The global impact of coronaviruses has been significant. These viruses can cause a wide range of symptoms, including fever, cough, and pneumonia.
The World Health Organization estimates that a global pandemic caused by a new coronavirus could result in 6-11 million cases of severe illness and up to 1 million deaths. It can also have a large economic impact on healthcare systems.
COVID-19
COVID-19, or severe acute respiratory syndrome coronavirus disease 2019 (SARS-CoV-2), is a new viral pneumonia that has spread rapidly around the world. This disease, like SARS-CoV and MERS-CoV, has potential to cause serious illnesses that include damage to vital organs.
It can also be fatal. For example, it can lead to heart, liver, and kidney disease. The virus is highly transmissible, and it can mutate quickly to produce new infections.
Worldcoronaviras are a group of single-stranded RNA viruses that can cause respiratory illness in humans. They are considered a top global health threat.
Since the first cases emerged in China, the epidemic has spread to 117 countries and prompted a global response from the international community. This includes strengthening laboratory preparedness and capacity, implementing vaccination programs, and engaging with global partners to determine the safest ways for people to travel.
Many of these strategies and investments have been essential to rapidly respond to COVID-19 and save lives. However, as the outbreak unfolded, a number of data gaps and barriers to surveillance were identified.
One of the most significant challenges was lack of testing capacity. In the early stages of the pandemic, many countries were not able to test for COVID-19, which negatively impacted their case count estimates. In addition, the timing of testing was often a significant issue. It could mean that a patient is diagnosed with COVID-19 weeks after the onset of symptoms. This may have led to misleading case counts, especially for hospitalized patients.
These barriers to testing and reporting could be overcome, but it would require cooperation from the public health sector and government. As COVID-19 is a novel virus that requires specific reagents and equipment, this can be a challenge for many countries.
Aside from the technical challenges, COVID-19 has also had a profound psychosocial impact on people in affected countries. Children and their families have been deprived of kindergartens and schools, their social contacts are restricted, and their economic situation has worsened. Additionally, their fear of COVID-19 infection has influenced their behaviour and made them feel anxious.
SARS-CoV
Coronaviruses are a diverse group of viruses that can infect many different animals. They cause illness ranging from the common cold to more severe diseases, making them a new public health concern. Two coronaviruses that emerged in humans in 2002 and 2012, SARS-CoV and MERS-CoV, caused fatal respiratory infections.
SARS-CoV is a highly transmissible, zoonotic respiratory disease that has spread rapidly around the world in recent years. It has been linked to human-to-human transmission in China, and community transmission is believed to have spread the virus throughout Asia and to other countries worldwide9.
The first SARS-CoV cases were reported in Wuhan, China, in December 2019. Over a 10 month period, this respiratory disease caused a massive global outbreak. It has since killed over 6 million people worldwide.
Its origins are unclear, but it is believed to have a reservoir host. It may have originated in bats, which are known to be carriers of SARS-CoV and other sarbecoviruses. Other wildlife hosts that have been associated with SARS-CoV, such as pangolins, also appear to be possible reservoirs of the disease.
SARS-CoV has a phylogenetic cluster with four horseshoe bat coronaviruses (RaTG13, RmYN02, ZC45 and ZXC21) and novel pangolin coronaviruses identified in wildlife from Guangxi and Guangdong provinces39. The phylogenetic analysis shows that SARS-CoV is closely related to these horseshoe bat and pangolin coronaviruses, and its genome sequence is almost identical with those of a bat SARS-like coronavirus (ZC45)40.
Vaccines based on messenger RNA have been developed and are being widely used in some countries, with the goal of preventing SARS-CoV infection by stimulating the immune system to produce antibodies that bind to a protein called the nucleocapsid. However, currently used mRNA vaccines elicit antibodies to the spike protein rather than the nucleocapsid, which raises questions about how these antibodies will perform in areas with high vaccination coverage.
MERS-CoV
MERS-CoV is a new respiratory disease that was first discovered in Saudi Arabia in 2012 and is spreading to other regions around the world. The virus is highly contagious and can cause severe, life-threatening respiratory illness. Symptoms include fever, coughing and shortness of breath. Patients may develop pneumonia, which can be fatal if not treated quickly enough.
MERS is a zoonotic infection, meaning that people can get it by contact with infected animals, such as dromedary camels. The virus has been found in dromedary camels in several countries around the world and is thought to have a long history of transmission in these species.
The virus is a coronavirus with a spike protein that uses the cellular receptor dipeptidyl peptidase 4 (DDP4; CD26) to enter host cells. DDP4 is evolutionarily conserved across many animal species and is commonly expressed in lung and kidney cells. The virus has a wide range of possible hosts, but humans are unlikely to be a major reservoir.
Although the pathogenesis of MERS is unknown, research suggests that the virus attacks the immune system in several ways. Specifically, it reduces the induction of cytokines by inhibiting signal transduction cascades that trigger cytokine induction. It also has the ability to induce apoptosis, which is the death of healthy cells.
Infection with MERS-CoV occurs in a variety of clinical settings, but most infections are reported from hospital patients. Patients with MERS often have a recurrent fever and upper respiratory tract symptoms, such as non-productive cough and a sore throat. Symptoms usually progress to pneumonia within one week of infection.
Infection with MERS-CoV can be prevented by avoiding contact with dromedary camels. Similarly, individuals should avoid eating raw camel milk or camel urine, which may contain the virus. In addition, healthcare workers and other people who have had prolonged face-to-face contact with a suspected or confirmed MERS-CoV case should be monitored for fever and respiratory symptoms for 14 days after the last exposure.
Hendra virus
Hendra virus is an RNA virus that can be transmitted from bats to horses and sometimes to humans. This is called a’spillover event’ and can cause serious health problems.
Hendra is also known as the Brisbane equine disease virus, named after a suburb in Queensland, Australia where it was first identified. It is one of the world’s most lethal viruses, killing anywhere from 40% to 90% of infected animals and people.
A veterinary vaccine against Hendra is available in Australia, which can be given to healthy horses from 4 months of age. A booster dose is then given every 12 months.
The virus is thought to be passed between horses through contaminated water or food and by inhaling droplets of blood or saliva, via the nasal route. Symptoms usually develop within a few days of exposure, and the illness usually progresses to death.
Horses can be injected with a vaccine that contains a noninfectious protein component of the virus to prevent infection. This is available through accredited veterinarians in Australia and will prevent an acute onset of clinical signs that can lead to fatal illness.
The virus is a ‘notifiable’ condition in Australia and is monitored through public health units. If you think you have been exposed to a horse that has a virus, contact your local public health unit for further advice and to have the situation investigated.
Rous sarcoma virus
Rous sarcoma virus (RSV) is a type of retrovirus that produces tumors in various animals. It belongs to a group of viruses that have an RNA genome and produce tumors via oncogenes. It has been found to be oncogenic in mice, cats, and cattle.
RSV has a complex RNA genome that is expressed in eukaryotic cells and is translated by the host cell’s cellular machinery. However, the RNA genome is susceptible to quality control mechanisms called nonsense-mediated mRNA decay (NMD). NMD recognizes and targets mRNAs containing premature termination codons for degradation in the host’s translation machinery. This is a major limitation for some retroviruses, such as RSV, which encode enzymatic activities but rely on the host cell’s pool of proteins to produce progeny virions.
A cis-acting element within the viral genome, known as an RSV stability element (RSE), prevents the decay of full-length unspliced RNA in response to NMD. The RSE is located immediately downstream of the gag open reading frame and facilitates NMD evasion by avoiding the recognition and degradation of the mRNA.
In addition, the RSE facilitates splicing of the viral mRNA and thereby improves the rate at which the virus produces progeny virions. Additionally, the RSE can facilitate splicing of the viral mRNA into several different open reading frames, allowing for efficient genomic expression.
The RSE has also been shown to facilitate the assembly of virus-like particles. Gag deletion mutants exhibited the ability to form spherical virus-like particles in vitro and within Escherichia coli, indicating that the RSE is responsible for determining the shape of the particle. This is important because spherical particle assembly has been observed as a morphological determinant in the viral infection process and it may be involved in a mechanism of tumor formation by the Rous sarcoma virus.
