Since March 11, the spread of Covid-19 is officially a pandemic, following the declaration of the World Health Organization (WHO). In reality, that statement only indicated that the virus had already spread to many countries and that most of the world’s population could be infected, but the truth is that the word ‘pandemic’ impresses and sounds alarms of anyone.
The situation is complex and requires measures to be taken in all countries, but it is not the first time that there has been a global threat caused by viruses or bacteria:
The black plague or bubonic plague (1347 – 1351)
■ What caused it: Yersinia pestis bacteria.
■ Contagion and symptoms: In the Middle Ages, contagion was attributed to miasmas (the effluvia that diseased bodies give off, corrupted matter and stagnant water). To protect themselves from them, the doctors used masks filled with aromatic substances, with two small holes next to the nose. The bacteria were actually transmitted through parasites such as fleas and lice that lived on rats, rodents, or humans, and also through exposure to bodily fluids from an infected animal.
It caused coughing up blood on expectoration, shortness of breath, nausea, vomiting, high fever, headache, and weakness. The infected lymph nodes swelled and could break open. The disease had an incubation period of between 16 and 23 days before showing symptoms and between three and five days until death occurred. The plague manifested itself in the groin, armpits, or neck, with swollen glands; These infected lymph nodes were called buboes, hence one of the names by which the disease was known. Another variant was the septicemic plague, in which the contagion passed into the blood causing dark spots on the skin (hence the name black plague).
■ What happened: The epidemic is believed to have started in Asia and reached Europe via trade routes; specifically, on the ship of some Genoese merchants fleeing the epidemic. From there it spread throughout most of Europe, escaping cold regions such as Iceland and Finland.
■ How it was solved: Figures vary widely, with sources saying there were between 50 and 200 million deaths. Some 25 million people died in Europe during the first wave and between 40 and 60 in Africa and Asia. In cities like Paris or Florence half the population died. In Spain the population went from 6 to 2.5 million inhabitants, which represents a loss of between 60 and 65% of the population. It gradually disappeared as hygienic conditions improved.
New black plague (1885-1920)
■ What caused it: Again, the Yersinia pestis bacillus.
■ Contagion and symptoms: the same as in the plague of s. XIV.
■ What happened: From the s. XIV the plague made appearances from time to time, albeit in less virulent waves. The 1885 outbreak began in China, in the Yunnan province, and spread to several countries in Asia and the Caribbean. Although it was considered resolved in 1920, cases continued to occur until 1959.
■ How it was resolved: There were an estimated 12 million deaths. It was much less serious than the plague of the s. XIV since the hygiene of the time was better. It was the last time the plague became a real threat, although cases continue to appear sporadically. During this pandemic, in 1894, the bacillus that caused it was isolated in Hong Kong. In 1905 the role of fleas and rats was discovered.
Spanish flu (1918 – 1920)
■ What caused it: Influenza A virus of the H1N1 subtype.
■ Contagion and symptoms: Through saliva when the patient speaks, coughs or sneezes.
■ What happened: The virus was especially primed among people between the ages of 20 and 40. Despite the name with which it has gone down in history, its origin is not clear, although most researchers believe that it began at the military base of Fort Riley, Kansas (USA). From there he arrived in Europe with the displacement of soldiers to participate in World War I. Due to the conflict, the states exercised censorship over the press, which did not talk about the disease, but Spain was a neutral country and information about the pandemic was published here, hence the name “Spanish flu.”
The symptoms were high fever, earache, tiredness, diarrhea and vomiting, although most of the deaths were due to secondary bacterial infections, especially pneumonia.
One of the latest investigations, published in the ‘Proceedings of the National Academy of Sciences’ established that one of the reasons that this strain of the flu virus was so lethal was because people between 20 and 40 years old probably had not been exposed to the virus during childhood and had no immunity. Another cause points to the fact that the massive transport of troops – included between those ages – during the war favored contagion.
An article written by researchers from the ‘Loyola University Medical Center’ and published in the ‘Journal of The American Society of Cytopathology’ establishes that some of the measures that were adopted then (closing of schools, prohibition of large gatherings or the widespread use of masks ) reduced the virulence of influenza.
■ How it was solved: It is estimated that at least 50 million people died worldwide. In Spain there were 8 million people infected and 300,000 dead. It must be remembered that Alexander Fleming did not discover penicillin until 1928. In 1920 the virus lost its fatality and the outbreak disappeared.
Asian flu (1957 – 1958)
■ What caused it: Influenza A H2N2 virus.
■ Contagion and symptoms: The usual flu, which could cause various pulmonary complications such as bronchopneumonia, myocarditis or pulmonary edema.
■ What happened: It arose in Yunan, China, and spread to Singapore in February 1957. It is believed to have originated from a combination of avian (wild duck) and human strains, mediated by the swine breed . It arrived in Hong Kong in April and was extended to Singapore, Taiwan and Japan in two months, then to the United States, India and Australia. In Spain it infected a third of the inhabitants. The first wave mainly affected children, adolescents and young people and the second affected more adults.
■ How it was solved: The rapid creation of a vaccine and antibiotics to combat secondary infections kept it at bay, although it left around two million deaths (10,000 of them in Spain, where more than four million people sickened). Its lethality was low, but it spread very quickly. It ended up disappearing little by little and has not been included in the flu vaccine since 1968.
The Hong Kong Flu (1968)
■ What caused it: The H3N2 flu virus.
■ Contagion and symptoms: It was a virus similar to the 1918 flu.
■ What happened: It emerged as a subtype of the Asian flu. The outbreak began in Hong Kong in July 1968 and is believed to have reached Europe via English travelers who had been to the Asian region, then a British colony. He came to the United States with the soldiers returning from the Vietnam War.
■ How it was resolved: It was a highly contagious flu. This virus is still active but is already part of the seasonal flu strains. It is estimated that more than a million people died; 3.5 million people were infected in Spain and 8,400 died. In 1969 the vaccine was achieved.
HIV (Since the 1970s)
■ What caused it: The Human Immunodeficiency Virus (HIV) that causes Acquired Immune Deficiency Syndrome (AIDS).
■ Contagion and symptoms: It is transmitted through unprotected vaginal, anal or oral intercourse, or through the bloodstream (by sharing sharp or pointed objects such as needles or syringes). Due to this form of contagion, during the years of greatest expansion of the epidemic, the patients were homosexuals, heroin addicts, hemophiliacs and those who had received a transfusion of infected blood.
Mother-to-child transmission during pregnancy, childbirth or breastfeeding is possible but has now been reduced in the United States and Europe thanks to antiretroviral treatments.
■ What happened: It is believed that its origin is a zoonosis originating from apes that happened to people in Central Africa, but when the situation really broke out was when the epidemic reached the United States. In 1981, the US Center for Disease Control and Prevention (CDC) reported five cases of pneumonia and, the following month, several cases of Kaposi’s sarcoma, a type of skin cancer. The patients were mostly homosexual men who coincided in other diseases that were later discovered to be opportunistic. Later patients appeared who had in common being drug addicts.
During the first years, the sick were socially isolated because people did not know how they were infected. In 1983 scientists from the Pasteur Institute isolated HIV and the American Robert Gallo identified it as the cause of the disease. Patients in the first years of the pandemic did not exceed a year of life many times. Stigmatization was focused on homosexuals, which favored the spread of the disease to other countries through heterosexual patients.
HIV deteriorates the patient’s defense system and that is when the diseases that define AIDS such as pneumonia, tuberculosis, candidisasis, cytomegalovirus, herpes, toxoplasmosis, Kaposi’s sarcoma, MAC (mycobacterium avium) or hepatitis C infections can appear.
■ How it was resolved: Not resolved. If it is not treated with antiretrovirals, it has a mortality of 80%. There are currently, at least, between 25 and 35 million deceased. According to the WHO and UNAIDS, in 2018 there were some 38 million people infected with HIV worldwide, of which 1.7 million are children.
In Spain, according to data from the Ministry of Health, in 2017 there were 3,353 new diagnoses and 0.4% of the population were infected.
At the moment there is no cure but retroviral treatments have managed to greatly reduce its evolution and today it is a chronic disease for many patients. Where it continues to be a highly lethal pandemic is in developing countries, where patients do not have the possibility of accessing medication.
Ebola (Since 1976)
■ What caused it: The Ebola virus, from the filovirus family.
■ Contagion and symptoms: The disease caused by the Ebola virus is also called Ebola hemorrhagic fever. The incubation period ranges from 2 to 21 days, but the person is not contagious until symptoms appear. It begins with a ‘dry phase’ with sudden fever, severe weakness, and sore muscles, headaches, and sore throats. As the disease progresses, the ‘wet phase’ arrives with vomiting, diarrhea, skin rashes, kidney and liver dysfunction and, in some cases, internal and external bleeding.
■ How is it spread?: The WHO states that it is introduced into the human population through close contact with organs, blood, secretions or other bodily fluids of infected animals that have been found dead or sick in the jungle. Fruit bats are known to be hosts. Later, it is transmitted from person to person by direct contact through the mucous membranes and the skin with organs, blood, secretions or other body fluids of infected people such as feces, urine, saliva or semen. Or by indirect contact with materials contaminated by said liquids, as well as by burial ceremonies that involve direct contact with the corpse. It can also be transmitted by men sexually, and it is recommended to test for the virus in the semen of an infected person up to three months after the onset of symptoms. Patients are contagious as long as the virus is present in the blood.
■ What happened: The Ebola virus has existed for 100 years, but when it affected humans it was isolated populations. Between 2014 and 2016, the largest epidemic occurred since the virus was discovered in 1976, with two simultaneous outbreaks in southern Sudan and the Democratic Republic of the Congo, the latter on the banks of the Ebola River. This area is the intersection of three countries with a lot of movement of people, so it spread to Guinea, Sierra Leone and Liberia.
It is a more serious and less contagious disease than that produced by Covid-19. According to the WHO, the lethality in recent outbreaks is approximately 50% and in previous outbreaks they were between 25 and 90%.
■ How it was resolved: Given the ease of contagion, WHO recommends controlling and preventing infection, surveillance and tracking of cases, safe burials, and social mobilization. There is no cure yet and the treatment that is followed is rehydration and symptomatic treatment, which improve survival. Various forms of hemotherapy, immunotherapy and drug therapy are under development, and there is an experimental vaccine.
SARS (2002 – 2003)
■ What caused it: The SARS-CoV coronavirus.
■ Contagion and symptoms: The patients presented fever, cough and pneumonia or respiratory distress syndrome. It is transmitted through droplets produced by coughing or sneezing. The average incubation time was 4 to 6 days, although it could be extended to 13 days. The patient began to spread from the onset of fever, the first symptom – sometimes accompanied by chills-, which was followed by a dry cough, myalgia, headache, general malaise and sore throat and, a little later, pneumonia with respiratory difficulties that might require mechanical ventilation.
■ What happened: It originated in Guandong (China), associated with a live animal market, and went from cats to humans, with the bat as host. One of the factors that influenced it to become a pandemic was the speed of its spread: in 24 hours it had spread to five countries and was the first warning of what could happen in a globalized world. The measures that were adopted to stop it were isolation of the sick, quarantine of those who had been exposed to the virus, individual protection of health workers, biosafety measures in laboratories, precautions for travelers and specific information on the evolution of the epidemic.
■ How it was resolved: It is considered the first pandemic of the s. XXI. There were 774 official deaths and 8,098 infections in 29 countries around the world. Children were the least affected segment of the population. The most affected country was China, with 349 deaths. In Spain there was a case. The WHO explains on its website that the virus spread to 30 countries and areas of the world but only nested in six, hence it was relatively easy to contain. According to the National Center for Genomic Damage of China (NGDC for its acronym in English), Covid-19 is 80% similar to the one that caused the SARS pandemic, although the contagion of the latter was much lower since it was replicated in the lungs.
Flu A, H1N1 flu, or swine flu (2009)
■ What caused it: A variant of Influenzavirus A (subtype H1N1) produced by a jump between species (it came from avian, swine and human strains), called H1N1 / 09. It spread to almost all countries as it had a very high contagion rate, but its lethality was not as strong as was feared at first.
■ Contagion and symptoms: The symptoms are similar to the common flu: fever, cough, itchy throat, muscle pain, headache, chills, nasal congestion, fatigue, and sometimes vomiting and diarrhea.
■ What happened: It was the last time that the WHO classified an outbreak as a pandemic before the Covid-19, and in view of the consequences, the Organization was criticized as alarmist and countries that bought large quantities of vaccines were considered to have exaggerated the importance of the outbreak. It began in Veracruz (Mexico) but it was the United States that identified, in April 2009, a new type of flu that spread rapidly around the world. The first year, in which the virus was most active, one in five people in the world was infected with this strain, although the mortality rate was lower than the most common flu and what experts had predicted. Children were the most affected group and people over 65 years of age, the least. Mexico was one of the worst hit countries, with more than a thousand victims.
■ How it was resolved: WHO admits that between 150,000 and 500,000 people died directly or indirectly from the outbreak. In Spain there were 271 deaths from influenza A in 2009. The indications to tackle it were similar to the current ones, although without confining the world population. The vaccine was prepared in record time the first year of the virus, which has not become extinct but has remained as seasonal flu.
MERS (Since 2012)
■ What caused it: the MERS-CoV virus.
■ Contagion and symptoms: It is a coronavirus that causes fever, cough and breathing difficulties that usually lead to pneumonia. It can also cause gastrointestinal symptoms, particularly diarrhea, although there are asymptomatic cases. It has a low contagion rate unless there is close contact, such as caring for an infected patient (most cases are attributed to person-to-person transmission in healthcare settings), but exactly how the virus is transmitted is unknown.
■ What happened: Suspected of coming from dromedaries. The WHO affirms that it does not know the role of these animals in the transmission of the disease, but infected dromedaries have been detected in countries such as Saudi Arabia, Egypt, Oman or Qatar.
The WHO reports that approximately 35% of MERS-CoV cases have resulted in the death of the patient.
■ How it was resolved: The initial outbreak in 2012 resulted in 2,494 cases (80% of them in Saudi Arabia, which is where the disease began) in 27 countries and 858 deaths, but there have been some outbreaks, such as the one in South Korea in 2015. There is no vaccine at the moment.