Charlotte Primeau

Biological Anthropologist,

Radiographer, Medical Researcher

Charlotte Primeau

Biological Anthropologist, Radiographer, Medical Researcher

When animals kill us with their diseases

by Feb 15, 20200 comments

The coronavirus has been making the headlines for weeks. The situation with the coronavirus continues to evolve  – and it is causing fear and anger – mainly from information mistrust and over information being withhold, allegations of scaremongering and quite possible – the lack of treatment options and preventative vaccines.

As front line staff working in a UK city hospital, if the coronavirus were to significantly enter the UK it is possible I could encounter it. I therefore decided to investigate the background of the coronavirus and other viruses and share what I found here.

So, what is the coronavirus? It is a large family of viruses that cause a range of illness from the common cold to more severe forms such as Middle East Respiratory Syndrome (MERS), Severe Acute Respiratory Syndrome (SARS) and the new strain originating in Wuhan, China. The current strain is called Novel coronavirus (2019-nCoV), called so because the outbreak started in 2019, the strain is novel, meaning not previous seen in humans and is of the corona family. What the coronaviruses also have in common is being a so called zoonotic disease, which mean it spreads from animals to humans once it has mutated to be able to infect humans. According to the WHO there are many more strains of coronaviruses circulating in animals that have not (yet) transferred to and infected humans.

It is not always clear how zoonotic diseases are transmitted from animals to humans. It can be through media such as air, respiratory, or from bites and saliva. However, a major factor in the transmission to humans is Bushmeat activity, which is when meat from wildlife species such as mammals (for instance monkeys or gorillas), reptiles, amphibians and birds are hunted in tropical forests. The animal-to-human transmission occurs during hunting or from the subsequent butchering and consumption.

Due to the unfortunate thorough cleaning of the animal market in Wuhan, China following the outbreak, scientist have not yet been able to identify which animal the 2019-nCOV virus originates from. Currently, based on genetic testing of the virus, it is suspected to derive from pangolins, long-snouted ant-eating animals. There are eight species of pangolins; four based in Africa and four based in Asia. The Chinese pangolin (Manis pentadctyla) is native to China.

Little is known about the current coronavirus, including infection and mortality rates (death rate).  How contagious a virus is, is measure in what is termed R0 (pronounced “R naught”), also called the reproduction number, as a virus reproduces itself while spreading to new people. R0 gives the average number of people being infected by a disease from a single contagious individual. This is for a population that is not vaccinated for the disease and who were previously free of that disease (as they will otherwise have natural immunity from prior outbreaks). If a disease has an R0 of 14, then one infectious person will transmit the disease to an average of 14 people. Currently the coronavirus is estimated to have an R0 value of between 2-3. For comparison SARS has an R0 value of 2-4, and Ebola has an R0 of 2.  Measles has one of the highest R0 numbers, often quoted to between 12-18.
The death rate of the 2019-nCoV is still not clear; but is currently estimated at about 2% of those infected. In comparison, the death rate of the common cold is about 0.05% in the US. The death rate from SARS is about 10% and for Ebola around 60%.

Lastly, the coronavirus is so far only categorized as an epidemic and not a pandemic. What is the difference? Well, an outbreak is defined as a higher occurrence of cases of a specific disease than expected in one area. An outbreak can last from days, to weeks or even several years.
An epidemic is a rapid outbreak of a disease that infects people normally for a week or two within a population. Examples of epidemic diseases are the SARS epidemic in 2003 that killed nearly 800 people, and the Ebola epidemic between 2013 and 2016 that killed more than 15,000 people.
A pandemic, on the other hand, is when a disease is spread worldwide. Historic cases of pandemics include smallpox, tuberculosis and the Black Death (the medieval plague). In modern time, we had the 2009 pandemic of swine flu, which killed 14,286 people worldwide.

Below is a compilation of diseases transferred from animals where humans have been killed in significant numbers:

Outbreak: 2002-2003
Origin: China
Animal: Palm civets (who possibly contracted it from bats)
Category: Pandemic
Mortality: 774 people
Death rate: 10%
Treatment: none, apart from supportive care
SARS originated in China and quickly spread to other Asian countries with cases in Canada and a few cases in other countries. Transmission is like flu, as an airborne virus, through droplets of saliva, coughed or sneezed by an infected person or from infected surfaces from unwashed hands. Time of infection to start of symptoms (called the incubation period) is about 2-10 days. Symptoms are similar to flu with fever, chills and shaking, shortness of breath and muscle aches. After these symptoms the infection will start to affect the lungs leading to further symptoms such as a dry cough, difficulties breathing and increasing lack of oxygen in the blood, which causes death in the most severe cases.

Outbreak: 2012
Origin: Saudi Arabia
Animal: Dromedary camels
Category: Epidemic
Mortality: 861
Death rate: 35%
Treatment: none, apart from supportive care
MERS was first noted in Saudi Arabia in 2012 and based on research suggested to originate from dromedary camels. Since, it has spread to 18 countries including Europe and the USA. Transmission is like flu, as an airborne virus, through droplets of saliva, coughed or sneezed by an infected person although it does not seem to be very contagious between people unless they are in close contact.  Incubation period is about 5-6 days after exposure but can but can range from 2-14 days. Symptoms are similar to flu with fever, chills and shaking, shortness of breath and muscle aches. After these symptoms the infection will start to affect the lungs leading to further symptoms such as a dry cough, difficulties breathing and increasing lack of oxygen in the blood, which causes death in the most severe cases. Some people are however symptomless.

Outbreak: 1976 and several since, especially in 2014-2016, 2018-2019.
Origin: North East Africa
Animal: Fruit bats
Category: Epidemic
Mortality: 15,246
Death rate: 60%
Treatment: none, apart from supportive care
Ebola was first seen in two smaller outbreaks in 1976 and then with two larger epidemics in 2014 and in 2019. Transmission is through direct contact with blood or objects contaminated from a diseased person with their body fluids (like blood, feces, vomit) or through infected breast milk when feeding infants.  People become infectious when symptoms start and remain infectious as long as their blood contains the virus. Initial symptoms are fever, muscle pain, headache and sore throat. This is followed by vomiting, diarrhea, rash, impaired function of the kidney and liver, and for some internal and external bleeding.

Origin: Africa
Animal: Monkey
Category: Pandemic
Mortality: About 32 million
Death rate: 44%
Treatment: No cure but antiviral medication can reduce the virus to undetectable levels
HIV was first recognized in patients in 1981. Subsequent genetic analysis of the virus from around the world revealed it was a retrovirus and there were two types: HIV-1 and HIV-2. HIV-2 is less likely to cause AIDS and is predominantly confined to people from West Africa. HIV-1consists of three distinct groups. Group N and O are rare and predominantly restricted to people from Cameroon and surrounding areas. Group M is the group that most people (about 98%) worldwide are infected with. Sexual intercourse is the main mode of transmission, but HIV can be transmitted through any of the following body fluids: blood, semen, vaginal and rectal fluids and breast milk.  Symptoms of infection with HIV may occur after 2-6 weeks after exposure as a short flu-like illness, although only 80% experience this. After this no other symptoms may be apparent for years, although the virus is slowly causing progressive damage to the immune system. This continues until the immune system is severely damage and can no longer fight infections.

The Spanish Flu (Bird flu)
Outbreak: 1918-1920
Origin: Unknown
Animal: Likely birds, infected from pigs
Category: Pandemic
Mortality: Uncertain, between 50-100 million
Death rate: Estimated to about 10-20%
The Spanish Flu is without doubt the biggest and deathliest pandemic of all times. It has been estimated that it killed 3-6% of the entire world population including people in remote locations such as Pacific Islands and the Artic. In 24 weeks The Spanish Flu killed more people that HIV have in 24 years during its three sweeps of pandemics during 1918-1920. The strain is a subtype of influenza A (H1N1) and is very similar to the H1N2 strain that cause swine flu in 2009. Initial symptoms were like the common flu with chills, fever, nausea, aches and fatigue with recovery after a few days. However, the second and third wave of the pandemic was severely fatal where the person suffocate from fluid in their lungs and lack of oxygen, while they turned blue and developed dark spots in their cheeks. When World War 1 was over, the Spanish Flu had killed more people than World War 1 and 2 combined.

Swine Flu:
Outbreak: 2009-2010
Origin: Mexico
Animal: Pig
Category: Pandemic
Mortality: Between 284.000 – 575.000
Death rate: 1-4%
Treatment: Two antiviral drugs although they are reserved for people who are at high risk for complications from the flu to avoid drug resistance.
The 2009 flu pandemic was the second pandemic involving the H1N1 influenza virus and for this outbreak was termed the H1N2 strain. The transmission is like that of other flu and influenza types and with similar symptoms. Incubation period is about 1-4 days and the infected person is contagious from about a day before symptoms show to about 5-7 days after onset of symptoms. The outbreak was not as serious as originally suspected, mainly because a significant proportion of especially elderly people were already immune to it. The rapid spread if the disease was mainly cause by young people who were not immune to the disease and death was caused by respiratory failure. This strain of flu is not protected by the seasonal flu vaccination.

Although, little is still known about the coronavirus, it does seem that it is not highly contagious or has an especially high death rate compared to many other infectious diseases. I believe the challenge with the coronavirus is the muddle of media information. Through the general media and especially social media the disease has been highlighted so people are aware of its presence and spread and hence the need to protect themselves and others from continuous spreading. However, social media above all has created a heightened fear and spread of wrongful information about it being a pandemic explosion of a new disease that is running amok throughout the world, which is not yet quite the case. But, on the other hand, it is quite possible this dire messaging is having a positive effect in ensuring that the public takes corrective measure to ensure containment, management and minimum spread of the coronavirus.

References for images:
Front page: The coronavirus: Alfred Pasieka/Sceince Photo Library via Getty Images.