Three years ago, the director general of the World Health Organization (WHO) reported on a new coronavirus, which had been identified for the first time in China and which had spread to the point of becoming a public health emergency.
WHO maintains a list of viruses and bacteria with pandemic potential. Jill Weatherhead of the Baylor College of Medicine said prioritizing diseases is generally based on two factors: their ability to spread and the ability of humans to treat them.
This list helps guide scientists, governments, and organizations in investing energy and funds to study the most susceptible pathogens. WHO develops “blueprints” with strategic objectives and research priorities for each disease on the list.
According to the NPR, a revised list is expected to be published in the coming months. At the end of 2022, WHO met with more than 300 scientists to evaluate and update the list still in force. On that list there are nine diseases that keep epidemiologists awake at night, starting with Nipah virus.
This disease is carried by bats and domestic animals – such as pigs, horses, cats and dogs – which transmit it to humans. The latter can then disseminate it among themselves. Its mortality rate ranges from 40% to 75% and the virus can cause encephalitis.
Currently, there is still no vaccine against the Nipah virus, neither for animals nor for humans. Monoclonal antibody therapies are under development.
Outbreaks of the disease occur nearly every year in parts of Asia, but there are ways to prevent it: avoiding exposure to sick bats and animals; avoid the fruit consumption that bats may have nibbled on and not drink fruit juices that bats feed on. The risk of international transmission can be lessened by carefully washing these fruits and peeling them before eating.
The second disease is Crimean-Congo hemorrhagic fever. Humans usually catch the virus through contact with infected ticks or livestock. To transmit the virus between humans there must be an exchange of blood or body fluids.
Its mortality rate ranges from 10% to 40%. The disease is endemic, which means that it occurs regularly, in Africa, the Balkans, the Middle East and Asia. The virus causes severe outbreaks of fever and severe bleeding, and can damage the organ and cardiovascular system.
Although a vaccine is being used in Bulgaria, no research has been published on its working and it is not licensed anywhere else. Other vaccines are in development, and an antiviral drug called ribavirin appears to help treat infections.
It is difficult to know when an animal is infected. and must be avoided. The WHO says ticks that carry the virus are numerous and widespread. The threat can be reduced by avoiding tick bites and by wearing gloves and other protective clothing when handling livestock.
The third disease is Lassa fever, carried by rats and other rodents. The virus is endemic in parts of West Africa. Rats excrete the virus and humans pick it up when exposed to rodent urine and feces, either through direct contact or through eating contaminated food.
It can also spread between humans through direct contact with the secretions of an infected person (blood, urine, feces), through sexual contact and in medical settings.
The mortality rate varies between 1% and 15%. can be deadly for fetuses in the third trimester of pregnancy. In addition to death, a common complication is deafness, which can be permanent. There is no vaccine yet, but ribavirin appears to help treat infections.
As the main method of transmission is exposure to a certain type of rat, the potential for the disease to spread is limited to countries where rats exist.
Me and rift valley fever It is carried by mosquitoes. Insects can transmit the virus to both humans and their own offspring. Cattle, sheep, goats, buffalo and camels can also be infected. It spreads to people through contact with blood, body fluids or tissues from infected animals.
Although the mortality rate is less than 1% and the disease is mild for most people, about 8% to 10% of those infected develop severe symptoms, including eye lesions, encephalitis and hemorrhagic fever. Although a vaccine has been developed, it is not yet licensed or available.
Rift Valley fever spread from Africa to Saudi Arabia and Yemen. Floods seem to contribute because infected mosquitoes spread after heavy rains. Rapid case detection, including laboratory testing, has limited recent outbreaks.
O the Zika virus it is also carried by mosquitoes, also passing from the mother to the fetus, through sex and blood transfusions. It is rarely fatal, but it can cause severe brain defects in fetuses, including microcephaly. It has also been linked to miscarriage, stillbirth and birth defects.
There is neither vaccine nor treatment. So far, it is largely limited to areas where Zika mosquitoes live.
O Ebola and the Marburg virus. It is believed that bats and primates carry the viruses and that both spread the same way. After initial contagion from an animal, humans spread viruses to each other through direct contact with blood or body fluids. Viruses can also spread through contaminated objects or surfaces.
The average fatality rate is around 50%, although rates have ranged from 25% to 90% in previous outbreaks.
Were used Ebola vaccines in Guinea and in the Democratic Republic of Congo. Monoclonal antibodies approved by the FDA in 2020 could also help in the treatment of Ebola. Vaccines for Marburg virus are under development.
These viruses can spread quickly in healthcare settings, especially when sterilization is inadequate. However, the disease only spreads when a person is symptomatic, which facilitates control.
A MERS (Middle East respiratory syndrome) is carried by camels. After the initial camel-to-human spread event, this coronavirus spreads from person to person through close contact.
The recorded mortality rate is 35%. Several vaccines are in development, but none have been approved. Since 2012, 27 countries have reported infections. The coronavirus that causes MERS grows deep in the airways, making it less likely to be transmitted through sneezing and coughing.
As for the SARS (severe acute respiratory syndrome), palm civets were largely blamed for the 2003 outbreak. Bats and possibly other wildlife also carry it.
After the initial event of animal-to-human spread, SARS can spread between humans through close contact. It is believed to spread normally through droplets from coughs and sneezes and sometimes through surfaces. Its mortality rate is less than 1%.
No treatment or vaccine has been approved. Unlike SARS-CoV-2, which can spread before people know they are infected, this virus is usually spread only by symptomaticmaking its containment much easier through public health measures.
And finally disease X. The WHO says it does not classify diseases in order of potential threat, but recognizes the possibility that an as-yet-unknown disease could cause a serious pandemic.
In her work with bat viruses, for example, Raina Plowright of Cornell University has indicated that even in the small proportion of species studied, these animals carry thousands of viruses.