility that replicating viruses might infect the germ cells of a patient, which in turn would open up the possibility that the virus could then be transmitted to the next generation. This restriction is strictly fulfilled and accepted. As a consequence, gene therapy is safe — but it is also ineffective for exactly the same reason. It would be much more effective if virus replication were allowed. Other approaches are being pursued now.

The prohibition of the influenza viruses studies can be summarized: “no dual use”, which means, that publications are not allowed to serve two potential purposes, scientific ones and also bioterrorist interests or other abuses. The results on the manipulated influenza viruses were published by omitting technical details, and they were not unimportant, because they showed that four mutations out of 13,500 nucleotides were sufficient for the virus to become “humanized”, to be transmitted from people to people. This is always the main threat. Surprisingly, certain influenza strains already carry three of the four mutations — so we are only one mutation away from a dangerous virus in the wild. The danger is real, and therefore a worldwide surveillance system has been installed, the Sentinella survey of local influenza outbreaks. From this study the annual influenza strains are predicted as a basis for vaccine production for the coming winter. Vaccines are still often produced in chicken eggs, one egg per dose, which requires billions of “special pathogen-free” (SPF) eggs. There are essentially only two drugs against influenza, very few compared with HIV: Tamiflu and Relenza. Tamiflu became a blockbuster and was sold to panicking governments around the world. It is now stockpiled in many storerooms and waiting to be aliquoted when needed. There is a rather strange law according to which only the day of aliquoting is the basis for calculating the expiry date of the drug. In Scandinavia resistant viruses have already shown up, and in Japan Tamiflu seems to lead to increased suicide rates among young people. Influenza should not be underestimated. I caught it, not just a cold by some rhinovirus, and was so ill and semi-conscious that I did not even remember that I had Tamiflu in my refrigerator for exactly this possibility. It is only effective if taken early after infection, for simple reasons, because then the virus load is still small. By the way, paper handkerchiefs should not be thrown into a paper basket next to a desk, but into a bin with a lid, and even an irreplaceable secretary should stay home instead of spreading the virus at work.

There is a broad virus-monitoring system, the Global Viral forecasting initiative (globalviral.org). Google also participates in forecasting, in a surprising way: it is assumed that users of the Internet google “influenza” more frequently if it is spreading, “Google Flu Trends” has predicted the arrival of waves of influenza reliably for more than 100 cities in the US, weeks in advance. Very clever!

Ebola viruses had theoretically for a long time been considered a potential danger. However, in 24 outbreaks during 1976 and 2013 it never became epidemic, with about 1500 fatal cases in total. The outbreaks stayed local and small in West Africa. Yet they were frightening enough for people to flee; this sometimes even included health-care workers, who are at greatest risk because almost every second patient dies of hemorrhages, internal bleedings. People were thought to get so terribly sick, that spreading would be impossible. That changed in 2015. Mobility had increased and markets, schools and other crowds contributed more than before. The epidemic spread through three countries — Guinea, Sierra Leone, and Liberia — with 11,000 deaths reported out of almost 30,000 cases. There is a lack of hospitals, and the families are used to care for the patients, thus exposing themselves to the disease. The funeral traditions, with highly infectious corpses and body fluids were always blamed as a major source of contamination, but this may have changed in the meantime by educating people. There is no therapy except supply of fluid by infusions, which however requires sterile needles. During quarantine, which may last up to 30 days for the infection to manifest itself, people were afraid of attracting the disease there. Those who recover are resistant and could help the others. Even their blood was tested for the presence of potentially protective antibodies. Vaccines are now under investigation that were available in research institutions but too expensive to develop — except under new pressure. The virus is spread by bats and bushmeat, whereby the carriers do not have the disease. Carrier animals comprise also dogs, pigs and perhaps rodents, which can be found at many locations worldwide and may be infectious. Endogenization of Ebola sequences has been shown to be a characteristic property of healthy carriers and potential transmitters. Endogenization means the presence of viral sequences in the genome of the animals (see below).

Unexpected was the observation that Ebola viruses can hide in reservoirs like the human brain and caused severe encephalitis several months after recovery of a patient. This was observed for the first time with a nurse who was thought to have survived Ebola but came down 6 months later with viruses in her brain. Viruses can also last for four months in semen of men who have recovered. The newly developed vaccine may become important in the future.

Germany has a certain tradition with Ebola, since it is a close relative of the Marburg disease virus. The Behring company — close to Marburg, Germany — experienced some transmissions of the virus to animal keepers by imported apes in the 1960s. About 30 people became infected and one-third of them died. Then, 40 years later, the television host Gunther Jauch invited survivors and scientific specialists to take part in a talk show. First of all we had to learn to applaud loudly, and long enough, when the host entered the scene. Then there is always the discussion about bioterror-ism with this virus; however, since nobody has a protection or cure yet, this would be dangerous for the terrorists themselves and not attractive for bioterrorism. Based on the tradition of Marburg there is now a safety laboratory at the highest Biosafety Level (BSL4) for Marburg and Giessen Universities. Also, the Robert Koch Institute in Berlin opened a new high-containment laboratory in 2015. There are only about half a dozen such laboratories in the whole of Europe. So Germany has a big chance to contribute to knowledge about newly emerging dangerous pathogens and diseases. It is known that viruses rarely disappear completely, therefore we may have to be aware of viral “come-backs”.

SARS (severe acute respiratory syndrome) is a disease which also requires laboratories working at the highest safety level. In Hong Kong the coronavirus, which causes SARS, has escaped more than once from a research institute. Most surprising was the press release in 2014 that thirty containers with SARS samples had disappeared from the liquid nitrogen tank, the storage place for the samples in the safety laboratory in Paris. They were not declared as such for safety reasons, so that nobody would know about the dangerous contents. I guess what happened is that someone simply needed space in the tank and cleaned it up. Tanks are notorious for always being full and often ancient samples reappear, years after they have been put there. Sometimes this opens up new research fields, as in the case of a retrovirus with a then new oncogene Jun. Even in the refrigerator of the seminar room which I once cleaned up by myself, I discovered a pot of margarine which had survived there unnoticed for seven years in spite of daily use of the place. Probably the samples from Paris ended up safely in the steam sterilizer according to the rules — but were lost for research purposes. Even in my safety laboratories in Zurich we discovered a hole in the wall — which was not really dangerous because of low pressure in the room and sterile cabinets — but still, what an embarrassing surprise.

One late night a nurse came to my office in Zurich, her arms full of sample tubes. A pilot from the Philippines, potentially sick with SARS, was stationed in the hospital. This rang an alarm bell. First I called a colleague at the Institute of Tropical Medicine in Hamburg for advice. I had to wait, until he returned around midnight from a TV show on SARS. He then dictated a list of reagents, some of which had just that week become available in Berlin, primers for a sensitive laboratory test (a polymerase chain reaction, PCR, which I shall explain below). I thought that that would simply take too long for a high-risk patient. I suggested flying to Hamburg with the samples and analyzing them there. The transport was made possible, even without my accompanying the samples, by World Courier. About ten containers had to be packed around each other like a Russian doll. The bicycle courier for the airport was already waiting, when one container was left. I stealthily let it disappear in the pocket of my lab-coat, so as not to cause any further delay. At night the Institute from Hamburg gave the green light and informed me that the result was negative, which was also a big relief for the health-care workers at the hospital. A SARS patient arrived in Frankfurt, in Germany, and was successfully quarantined and treated — and recovered without causing a local outbreak as in Canada or Singapore. There paramilitary actions — such as daily reports of the body temperature of employees — were taken successfully. The World Health Organization was very alert and helpful in managing the dangerous outbreaks all over the world by issuing frequent reports and daily advice. Again, bats were the reservoirs of the virus, as in the case of Ebola. Bats live in colonies at high population densities and transmit viruses without becoming sick themselves — like resistant survivors — those that did become ill succumbed. Some people say that bats may have different immune systems, especially a much higher interferon level, therefore getting sick more rarely. In the meantime, therapies against SARS have been developed: inhibitors of its protease. A similar approach was also successful against HIV. Meanwhile in the United Arab Emirates, a new SARS outbreak has occurred, killing a sheik and his son and, later, others. It is most probably transmitted by camels. The virus was isolated at the Erasmus Medical Centre in Rotterdam. The location of isolation is normally used to coin the name of an isolate, so in this case it was first called EMC-virus, but is now known as Middle East respiratory syndrome, MERS-coronavirus. Infection rates are increasing. A short episode was experienced in Korea in 2015 in a hospital — and was spread through family members, because they take care of patients, while nurses as such do not exist. The virus was rapidly brought under control. Please note SARS was controlled by very old-fashioned hygiene measurements and paramilitary actions, not by a fancy vaccine or therapies.

One day my co-worker Alex came into my office: “I am so sick I am dying.” I remembered pictures of measles from virology textbooks (I am not a physician) and diagnosed measles. Alex had just come back from the Ukraine, from his grandmother’s birthday, where the Internet indicated a measles outbreak. Political uncertainties had prevented vaccination of a whole generation of people. Everybody in the Institute in Zurich was tested for measles antibodies and was vaccinated immediately if necessary; that is not too late. Alex did not go to the hospital as he was told to, but took the tram and infected a child. Fortunately, both of them recovered. Even a doctor for children recently infected the children in his practice office with measles because he had never been vaccinated. This raised a debate about mandatory vaccination of such a profession. 1.7 million people die every year of measles. Many parents decline the vaccination out of fear of side effects (autism was claimed to be such a side effect, but falsely). Measles is especially dangerous for adults, with encephalitis as a potential complication. Measles has written history, and depopulated islands; it contributed to the decline of the Mayas, influenced the outcome of the battles of Charlemagne, and accelerated the end of the Roman Empire. Measles can also affect animals. Some people may remember the extinction of numerous seals in the North Sea.

The fear of measles vaccination teaches us a lesson — vaccination is based on trust and education and correct information. The interest in vaccination plummeted when the information spread that the American Secret service ran a fake vaccination campaign by taking blood samples in a rural area of Pakistan to uncover the hiding place of Osama bin Laden. This increased refusal rates for vaccines for years.

Noroviruses are not very dangerous, but they are extremely contagious. A few virus particles are sufficient to cause an infection. The television cruise ship “Deutschland” was the first ship to be hit by noroviruses in the 1990s. It is based in Neustadt, on the Baltic, the city of my childhood. The newspapers speculated about the cause, the yellow and black quarantine flag was raised and nobody was allowed to leave or enter the ship. The head of my diagnostics department in Zurich, whom I called, immediately gave the correct answer: noroviruses. They were contaminating the drinking water that had been taken on board. This is a threat since then it could happen on any cruise ship and perhaps cause deaths among the elderly or weak passengers. Every crew now has to learn how to cope with this — isolate the infected passengers completely! A hospital close to Zurich had to be locked for several days. And a city nightline train was isolated at night in Frankfurt because of infected school kids. I should probably avoid the six-bunk couchette cabins in this train in future, though in fact I am still using them.

And what about ticks? If the doctor does not know what to say, he may have to be informed whether you were bitten by a tick. You should save the bug, if you can, for diagnostic purposes. It may have transmitted bacteria, Borrelia burgdorferi, causing Lyme disease — or a virus, the “tick-borne encephalitis” virus (TBEV). The bacteria can be treated by antibiotics, but TBEV cannot be treated at all. This can be diagnosed with the bugs. A bite is sometimes but not always noticeable by a moving red halo on the skin. At Princeton everybody knew and talked about this risk. One day, the famous John Hopfield — known for the Hopfield artificial neural network — pretended to look crazy and pointed out that the deer in his garden very often have ticks and could make him look like that. He took antibiotics just to be on the safe side after a bite. One needs to remember this if one cannot explain the cause of a serious headache. By the way: for a summer holiday in Austria, vaccination against ticks is mandatory and has to be done well in advance. Their chief virologist is a tick specialist — he must know!

New viruses are often not new, but they are easier to diagnose or show up at unexpected locations. One day the crows fell down from the sky over New York City. Within only a few years a new virus had conquered the whole of the USA, the West Nile virus (WNV). As indicated by its name, it came not from New York but probably by airplane from Israel. Mosquitoes get infected by birds and can induce encephalitis in humans. Air travel is the fastest way for viruses to spread. Within 24 hours viruses can get around the world in an airplane, often lurking in the air-conditioning system.

The public used to complain if health authorities do not take precautions or actions fast enough. We all have to learn that there are newly emerging viruses, which take us by surprise. The Zika virus is one of them I had never heard of it until early in 2016. It was for decades a local virus of monkeys in Uganda, the “Zika” forest, and then spread to over 32 countries in 2016, so that the WHO announced a “global health emergency”. The virus may cause a microcephalus in newborns in Brasilia, and brain infections and may be sexually transmitted. Again the poorest are hit the hardest. Two types of mosquitos (Aedes aegypti, which also transmits malaria and is called the yellow fever mosquito, and Aedes albopictus, the tiger mosquito) can transmit the virus, which is similar to dengue fever virus and yellow fever virus. The mosquitos need to be eliminated by insecticides or infected with bacteria so that the virus is blocked, or made sterile, so that no new females produce progeny insects — all very difficult to do. The tiger mosquitos have reached south European countries. They can resist cold temperatures and multiply in water puddles. This is a new outbreak — but will not be the last one.