Comparison of COVID-19 Health Risks With Other Viral Occupational Hazards

The European Commission periodically classifies viruses on their occupational hazards to define the level of protection that workers are entitled to claim. Viruses belonging to Groups 3 and 4 can cause severe human disease and hazard to workers, as well as a spreading risk to the community. However, there is no effective prophylaxis or treatment available for Group 4 viruses. European trade unions and the Commission are negotiating the classification of the COVID-19 virus along these 2 categories. This article weighs the reasons to classify it in Group 3 or 4 while comparing its risks to those of the most significant viruses classified in these 2 categories. COVID-19 characteristics justify its classification in Group 4. Contaminated workers in contact with the public play an important role in disseminating the virus. In hospitals and nursing homes, they increase the overall case fatality rate. By strongly protecting these workers and professionals, the European Union would not only improve health in work environments, but also activate a mechanism key to reducing the COVID-19 burden in the general population. Admittedly, the availability of a new vaccine or treatment would change this conclusion, which was reached in the middle of the first pandemic.

The European Commission periodically classifies viruses on their occupational hazards -that is, the risks they entail for workers. This classification defines the level of health and safety protection from exposure to viruses at work that workers are entitled to claim. Viruses belonging to Group 3 can cause severe human disease and hazard to workers, as well as a risk of spreading to the community, but there is usually effective prophylaxis or treatment available. Group 4 viruses are similarly defined, except there is usually no effective prophylaxis or treatment available. 1 The last classification dates October 31, 2019. 2 The European trade unions and the European Commission are negotiating the classification of the COVID-19 virus along these 2 categories. This article weighs the reasons to classify it in Group 3 or 4 while comparing COVID-19 risks to those of the most significant viruses classified in these 2 categories. Beyond the degree of protection that it justifies, the usefulness of the comparison stems from the fact that it makes it possible to weight various epidemiological and medical indicators from a public health perspective.

Methodology
We compared the mortality, morbidity, and transmission in the general population and in workers/professionals exposed to the COVID-19 virus to those of viruses belonging to Groups 3 and 4 and having sufficient public health importance to deserve a chapter in 2 well-known handbooks of infectious diseases 3 and tropical medicine. 4 We also examined the hypothesis that contaminated workers in contact with the public not only increase COVID-19 transmission and case fatality rate (CFR) in their work environment but also, importantly, in the community.
Effective treatment reduces suffering, sequellae, and CFR. Prophylaxis reduces incidence and particularly R0 5 in case of human-to-human transmission, and sometimes CFR as well.
Transmissibility is measured by the household secondary attack rate (SAR). The SAR is the probability that an exposed susceptible person develops the disease over the duration of infectiousness in a case of patient. The R0 basic reproduction number of an infection is the expected number of cases directly generated by 1 case in a population where all individuals are susceptible to infection. 6 R0 is the product of virus transmissibility by the number of contacts over contagiousness period by the duration of this period. The proportion of population to be vaccinated to achieve herd immunity is given by the following formula: P T to be vaccinated ¼ ð1 À 1=R0Þ Â 100 R0 is the index at the start of the epidemic at time t0 when collective immunity is zero. Then we talk about R e at time t. For example, for COVID, R0 was between 2 and 3 and is now between 0.5 and 0.7 in Belgium following confinement. 7 The (population-based) disease-specific mortality is the product of the CFR by the incidence.
We aimed at assessing the public health importance of the considered diseases in Europe, particularly their direct importance for workers and professionals, and the indirect importance of their infection for community health while testing the hypothesis that workers in contact with the public increase the COVID-19 R0 and its CFR in specific milieux and/or the community.
The most important criterion is the existence of effective prophylaxis and treatment. The second is virus presence in Europe. The third is its population-based mortality, followed by the remaining criteria. Because all viruses can contaminate lab workers, their case is not discussed here.

Results of Epidemiological Comparison of COVID-19 With Other Viruses of European Commission Groups 3 and 4 of Significant Public Health Importance
For each disease, we examine the prevention, R0, incidence, CFR, general mortality, occupational concentration, and importance in Europe.

COVID-19
• No vaccine is available. Prevention relies on the use of masks, 8 testing, tracing contacts, and isolation. With regard to treatment, Remdesivir would reduce the sickness episode duration, but its effect on the risk of dying was not demonstrated in 1 study 9 and, according to another, this effect would be moderate. 10 Hydroxychloroquine in hospitalized patients with COVID-19 would not be effective, 11 but it is too early to hold definitive conclusions as it is a combined treatment (hydroxychloroquine þ azythromycin) that would have yielded the results in Marseilles and, furthermore, it has been advocated for early uses. • It is too early to determine the maximum R0 of the epidemic ( Figure 1). • As of May 10, 2020, there were 3,986,119 cases and 278,814 deaths; and 15,685,177 cases and 637,231 deaths as of July 24, 2020. 12 • The CFR was quite variable according to country (Table 1). 13 Notice that during an outbreak of a pandemic, the CFR is a poor measure of the mortality risk of the disease because the denominator tends to increase more rapidly as more people are tested. Intercountry comparisons are also misleading, especially between small and large countries, because in large countries the epidemic concentrates regionally 14 and because of large differences in testing capabilities, leading to the impossibility of knowing the actual numbers of cases, most of them being asymptomatic. Excess deaths (as a percent above normal, established on the average of 5 previous years) is a better indicator. • Early testing, tracking, contact tracing, isolation, and quarantine explain part of the impact in Germany (3% excess deaths against 72% and 56% in the United Kingdom and Spain, respectively; see Table 1), as do the number of intensive care unit beds per 100,000 population (33.9 in Germany, 15.9 in Belgium, 12.5 in Italy, and 9.7 in Spain). 15 Hypothetically, this difference could explain why nursing home residents were more easily hospitalized in Germany: The proportion of COVID-19 deaths in nursing homes would increase when the capacity of intensive care units is reduced. • As with CFR, it is too early to compute the diseasespecific mortality rate. However, it can already be observed that mortality in the countries where it is the highest is explained by poorer planning of epidemic control (tracing, testing, isolation, masks) and by a hospital system and nursing homes whose resources have been cut by austerity policies or that are insufficiently accessible because of the commercial financing of health systems 16 -good planning possibly compensating partially for the other factors. Geographical, demographical, social, economic, political, and cultural variations from country to country can also explain part of the differences in the epidemic transmission (R0), thereby affecting incidence and mortality. • What are the reasons to believe that workplaces are important to the dissemination of COVID-19 in the general population? Health care 17 and nursing home workers are well-known disseminators in high-risk populations. Sixty-one percent of people with COVID-19 investigated in New Zealand clusters were in work environment clusters ( Table 2). 18 In Belgium, as of May 5, 53% of deaths occurred in residential homes for the elderly, against 47% in hospitals. 19 Moreover, the CFR in residential homes for the elderly was 54.7%. (In order to be as complete as possible in reporting the pandemic, the Belgian government includes suspected cases in its deaths count. By April 15, the total number of reported deaths since the beginning of the pandemic was 4,440. The confirmed cases were almost exclusively those in the hospitals and reached 2,264 so far.) While the government restricted parents' access to these homes, it allowed positive-tested workers and professionals to continue working there. The distribution of cases in Germany ( Figure 2) shows a higher incidence in the working-age population than in the 60-80 age group and a steep increase in the age groups at retirement homes. The moderately higher incidence in females could mirror their higher presence in social services. Occupational risks for COVID-19 were recognized early on. 20 Finally, a large array of publications suggest that there is a disproportionate COVID-19 burden on working classes in every country where it has been investigated -for example, in France 21 and Korea. 22

Rift Valley Fever
• Rift Valley Fever 28 (RVF) surveillance, tracking, contact tracing, and isolation are effective. • R0 is low, the human-to-human transmission being quite limited. • The biggest epidemics were comparatively modest (Sudan, 2007, 738 cases) because epidemics tend to be self-limiting. • CFR was 4% in Sudan.
• RVF mortality is low.
• RVF-specific mortality primarily concerns workers in contact with dead animals. • RVF does not occur in Europe. Although currently confined to Africa and the near East, this disease causes concern in countries in temperate climates where both hosts and potential vectors are present, such as the Netherlands. 29

Rabies
• Rabies 30,31 post-exposure vaccination and immunoglobulin are effective. Prevention with dog immunization is effective. • There is practically no human-to-human rabies transmission. • Worldwide, the disease burden is significant, with 15 million cases per year. • Without treatment, rabies is always fatal (CFR ¼ 100%). • Worldwide, mortality was 17,400 per year in 2015.
• There are no occupational clusters.
• In 2013, no cases were reported in the European Union, but 3 were reported in the European Economic Area (Russian Federation). 32

SARS
• No vaccine and treatment exist for SARS. 33

MERS
• There is no treatment and no vaccine. 36 • The R0 is 2.5-7. 37 • During the 2012-2013 epidemic, 75 severe cases were recorded. The number of mild cases was unknown. • The CFR was 65%.
• There were 49 deaths during the 2012-2013 epidemic. 35 • Occupational concentration in health and social services could be expected. • There have never been MERS cases in Europe. Poliomyelitis Type 1, 2, 3 • The vaccine is effective. 38 • Poliomyelitis is a highly contagious disease (R0 ¼ 6). 5 • Type 2 was declared eradicated in 1999. There have been no Type 3 cases since 2012. In 2019, 175 cases of Type 1 were reported. One per 200 cases leads to irreversible paralysis. • Of those with paralysis, 5%-10% die.
• There are no occupational polio clusters.
• Europe was declared polio-free in 2002. 39 Hepatitis B • The vaccine and Tenofovir treatment are effective. 40 • Hepatitis B (HBV) is highly contagious. Its R0 is 5 when there is no intervention.

Japanese Encephalitis
• Immunization is effective. 51 • Children are the main transmitters.
• Worldwide, there are 68,000 cases per year.
• The CFR is 30% of severe cases.
• There is no occupational concentration.
• The disease is not present in Europe.

West Nile Virus
• Physical protection of workers is effective. There is no treatment (although supportive treatment is available) and no vaccine. 52

Influenza H5N1 (Avian Flu)
• If there is no available vaccine, the oseltamivir treatment is effective, as is surveillance. 69

Chikungunya
• There is neither prevention nor treatment available. 72 • The disease is transmitted by an Aedes-type mosquito. There is no human-to-human transmission. • Overall, 1.9 million cases have been declared in Asia since 2005. • The CFR is 0, but the disease is a death cofactor in the elderly. • Mortality is almost zero.
• The disease has no occupational concentration.
• The disease is not present in Europe. 73

Ebola
• As far as prevention is concerned, the rVSV-ZEBOV vaccine was successfully used in the Democratic Republic of the Congo 2018-2019 outbreak. Surveillance, contact tracing, and quarantine are effective. A multidrug therapy is being tested. Supportive treatment is moderately effective. 74 • R0 has been 1 to 1.3 75 and even 1.5. 76,77 • With regard to incidence, 29,000 cases occurred in Sierra Leone, Liberia, and Guinea during the 2014-2016 epidemic. Of these, 27% of infections were asymptomatic. 78 • CFR is 50% (25%-90%).    • There were 11,500 deaths during the Sierra Leone, Liberia, and Guinea epidemic in 2014-2016. • The greatest risk of secondary attack is in nursing care and health care services in general. • Only a few imported cases occurred in Europe (primarily health professionals contaminated in Africa and treated in Europe).

Marburg Hemorrhagic Fever
• There is no prevention and no treatment. 79 • The R0 is 1.59. 80 Primarily bats transmit the disease, but there is some human-to-human transmission.

Smallpox
• The vaccine is effective. 81 • The disease had a primarily inter-human transmission, but it could also be spread through direct contact with infected bodily fluids or contaminated objects, such as bedding or clothing. R0 was 4.5. • With regard to incidence, the last case succeeded in Somalia in 1977. The disease was declared eradicated in 1980. • CFR was 4.5.
• There was no occupational concentration.

Lassa Fever
• There is no vaccine. Ribavirin is an effective treatment if taken early. 82 • Infection is acquired through contact with an infected rodent, but person-to-person transmission is possible (R0 was 1.

Discussion
The list of studied viral pathologies may be incomplete from a public health significance perspective. The provided statistics only give an order of magnitude, and this is how we used them to draw our conclusions, especially since it is too early to estimate the R0 and CFR of COVID-19. In addition, countries declare the disease heterogeneously. Some demand a test, others suggestive symptoms, while others do not count deaths in nursing homes. Data on the period-to-period difference in mortality between 2020 and previous years are only beginning to emerge; to enable inter-country comparisons, the COVID-19 mortality will have to be assessed through excess mortality rates, by comparing overall countryspecific, monthly mortality rates to the previous 5-year average mortality rate of the same month.
Pooled mortality estimates from the EuroMOMO network continue to show a markedly increased level of excess all-cause mortality overall for participating European countries, coinciding with the current COVID-19 pandemic. This overall excess mortality is driven by a very substantial excess mortality in some countries, while other countries have had no excess mortality. The mortality excess is primarily seen in the age group of !65 years, but also in the age group of 15-64 years. For the EuroMOMO network as a whole, from Week 10 in 2020 and as of Week 18, there were 149,447 excess deaths estimated in total, including 137,524 in the age group !65 years and 11,573 in the 15-64 years age group. This time period includes part of the influenza season as well as the start of the COVID-19 pandemic. 85 Comparisons between mortality of epidemic diseases (such as COVID-19) and chronic ones (such as HCB or HCV) can be misleading, especially because we do not know yet if COVID-19 will provoke new waves or possibly mutate and be periodically recurrent.
In general, data quality is much lower in low-to middle-income countries, as are CFRs, because of limited access to high-quality health care. Some diseases, such as HVB and HVC, are known to be heavily underdiagnosed. With regard to COVID-19, several countries are reluctant, for political reasons, to publish honest data that allows for comparison.
As we are still in the middle of the first pandemic of COVID-19, the comparison should be made with caution. Table 3 summarizes our findings.

Unger
Among the studied diseases in Group 3, HVB and HVC (Hepatitis B and C), H2N2, and HIV (AIDS) represent a public health risk to E.U. citizens. The others are either absent or exceptional in Europe. HBV, HBC, H2N2, and HIV, however, have an effective treatment and/or prophylaxis -unlike COVID-19. On this criterion, the key one that distinguishes Groups 3 and 4, COVID-19 should be classified in Group 4. Another key reason is that it represents a bigger public health threat to E.U. workers, professionals, and population: In Europe, COVID-19 has killed in 3 months more than 65 times the number of people killed in 1 year by AIDS, 3 times more than HBV, and 2.3 times more than HBC. H2N2 has been silent for 60 years. All Group 3 viruses, present in Europe or not, have a total mortality inferior to COVID-19. Poliomyelitis, HBV, and AIDS have a higher R0 in the rest of the world but not in Europe. Untreated, 5 type 3 viruses have a CFR higher than COVID-19.
By contrast with COVID-19, 3 of the 4 diseases belonging to Group 4 have an effective treatment and/ or vaccine. On this criterion alone, COVID should be classified within Group 4. Furthermore, the COVID-19 R0 exceeds the Ebola R0 in early epidemics -that is, in situations unaffected by prophylactic interventions.
What would be the consequences on COVID classification if Ebola, Lassa, and Marburg fevers were actually found in Europe? Basically, our conclusion would remain valid because the COVID-19 R0 is superior to the R0 of these pathologies and their incidence is so low that although their CFR is superior, the mortality of these 3 diseases would remain vastly inferior to the COVID-19 mortality.
While most of the studied viruses concentrate on health care workers and workers in contact with animals, COVID-19 has a wide distribution that concerns jobs in essential sectors (nurses, midwives, physicians, caregivers, child minders, home helpers, paramedical professions, social work and guidance professionals, army, police, firefighters, cashiers, etc.). Many more, particularly precarious workers, are at risk in nonessential, recreational sectors, such as restaurants, gyms, and shopping malls.
In conclusion, COVID-19 characteristics justify its classification in Group 4. Furthermore, and importantly, with effective protection of workers and professionals (particularly in health care services, nursing homes, and social services, although not limited to these sectors), the European Union would not only improve health in work environments, but also activate a mechanism key to reducing COVID-19 transmission, morbidity, and mortality in the general population. In public health terms, the strongest worker protections would be a highly cost-effective intervention. In economic terms, it would probably be a highly cost-beneficial intervention.
Admittedly, the availability of a new vaccine or treatment would imply a change in the proposed classification.

Author's Note
Having worked in an emergency, the literature review has been superficial. We were unable to present the bibliography in a scientific manner. Online articles were accessed between May 1-10, 2020. We apologize to our readers for possible errors in the document.