Influenza A, H1N1 /2009 (swine flu)

Dr Muhammad Najeeb Durrani, National Surveillance Officer, World Health Organization, Epidemic Investigation Cell, National Institute of Health, Islamabad

2009 H1N1 (sometimes called “swine flu”) is a new influenza virus causing illness in people. This new virus was first detected in people in the Mexico and United States in April 2009. The disease soon within six months spread to all the regions of the world and was confirmed in more than 182 countries. Based on assessment of all available information, and following several expert consultations, on June 11, 2009, the World Health Organization (WHO) declared that a pandemic of 2009 H1N1 flu was underway. This virus is still spreading from person-to-person worldwide, probably in much the same way that regular seasonal influenza viruses spread.

Influenza pandemics must be taken seriously and precisely because of their capacity to spread rapidly to every country in the world. At this stage, effective and essential measures include heightened surveillance, early detection and treatment of cases, and infection control in all health facilities. At the national; level country needs to be better prepared to deal with any situation affecting the masses and provincial Health Departments must strive for achieving a fairly good level of preparedness.

This virus was originally referred to as “swine flu” because laboratory testing showed that many of the genes in the virus were very similar to influenza viruses that normally occur in pigs (swine) in North America. But further study has shown that the 2009 H1N1 is very different from what normally circulates in North American pigs. It has two genes from flu viruses that normally circulate in pigs in Europe and Asia and bird (avian) genes and human genes. Scientists call this a “quadruple reassortant” virus.

2009 H1N1 FLU IN HUMANS

The 2009 H1N1 virus is contagious and is spreading from human to human. Although the 2009 H1N1 virus activity has declined after later October, still the 2009 human illness with 2009 H1N1 virus is ongoing in the world. In fact, the 2009 H1N1 virus is the predominant influenza virus in circulation so far during the 2009-2010 flu season. The United States experienced its first wave of 2009 H1N1 activity in the spring of 2009, followed by a second wave in the fall, with the number of people infected peaking at the end of October.

There are still uncertainties surrounding the rest of this flu season, including the possibility that seasonal influenza viruses will also spread during the winter as they usually do while 2009 H1N1 viruses continue to cause illness. In past pandemics, flu activity has occurred in waves and it’s possible that the world may experience another wave either later in the 2010 winter, or later. In the past, when new viruses have emerged to cause flu pandemics, the new virus has continued to spread among people. Experts believe it’s likely that the new 2009 H1N1 virus will continue to circulate among people for some time, perhaps as typical winter flu.

SPREAD OF THE 2009 H1N1 VIRUS

Spread of the 2009 H1N1 virus is thought to occur in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing, sneezing or talking by people with influenza. Sometimes people may become infected by touching something – such as a surface or object – with flu viruses on it and then touching their mouth or nose.

Getting infected with any influenza virus, including 2009 H1N1, should cause your body to develop immune resistance to that virus so it’s not likely that a person would be infected with the identical influenza virus more than once. (However, people with weakened immune systems might not develop full immunity after infection and might be more likely to get infected with the same influenza virus more than once.) However, it’s also possible that a person could have a positive test result for flu infection more than once in an influenza season. This can occur for two reasons:

A person may be infected with different influenza viruses (for example, the first time with 2009 H1N1 and the second time with a regular seasonal flu virus. Most rapid tests cannot distinguish which influenza virus is responsible for the illness. And,

Influenza tests can occasionally give false positive and false negative results so it’s possible that one of the test results were incorrect. This is more likely to happen when the diagnosis is made with the rapid flu tests.

SIGNS AND SYMPTOMS OF THIS VIRUS

The symptoms of 2009 H1N1 flu virus in people include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people may have vomiting and diarrhea. People may be infected with the flu, including 2009 H1N1 and have respiratory symptoms without a fever. Severe illnesses and deaths have occurred as a result of illness associated with this virus.

Illness with 2009 H1N1 virus has ranged from mild to severe. While most people who have been sick have recovered without needing medical treatment, hospitalizations and deaths from infection with this virus have occurred.

HIGH RISK GROUPS OF SEASONAL FLU AND H1N1 2009 VIRUS

In seasonal flu, certain people are at “high risk” of serious complications. This includes people 65 years and older, children younger than five years old, pregnant women, and people of any age with certain chronic medical conditions. More than 70 percent of adults who have been hospitalized with the 2009 H1N1 virus have had one or more medical conditions previously recognized as placing people at “higher risk” of serious seasonal flu-related complications. This includes pregnancy, diabetes, heart disease, asthma and kidney disease. In one study, fifty-seven percent of children who had been hospitalized as a result of 2009 H1N1 have had one or more “higher risk” medical conditions.

Young children are also at high risk of serious complications from 2009 H1N1, just as they are from seasonal flu. And while people 65 and older are less likely to be infected with 2009 H1N1 flu, if they get sick, they are also at “high risk” of developing serious complications from their illness.

CDC laboratory studies have shown that no children and very few adults younger than 60 years old have existing antibody to the 2009 H1N1 flu virus; however, about one-third of adults older than 60 may have antibodies against this virus. It is unknown how much, if any, protection may be afforded against 2009 H1N1 flu by any existing antibody.

PEOPLE AT RISK OF DEVELOPING COMPLICATIONS DUE TO 2009 H1N1INFECTION

Most people who get the flu (either seasonal or 2009 H1N1) will have mild illness, will not need medical care or antiviral drugs, and will recover in less than two weeks.  Some people, however, are more likely to get flu complications that result in being hospitalized and occasionally result in death. Pneumonia, bronchitis, sinus infections and ear infections are examples of flu-related complications. The flu can also make chronic health problems worse. For example, people with asthma may experience asthma attacks while they have the flu, and people with chronic congestive heart failure may have worsening of this condition that is triggered by the flu.  The list below includes the groups of people more likely to get flu-related complications if they get sick from influenza.

Following are the people at High Risk for Developing Flu-Related Complications:

• Children younger than 5, but especially children younger than 2 years old
• Adults 65 years of age and older
• Pregnant women
• People who have medical conditions including:
• Asthma
• Neurological and neuro-developmental conditions
  [including disorders of the brain, spinal cord, peripheral nerve, and muscle such as cerebral palsy, epilepsy (seizure disorders), stroke, intellectual disability (mental retardation), moderate to severe developmental delay, muscular dystrophy, or spinal cord injury].  
• Chronic lung disease   (such as chronic obstructive pulmonary disease  [COPD] and cystic fibrosis)
• Heart disease (such as congenital heart disease, congestive heart failure and coronary artery disease)  
• Blood disorders (such as sickle cell disease)
• Endocrine disorders (such as diabetes mellitus)
• Kidney disorders
• Liver disorders
• Metabolic disorders (such as inherited metabolic disorders and mitochondrial disorders)
• Weakened immune system due to disease or medication (such as people with HIV or AIDS, or cancer, or those on chronic steroids) 
• People younger than 19 years of age who are receiving long-term aspirin therapy
• In addition, some studies have shown that obese persons (body mass index ?30) and particularly morbidly obese persons (body mass index ?40) are at higher risk, perhaps because they have one of the higher risk conditions above but do not realize it.

COMPARISON OF 2009 H1N1 FLU IN SEVERITY TO SEASONAL FLU

Flu seasons vary in terms of timing, duration and severity. Seasonal influenza can cause mild to severe illness, and at times can lead to death. Each year, in the United States, on average 36,000 people die from flu-related complications and more than 200,000 people are hospitalized from flu-related causes. Of those hospitalized, 20,000 are children younger than 5 years old. More than 90% of deaths and about 60 percent of hospitalization occur in people older than 65.

CDC estimates of the numbers of 2009 H1N1 cases, hospitalizations and deaths are that people younger than 65 years of age are more severely affected by 2009 H1N1 flu relative to people 65 and older compared with seasonal flu. CDC estimates that with 2009 H1N1, approximately 90% of hospitalizations and 88% of estimated deaths from April through December 12, 2009 occurred in people younger than 65 years old. However, because severe illness and deaths have occurred among people 65 and older and because supplies of 2009 H1N1 vaccine have increased dramatically, CDC is now encouraging all people 6 months and older, including people older than 65, to get vaccinated against 2009 H1N1.

Duration of spread of infection from an infected person to others

People infected with seasonal and 2009 H1N1 flu shed virus and may be able to infect others from 1 day before getting sick to 5 to 7 days after. This can be longer in some people, especially children and people with weakened immune systems and in people infected with 2009 H1N1 viruses.

PREVENTION & TREATMENT

How to protect from getting sick

This season, there is a seasonal flu vaccine to protect against seasonal flu viruses and a 2009 H1N1 vaccine to protect against the 2009 H1N1 influenza virus (sometimes called “swine flu”). A flu vaccine is by far the most important step in protecting against flu infection. For information about the 2009 H1N1 vaccines, visit H1N1 Flu Vaccination Resources. For information about seasonal influenza vaccines, visit Preventing Seasonal Flu With Vaccination.

STEPS TO PREVENT THE SPREAD OF GERMS THAT CAUSE RESPIRATORY ILLNESSES:

• Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it.
• Wash your hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub.*
• Avoid touching your eyes, nose or mouth. Germs spread this way.
• Try to avoid close contact with sick people.
• If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.*) Keep away from others as much as possible to keep from making others sick.
• Other important actions that you can take are:
• Follow public health advice regarding school closures, avoiding crowds and other social distancing measures.
• Be prepared in case you get sick and need to stay home for a week or so; a supply of over-the-counter medicines, alcohol-based hand rubs * (for when soap and water are not available), tissues and other related items could help you to avoid the need to make trips out in public while you are sick and contagious.
• What is the best way to keep from spreading the virus through coughing or sneezing?
• If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.*)
• Keep away from others as much as possible. Cover your mouth and nose with a tissue when coughing or sneezing. Put your used tissue in the waste basket. Then, clean your hands, and do so every time you cough or sneeze.

GOING TO WORK IF SOME ONE IN THE HOUSE IS SICK WITH H1N1 INFECTION

Employees who are well but who have an ill family member at home with 2009 H1N1 flu can go to work as usual. These employees should monitor their health every day, and take everyday precautions including covering their coughs and sneezes and washing their hands often with soap and water, especially after they cough or sneeze. If soap and water are not available, they should use an alcohol-based hand rub. If they become ill, they should notify their supervisor and stay home. Employees who have an underlying medical condition or who are pregnant should call their health care provider for advice, because they might need to receive influenza antiviral drugs.

BEST TECHNIQUE FOR WASHING HANDS TO AVOID GETTING THE FLU

Washing your hands often will help protect you from germs. CDC recommends that when you wash your hands — with soap and warm water — that you wash for 15 to 20 seconds. When soap and water are not available, alcohol-based disposable hand wipes or gel sanitizers may be used. You can find them in most supermarkets and drugstores. If using gel, rub your hands until the gel is dry. The gel doesn’t need water to work; the alcohol in it kills the germs on your hands.

STAYING AT HOME IN CASE OF FEVER

Fever can be one of the symptoms of a flu-like illness for many people. A fever is an oral temperature of at least 100 degrees Fahrenheit (37.8 degrees Celsius). Signs of a fever include chills, a flushed appearance, feeling very warm, or sweating. 

To help avoid spreading the flu, if you have a fever, stay at home for at least 24 hours after you no longer have a fever or signs of a fever. However, if you’re taking fever-reducing medicines, you cannot tell if your fever is truly gone. Therefore, when you start to feel better, increase the interval between doses of fever-reducing medicines and continue to monitor your temperature to make sure your fever does not return.

Fever-reducing medicines typically contain acetaminophen (such as Tylenol) or ibuprofen (such as Motrin). These medicines can both help bring fever down and relieve pain. Aspirin (acetylsalicylic acid) should not be given to children or teenagers (anyone aged 18 years and younger) who have flu; this can cause a rare but serious illness called Reye’s syndrome.

EMERGENCY WARNING SIGNS FOR SEEKING MEDICAL CARE URGENTLY

In children:

• Fast breathing or trouble breathing
• Bluish skin color
• Not drinking enough fluids
• Not waking up or not interacting
• Being so irritable that the child does not want to be held
• Flu-like symptoms improve but then return with fever and worse cough
• Fever with a rash

In adults:

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Sudden dizziness
• Confusion
• Severe or persistent vomiting
• Flu-like symptoms that improve but then return with fever and worse cough

ANTI VIRAL MEDICINES

There are drugs your doctor may prescribe for treating both seasonal and 2009 H1N1 called “antiviral drugs.” These drugs can make you better faster and may also prevent serious complications. It’s very important that antiviral drugs be used early to treat flu in people who are very sick (for example people who are in the hospital) and people who are sick with flu and have a greater chance of getting serious flu complications. Other people may also be treated with antiviral drugs by their doctor this season. Most healthy people with flu, however, do not need to be treated with antiviral drugs.

AVOID CONTACTS

CDC recommends that people with 2009 H1N1 flu avoid contact with others as much as possible. If you are sick with flu-like illness, CDC recommends that you stay home for at least 24 hours after your fever is gone except to get medical care or for other necessities. (Your fever should be gone without the use of a fever-reducing medicine.) Stay away from others as much as possible to keep from making others sick.

CONTAMINATION & CLEANING

Duration of the influenza virus that remains viable on objects (such as books and doorknobs)

Studies have shown that influenza virus can survive on environmental surfaces and can infect a person for 2 to 8 hours after being deposited on the surface.

KILLING INFLUENZA VIRUS

Influenza virus is destroyed by heat (167-212°F [75-100°C]). In addition, several chemical germicides, including chlorine, hydrogen peroxide, detergents (soap), iodophors (iodine-based antiseptics), and alcohols are effective against human influenza viruses if used in proper concentration for a sufficient length of time.

If soap and water are not available and alcohol-based products are not allowed, other hand sanitizers that do not contain alcohol may be useful.

SURFACES ARE MOST LIKELY TO BE SOURCES OF CONTAMINATION

Germs can be spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth. Droplets from a cough or sneeze of an infected person move through the air. Germs can be spread when a person touches respiratory droplets from another person on a surface like a desk, for example, and then touches their own eyes, mouth or nose before washing their hands.

WASTE DISPOSAL TO PREVENT THE SPREAD OF INFLUENZA VIRUS

To prevent the spread of influenza virus, it is recommended that tissues and other disposable items used by an infected person be thrown in the trash. Additionally, persons should wash their hands with soap and water after touching used tissues and similar waste.

To prevent the spread of influenza virus it is important to keep surfaces (especially bedside tables, surfaces in the bathroom, kitchen counters and toys for children) clean by wiping them down with a household disinfectant according to directions on the product label.

Linens, eating utensils, and dishes belonging to those who are sick do not need to be cleaned separately, but importantly these items should not be shared without washing thoroughly first.

Linens (such as bed sheets and towels) should be washed by using household laundry soap and tumbled dry on a hot setting. Individuals should avoid “hugging” laundry prior to washing it to prevent contaminating themselves. Individuals should wash their hands with soap and water or alcohol-based hand rub immediately after handling dirty laundry.

Eating utensils should be washed either in a dishwasher or by hand with water and soap.

2009 H1N1 viruses are not spread by food. You cannot get infected with 2009 HIN1 from eating pork or pork products. Eating properly handled and cooked pork products is safe.

DRINKING WATER

Tap water that has been treated by conventional disinfection processes does not likely pose a risk for transmission of influenza viruses. Current drinking water treatment regulations provide a high degree of protection from viruses. No research has been completed on the susceptibility of 2009 H1N1 flu virus to conventional drinking water treatment processes. However, recent studies have demonstrated that free chlorine levels typically used in drinking water treatment are adequate to inactivate highly pathogenic H5N1 avian influenza. It is likely that other influenza viruses such as 2009 H1N1 would also be similarly inactivated by chlorination. To date, there have been no documented human cases of influenza caused by exposure to influenza-contaminated drinking water.

Influenza viruses infect the human upper respiratory tract. There has never been a documented case of influenza virus infection associated with water exposure. Recreational water that has been treated at CDC recommended disinfectant levels does not likely pose a risk for transmission of influenza viruses. No research has been completed on the susceptibility of 2009 H1N1 influenza virus to chlorine and other disinfectants used in swimming pools, spas, water parks, interactive fountains, and other treated recreational venues. However, recent studies have demonstrated that free chlorine levels recommended by CDC (1–3 parts per million [ppm or mg/L] for pools and 2–5 ppm for spas) are adequate to disinfect avian influenza A (H5N1) virus. It is likely that other influenza viruses such as 2009 H1N1 virus would also be similarly disinfected by chlorine. (Source CDC)