Coronavirus: contagion, transmission, symptoms, severity, incubation, R0

The term ” coronavirus ” in microbiology refers to a genus of RNA viruses of the Coronaviridae family, with pericapsid with a genome ofsingle filament with positive sense and a nucleocapsid of helical symmetry. Its genomic size ranges from around 26 to 32 kilobases, the largest of the RNA viruses. To date, 7 coronavirus strains capable of infecting humans are known:

  1. Human Coronavirus 229E (HCoV-229E)
  2. Human Coronavirus OC43 (HCoV-OC43)
  3. Human Coronavirus NL63 (HCoV-NL63)
  4. Human Coronavirus HKU1 (HCoV-HKU1)
  5. Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)
  6. Middle Eastern Coronavirus Respiratory Syndrome (MERS-CoV), also known as  Novel Coronavirus 2012 (2012-nCoV)  and  Human Coronavirus Erasmus Medical Center / 2012 HCoV-EMC / 2012
  7. Coronavirus 2019-nCoV (2019-nCoV).

The latter is what we often hear about these days and which we will discuss in the next paragraph.

ATTENTION: the data on the coronavirus 2019-nCoV are still incomplete, therefore some of the information contained below may be incorrect.

IMPORTANT: if you experience suspicious flu symptoms, such as fever, cold, sore throat and cough or if you have frequented suspicious people and places, DO NOT go to the emergency room, but call the emergency number 112 . For any information, the national reference number, established by the Ministry of Health, is 1500 . The call is free from landlines and cell phones, and the line is active every day from 8 to 20. In addition to 1500, in case of symptoms, it is advisable to call 112.

Coronavirus 2019-nCoV

The coronavirus 2019-nCoV is a virus belonging to the betacoronavirus genus (and coronavirus family) discovered around the end of the year 2019. The virus was genomically sequenced after a nucleic acid test carried out on a sample taken from a patient affected by a pneumonia during the 2019-2020 outbreak in Wuhan. Although it is assumed that the first infections occurred a few months earlier, the first 59 suspected cases were registered in China between the end of December 2019 and the beginning of January of the following year and among these the infection was confirmed in 41 patients. This virus is compared to SARS and has a still uncertain mortality rate due to the transitory phase of contagion still in progress:many of its characteristics are not yet clear and, although its ability to transmit from man to man has been ascertained, uncertainties still remain on the exact transmission modes – probably air – and on its pathogenicity. The 2019-nCoV coronavirus causes various symptoms, including high fever, cough, breathing difficulties . In severe cases, the infection can cause pneumonia, severe acute respiratory syndrome, renal failure, loss of consciousness, coma and even death , as happened also in Italy , especially in already debilitated subjects (for example elderly, immunodeficient and with others serious pathologies).

Other names

The 2019-nCoV coronavirus  is also called ” 2019-nCoV ” by the World Health Organization and is also known as ” Wuhan coronavirus ” or as ” COVID-19 ” or ” new SARS ” or ” Chinese coronavirus “. Another synonym often used is ” SARS-CoV-2 ” (acronym from English “severe acute respiratory syndrome coronavirus 2″, ie ” coronavirus 2 of severe acute respiratory syndrome “, to distinguish it from ” SARS-CoV ” (acronym from English Severe severe respiratory syndrome coronavirus) which in 2003 killed 775 people worldwide.

Transmission

The transmission of coronaviruses among humans in general takes place mainly through the respiratory droplets emitted by an infected individual through coughing or sneezing which, subsequently, are inhaled by a healthy person who is nearby. It is not clear whether it is possible to become infected even after touching surfaces or objects where the virus is present and subsequently bringing your hands towards your mouth or towards your nose or eyes. The 2019-nCoV coronavirus seems to be transmitted mainly by air (coughing and sneezing) and by contact with contaminated objects. The 2019-nCoV coronavirus would appear to be able to survive on surfaces for over a week, probably 9 days. Although respiratory viruses are usually transmissible when the sick person also presents symptoms, it would seem that the 2019-nCoV coronavirus can also spread during close contact with an asymptomatic patient.

Incubation

The coronavirus 2019-nCoV has an incubation period of 14 days , which means that – after being infected – the first symptoms will occur after two weeks and in these two weeks you are totally asymptomatic but you can transmit the virus to other people without knowing it.

ATTENTION: according to some theories, the incubation period would instead be 21 days.

Quarantine

Given the incubation period, therefore the quarantine period is two weeks : once this period has passed, if the symptoms have not occurred, it is certain that the person placed in quarantine is not contaminated and can return “free”.

Symptoms and signs

Patients infected with the 2019-nCoV coronavirus, after infection and a 14-day incubation period, experience gender symptoms and initial signs similar to those of a flu, including:

  • general malaise;
  • fever (in over 90% of cases). The fever is generally high, above 38 °;
  • dry cough (over 80% of cases);
  • tiredness (about 70% of cases);
  • shortness of breath (about 20% of cases);
  • dyspnoea, i.e. difficulty breathing (about 15% of cases);
  • leukopenia (deficiency of white blood cells);
  • lymphocytopenia (lymphocyte deficiency);
  • anorexia (loss of appetite).

In the later stages and in the most severe cases, the following may occur:

  • weight loss;
  • severe fatigue (severe lack of strength);
  • pneumonia;
  • acute renal failure;
  • coma;

Patients more at risk of greater seriousness and death

Not all patients necessarily experience severe symptoms and signs, but only those most at risk. The subjects most at risk and where there is a higher mortality are:

  • pregnant women;
  • elderly (especially over 80 years of age);
  • children;
  • subjects already debilitated for other diseases, in particular respiratory and cardiac;
  • people with compromised immune systems (for example with AIDS).

The fact that children are subject to risk is currently controversial: according to some, young age would in fact be a protection factor for infection and not a risk.

How many people develop complications?

Currently it is estimated that around 10-20% of total patients develop serious complications and symptoms . The remaining 80 – 90% do not develop severe symptoms and generally heal in a few days ( typically between 3 and 7 days ), as is the case with normal flu.

Mortality

The exact mortality is currently unknown, but it is estimated to oscillate between 0.7% and 2% of the sick, which means that (in the worst case) 2 out of 100 infected will die from the virus, while 98 infected people will NOT die . However, the majority of the deceased are already debilitated individuals. To make a comparison, the mortality from the seasonal flu of 2019 was 0.007%, however it is important to remember that for the flu of 2019 there was a vaccine that instead does not yet exist for the 2019-nCoV coronavirus.

IMPORTANT: 2% of mortality refers to the infected population and not to the entire population.

R0

By ” R0 ” is meant the ” basic reproduction number ” which represents the average number of secondary infections produced by each infected individual in a completely susceptible population, that is, never coming into contact with the pathogen. This parameter measures the potential transmissibility of an infectious disease. Ever since the 2019-nCoV coronavirus epidemic in China began to spread, the World Health Organization (WHO) and numerous research institutes around the world have estimated thatthe R0 of the infection should be between 1.4 and 3.8 in the areas affected in this first phase of viral spread. In other words, it means that on average, a single 2019-nCoV coronavirus patient will infect about 1 to 4 people . Obviously the higher the R0 value and the higher the risk of rapid spread of the epidemic and an R0 which is worth almost 4 would certainly be quite worrying, in particular for the difficulty, on the part of the National Health System, to manage a number of access to the emergency room and hospital admissions which increases rapidly in a very short period of time, exceeding the seasonal average that healthcare personnel are “used to managing” . For comparison, the 2019 seasonal flu R0 was 1.3.

Cure and vaccine

There is currently no vaccine or specific cure. Antibiotics are unnecessary.

Avoid alarmism

To avoid excessive and unmotivated alarmism, it is important to underline the fact that the deaths related to the infection generally concern elderly people who are already debilitated by other pathologies  and that therefore everything suggests that  the infection is much less serious than you think , at least for what concerns immunocompetent and non-debilitated individuals. At present, from a statistical point of view, the “normal” pneumonia would seem, for example, to be much more dangerous than the 2019-nCoV coronavirus infection. The majority of deaths in Italy in particular concern people who were already hospitalized for pathologies preceding the infection and currently we do not know for sure if the virus is the real cause of the death of these people or that it has only accelerated a process which is in itself inevitable.

Prevention

General tips to prevent infection are:

  • wash your hands frequently and thoroughly for at least 30 seconds and with high quality soaps;
  • do not touch your nose, mouth and eyes with your hands;
  • consume only quality food and not from China or other contaminated places;
  • cooking food, avoiding eating it raw;
  • drink bottled water;
  • avoid crowded places, such as subways and buses and avoid gathering places such as live and dead animal markets;
  • avoid sharing toothbrushes, cigarettes, kitchen utensils, towels, clothes and other potentially contaminated objects with people at risk;
  • avoid close contact with the sick or, if these measures cannot be taken, cover the nostrils and mouth with a mask;
  • avoid coughing or sneezing without covering yourself with a tissue or in the absence of this it is advisable to cough in the hollow of the elbow and in any case always away from other people;
  • pay attention to the typical symptoms of the infection, which include fever above 38 °, cough and breathing difficulties (in severe cases and in already debilitated individuals, the infection can cause pneumonia, severe acute respiratory syndrome, renal failure and death).

 

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