Bird flu 2024. How contagious is it and what is the risk of it spreading

Bird flu cases in 2024 in the US

Bird flu spreads among US cattle, a surprising development that worries scientists. Although there is no evidence that the virus can a human epilepsythe authorities are closely monitoring the situation.

Bird flu is a viral disease that affects birds and sometimes other animals such as foxes, seals and otters. The main strain is H5N1, which appeared in China in the late 1990s.

Bird migration has caused outbreaks in both domestic and wild birds, and human infections are rare. Scientists believe the risk to humans is low because bird-to-human transmission is rare and human-to-human transmission is not constant.

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H5N1 is now spreading rapidly in US dairy herds, described by the Centers for Disease Control (CDC) as “ongoing revolution in several states”.

The appearance of the virus in cattle surprised scientists, who thought that this disease could not affect cattle.

It comes amid another unusual development: in early June, a 59-year-old man died in Mexico from another type of bird flu – H5N2 – that had not previously been recorded in humans. It is not known how he contracted the virus, although there have been cases on poultry farms in Mexico.

Health organizations such as the World Health Organization and the CDC consider the overall risk to public health to be low. However, scientists insist that the spread of the virus must be closely monitored.

Professor Sir Peter Horby, director of the Institute of Pandemic Sciences at the University of Oxford, says these developments should be considered a wake-up call. H5N1 has been on scientists’ radar for years, spreading across continents and causing thousands of outbreaks in poultry and wild birds.

Outbreaks have also been reported in animals raised for fur, including mink. At the end of 2023, in Peru, more than 5,000 sea lions died from the virus, and direct contact with infected wild birds is believed to be the main cause. The virus has also been found in foxes, bears, otters, raccoons, goats and others.

Dr Ed Hutchinson, from the MRC-University of Glasgow Center for Virus Research, says that the virus is constantly changing, which is why it is being closely monitored.

The recent increase in bird flu has been particularly damaging to protected seabird species. Influenza viruses are known for their ability to mutate and acquire new genes as they move between hosts.

The spread of the virus in cattle was a real surprise, according to Dr Hutchinson. An event in animals raised by humans, and therefore close to them, is a cause of great concern.

Scientists now believe that transplants are ‘artificial’ – cows do not pass the virus to each other naturally. The virus can spread through contaminated milking equipment. Dr Thomas Peacock from the Pirbright Institute explains that although the virus does not spread naturally from animal to animal, spreading in dairy herds could increase the chances of it mutating in a way that allows it to, writes BBC.com.

Although pasteurization kills the virus, it is estimated that about 5 percent of Americans consume raw, unpasteurized milk. In Canada, scientists have also started testing milk.

How contagious it is

Migratory waterfowl, especially mallards, are natural reservoirs for avian influenza viruses and are also the most resistant to infection. Direct or indirect contact of domestic birds with wild waterfowl is a frequent cause of epizootics. Live bird markets also contributed significantly to the spread of the disease.

Recent research has shown that viruses with low pathogenicity can circulate and become highly virulent after a short period of circulation in domestic bird populations. For example, during the 1983-1984 epidemic in the USA, the A H5N2 virus became very virulent in about six months, with a mortality of 90%. In Italy in 1999-2001, the A H7N1 virus became highly pathogenic within nine months.

Avian influenza is controlled by quarantining affected farms and culling infected or exposed birds. Airborne viruses are highly contagious and can be spread mechanically through equipment, vehicles, food, cages or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially at low temperatures. Strict hygiene measures applied in poultry farms can provide a level of protection.

Without prompt control measures and good monitoring, epidemics can last for years. For example, the H5N2 influenza epidemic that started in Mexico in 1992 progressed to a severe and deadly form and was not controlled until 1995.

The virus goes through mutations

Among the 15 subtypes of avian influenza virus, A H5N1 is of particular interest for several reasons. The virus moves quickly and can take over genes from viruses that infect other animal species. Its ability to cause severe disease in humans with a high mortality rate has been demonstrated in several cases. Birds that survive infection shed the virus for at least 10 days, thus enabling rapid spread of disease.

The H5N1 avian influenza virus, through continuous mutations, has significantly changed its biological and antigenic properties, acquiring the ability to infect humans directly, without an intermediate host, and to produce very severe clinical forms, often fatal, cause.

Transmission routes of avian influenza virus type A H5N1

Bird flu is spread through direct contact between infected birds and healthy birds and through the birds’ contact with objects contaminated with the virus. The virus is found in the respiratory, digestive and other organs of infected birds and can be excreted through secretions from the eyes, nasal passages, oral cavity and droppings.

Excreta, dead chickens and birds carrying the virus, as well as feed, drinking water, coops, farm tools, transport and clothing of farm workers, can spread the disease. Healthy birds can become infected through the respiratory and digestive tracts, writes DSPBV.ro.

The highly dangerous bird flu virus is similar to seasonal flu and can spread in all seasons. However, the flu spreads more easily in the winter and spring because the virus is better able to withstand cold temperatures. Birds of all species and ages can be infected, and epizootics develop rapidly, with mortality up to 100%.

Airborne influenza virus is very sensitive to temperature and can be destroyed in 2-10 minutes at 60-70 ° C. Cooked meat, eggs and other properly cooked poultry products can be eaten without any concern.

In humans, the virus can be transmitted by direct contact with infected birds or by eating undercooked meat.

Bird flu symptoms in birds

Symptoms of avian influenza in birds can vary greatly depending on the type of virus and the species of bird infected. Common symptoms include sudden death, especially in domestic birds, which may die suddenly without other obvious symptoms. Respiratory problems are common, manifesting as shortness of breath, wheezing, coughing and sneezing. Neurological symptoms such as tremors, unsteady movements, and twisting of the head and neck are also common.

Birds may have eye and nasal discharge, with watery or mucous discharge from the eyes and nostrils. Diarrhea, characterized by green or yellow watery stools, is another symptom. Lethargy and lack of energy are common, as is decreased appetite, manifested by loss of interest in food. In chickens and turkeys, the crest and chin may be swollen and discolored, and aubergine spots may appear on the legs, writes ANSVSA.ro.

It is important to remember that not all infected birds will show symptoms. Some birds can be infected and pass the virus to other birds without feeling sick.

Bird flu symptoms in humans

Bird flu symptoms in humans they can range from mild to severe and occur between 2 and 14 days after exposure to the virus. Common symptoms include high fever (over 38°C), heavy cough, often with sputum, severe sore throat, general muscle and joint pain, headache and extreme fatigue.

Other less common symptoms may include diarrhoea, vomiting, nausea, abdominal pain, conjunctivitis (inflammation of the conjunctiva of the eye) and pneumonia.

What is the risk of bird flu spreading?

The global risk of the spread of bird flu remains moderate, according to the World Health Organization (WHO). However, several factors affect this risk.

The type of virus

Human avian influenza (HPAI) viruses are of great concern because they can be highly contagious and can cause serious illness and death in birds and, in some cases, in humans.

Low pathogenic avian influenza (LPAI) viruses are less infectious and rarely cause severe disease in humans.

Geographic distribution

Outbreaks of HPAI avian influenza have been reported in Europe, Asia and North America.

The risk of spread is greater in areas with a high density of domestic and wild birds and in areas with heavy traffic of birds and poultry products.

Climate change and environmental factors

Climate change could affect bird migration and increase contact between wild and domestic birds, increasing the risk of virus transmission.

Environmental factors, such as floods or drought, can concentrate birds in small areas, favoring the spread of the virus.

Ability to lead and control

Countries with effective animal disease surveillance and control systems are better equipped to detect and respond to avian influenza outbreaks.

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