Highly pathogenic avian influenza

• Influenza is a zoonotic disease caused by a virus that attacks mainly the upper respiratory tract the nose, throat and bronchi, and rarely also the lungs.
• The infection usually lasts for about a week and is characterized by sudden onset of high fever, myalgia, headache and severe malaise, non-productive cough, sore throat and rhinitis.
• Most people recover within 1-2 weeks without requiring any medical treatment.
• Influenza spreads rapidly around the world in seasonal epidemics, imposing a considerable economic burden in the form of hospital and other health care costs and in lost productivity. In the United States of America, for example, recent estimates put the cost of influenza epidemics to the economy at US$ 71167 billion per year.
• In annual influenza epidemics, 5%-15% of the population are affected with upper respiratory tract infections. Hospitalization and deaths occur mainly in high-risk groups (elderly, chronically ill). Although difficult to assess, these annual epidemics are thought to result in between 3 and 5 million cases of severe illness and between 250 000 and 500 000 deaths every year worldwide. Most deaths currently associated with influenza in industrialized countries occur among the elderly aged over 65 years.
• The currently circulating influenza viruses that cause human disease are divided into two groups: influenza A and B. Influenza A has two subtypes that are important for humans: A(H3N2) and A(H1N1); influenza A(H3N2) is currently associated with most deaths. Influenza viruses are defined by two different protein components, or antigens, on the surface of the virus. They are spike-like features called haemagglutinin (H) and neuraminidase (N) components.
• The genetic makeup of influenza viruses allows frequent minor genetic changes, known as antigenic drift, and these changes require annual reformulation of influenza vaccines.

Three times in the last century, the influenza A viruses have undergone major genetic changes mainly in their H-component resulting in global pandemics and large tolls in terms of both disease and deaths. The most infamous pandemic was Spanish Flu, which affected large parts of the world’s population and is thought to have killed at least 40 million people in 1918-1919. More recently, two other influenza A pandemics have occurred in 1957 (Asian influenza) and in 1968 (Hong Kong influenza) causing significant morbidity and mortality globally. In contrast to current influenza epidemics, these pandemics were associated with severe outcomes also among healthy younger persons; albeit not on such a dramatic scale as the Spanish flu where the death rate was highest among healthy young adults. Most recently, in 1997 and 2003, limited outbreaks of a new influenza subtype A (H5N1) directly transmitted from birds to humans have occurred in Hong Kong Special Administrative Region of China.

Suspect case: Fever (temperature >38°C) and [cough or shortness of breath or difficulty in breathing] with onset of symptoms within the last 10 days in a person who has had one or more of the following epidemiological exposures in the two weeks prior to the onset of symptoms in [Area X] since/during [date Y/date Y to Zb]. The different types of exposure are:

• Close contact (within one metre) with a person who is a suspected, probable or confirmed case;
• Exposure to animals or their remains or environments soiled by their faeces in an area where cases of non-seasonal influenza infections in animals or humans have been suspected or confirmed in the past month;
• Consumption of raw or undercooked animal products in an area where influenza infections in animals or humans have been suspected or confirmed in the past month;
• Close contact with a confirmed influenza-infected animal;
• Handling specimens suspected of containing non-seasonal influenza virus in a laboratory or other environment

Probable case: Any suspected case with either:

• Positive laboratory confirmation of influenza A virus infection, but insufficient laboratory evidence for the subtype; or
• A person dying of an unexplained acute respiratory illness that is considered to be epidemiologically linked to a probable or confirmed case of non-seasonal influenza in a human.

Confirmed case: Laboratory confirmation of recent infection with non-seasonal influenza virus in a person.

Rejected case: A suspected or probable case with a negative test for non-seasonal influenza virus.

The influenza virus is easily passed from person to person through the air by droplets and small particles excreted when infected individuals cough or sneeze. It enters the body through the nose or throat. Symptoms develop between one and later four days. A person suffering from influenza can be infectious from the day before they develop symptoms until seven days afterwards. Disease spreads very quickly among the population, especially in crowded circumstances. Cold and dry weather enables the virus to survive longer outside the body than in other conditions and, as a consequence, seasonal epidemics in temperate areas appear in winter. 

Influenza poses a serious risk for the very young, the elderly and people suffering from medical conditions such as lung diseases, diabetes, cancer, kidney or heart problems, in whom the infection may lead to severe complications of underlying diseases, pneumonia and death.

The reported signs and symptoms of bird flu virus infections in humans have ranged from no symptoms or mild illness [such as eye redness (conjunctivitis) or mild flu-like upper respiratory symptoms], to severe (such as pneumonia requiring hospitalization) and included fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish*, cough, sore throat, runny or stuff nose, muscle or body aches, headaches, fatigue, and shortness of breath or difficulty breathing. Less common signs and symptoms include diarrhea, nausea, vomiting, or seizures.

*Fever may not always be present

Respiratory illness caused by influenza is difficult to distinguish from illness caused by other respiratory pathogens on the basis of symptoms alone. However, during laboratory-confirmed influenza outbreaks, most people seeking medical advice for upper respiratory tract infections are likely to be infected by influenza. Laboratory confirmation will be required between annual influenza epidemics. Rapid diagnostic tests have recently become available that can be used to detect influenza viruses within 30 minutes. Despite the availability of rapid diagnostic tests, the collection of clinical specimens for viral culture remains critical to provide information regarding circulating influenza subtypes and strains. Such information is needed to guide decisions regarding influenza treatment and chemoprophylaxis and to formulate vaccine for the coming year.

For most people, influenza is an upper respiratory tract infection that lasts several days and requires symptomatic treatment only. Within days, the person’s body will eliminate the virus. Antibiotics, such as penicillin, which are designed to kill bacteria, cannot attack the virus. Antibiotics therefore have no role in treating influenza in otherwise healthy people, although they are used to treat complications. Antiviral drugs for influenza are an important adjunct to influenza vaccine for the treatment and prevention of influenza. However, they are not a substitute for vaccination. For several years, four antiviral drugs that act by preventing influenza virus replication have been available. They differ in terms of their pharmacokinetics, side-effects, routes of administration, target age groups, dosages and costs. When taken before infection or during early stage of the disease (within two days of onset of illness), antivirals may help prevent infection and, if infection has already taken hold, their early administration may reduce the duration of symptoms by one or two days. For several years, amantadine and rimantadine were the only antiviral drugs. However, whilst relatively inexpensive, these drugs are effective only against type A influenza, and may be associated with severe adverse effects (including delirium and seizures that occur mostly in elderly persons on higher doses). When used for prophylaxis of pandemic influenza at lower doses, such adverse events are far less likely. In addition, the virus tends to develop resistance to these drugs. A new class of antivirals, the neuraminidase inhibitors, has been developed. Such drugs, zanamivir and oseltamivir, have fewer adverse side-effects (although zanamivir may exacerbate asthma or other chronic lung diseases) and the virus less often develops resistance. However, these drugs are expensive and currently not available for use in many countries. In severe influenza, admission to hospital, intensive care, antibiotic therapy to prevent secondary infection and breathing support may be required.

Vaccination is the principal measure for preventing influenza and reducing the impact of epidemics. Various types of influenza vaccines have been available and used for more than 60 years. They are safe and effective in preventing both mild and severe outcomes of influenza.2 It is recommended that elderly persons, and persons of any age who are considered at high risk for influenza-related complications due to underlying health conditions, should be vaccinated. Among the elderly, vaccination is thought to reduce influenza-related morbidity by 60% and influenzarelated mortality by 70%-80%. Among healthy adults, the vaccine is very effective (70%-90%) in reducing influenza morbidity, and vaccination has been shown to have substantial health-related and economic benefits among this age group. The effectiveness of influenza vaccine depends primarily on the age and immunocompetence of the vaccine recipient and on the degree of similarity between the viruses in the vaccine and those in circulation. Influenza vaccination can reduce both health-care costs and productivity losses associated with influenza illness.3 All current inactivated influenza vaccines contain trace levels of egg protein and should not be used by individuals with egg protein allergies. Constant genetic changes in influenza viruses mean that the vaccines’ virus composition must be adjusted annually to include the most recent circulating influenza A (H3N2), A (H1N1) and influenza B viruses. The WHO Global Influenza Surveillance Network writes the annual vaccine recipe. The network, a partnership of 112 National Influenza Centers in 83 countries, is responsible for monitoring the influenza viruses circulating in humans and rapidly identifying new strains. Based on information collected by the Network, WHO recommends annually a vaccine that targets the three most virulent strains in circulation.

From 2002 to 2022, we have identified ten (10) outbreaks of Highly Pathogenic Avian Influenza (HPAI) in Africa, of which seven (7) are in North Africa, two (2) in West Africa and one (1) in South Africa. These outbreaks have been identified in three (03) countries namely: Egypt, Madagascar and Nigeria. Over the last twenty (20) years, Madagascar has been the most affected country by HPAI in Africa with 1 epidemic (in 2022), i.e. a total of 13,300 cases, including 0 suspected cases, 13,300 confirmed cases and 444 deaths, for a case-fatality rate of 3.3% (444/13,300). The second most affected country has been Egypt with 7 epidemics (in 2006, 2007, 2008, 2009, 2010, 2011 and 2012). These outbreaks resulted in a total of 635 cases, including 0 suspected cases, 635 confirmed cases and 227 deaths, for a case-fatality rate of 35.7% (227/635). In Nigeria, with 2 outbreaks (in 2006 and 2007), there were a total of 8 cases, including 8 suspected cases, 0 confirmed cases and 2 deaths, for a case-fatality rate of 25% (2/8). In sum, over the past two decades, Africa has recorded 13,308 cases, including 8 suspected cases, 13,300 confirmed cases and 446 deaths, for a case-fatality ratio of 3.4% (446/13,308). The main risk factor was exposure to backyard poultry. The response actions undertaken were the organisation of mobile teams to provide medical support to new outbreaks of the disease and the provision of medical care.

No outbreak was recorded since 2013.