Watch Out for Infectious Diseases
FoundationFlu and cholera are infectious diseases spread by droplets, contact and food; washing hands, wearing masks and getting vaccinated greatly lower the risk.
- Infectious diseases are caused by pathogens such as viruses and bacteria and pass between people.
- They spread in five ways: droplets, contact, food, vectors and blood.
- Flu spreads by droplets; cholera spreads through unsafe food and water.
文體小知識：說明文把知識講得清清楚楚。這一篇教你認識傳染病的成因、五種傳播途徑和預防方法，做個健康小衛士。
§Text Passage
1Why are there a few empty seats in class today? A classmate has caught influenza and is resting at home. Infectious diseases are illnesses caused by pathogens such as viruses and bacteria. They pass from one person to another, so when someone falls ill, everyone nearby must stay on guard.
2Influenza, or flu, is caused by the influenza virus. People with flu have a fever, headache, cough, sore throat, aching muscles and great tiredness. Flu spreads by droplets: when patients cough or sneeze, tiny drops carrying the virus fly into the air, and others may fall ill after breathing them in.
3Cholera is caused by a bacterium called the cholera vibrio and attacks the gut. Patients suffer severe diarrhoea and vomiting and lose large amounts of water; without timely treatment, dehydration can be life-threatening. Cholera spreads mainly through contaminated food and water, so food must be thoroughly cooked and drinking water properly treated.
4Infectious diseases spread in five main ways: droplets, contact, food, vectors and blood. Droplets fly when people cough and sneeze; contact means touching objects carrying germs and then touching the mouth or nose; food transmission means eating unsafe food; vectors such as mosquitoes and flies carry germs to people; blood transmission spreads viruses through infected blood.
5Everyone can help prevent infectious diseases: wash hands properly with soap, wear a mask when ill, receive vaccinations as needed, keep the environment clean, cook food thoroughly and clear stagnant water to stop mosquitoes. With these good habits, germs will find no way in, and both you and your classmates stay healthy.
1Summary 重點摘要
Flu and cholera are infectious diseases spread by droplets, contact and food; washing hands, wearing masks and getting vaccinated greatly lower the risk.
2Vocabulary cards Vocabulary
A disease caused by pathogens that can pass from person to person, such as flu.
Tiny living things that cause illness, such as viruses and bacteria.
A pathogen even smaller than bacteria, such as the flu virus, which can only multiply inside living cells.
A single-celled microbe; some kinds cause illness, such as the cholera vibrio.
Tiny drops spat out when we cough, sneeze or talk; they can carry pathogens.
A living thing that carries pathogens to people, such as mosquitoes that spread dengue fever.
A preparation put into the body so it builds resistance and is protected against a specific disease.
Unusual signs the body shows when ill, such as fever, cough and headache.
A gut disease caused by the cholera vibrio and spread through unsafe food and water.
The body's power to fight germs and keep itself from falling ill.
3Step by step Steps
- Step 1: Know what infectious diseases areInfectious diseases are illnesses caused by pathogens. Pathogens are extremely tiny living things, including viruses and bacteria; our eyes cannot see them, yet they sneak into our bodies and cause trouble. Their greatest feature is that they can pass between people: when one classmate falls ill and no one takes care, others may catch it one after another. Common examples are influenza, chickenpox, hand-foot-mouth disease and cholera. Learning what causes these diseases and how they spread is the first step of protecting ourselves, and an important lesson in how science keeps us healthy.
- Step 2: The causes and symptoms of influenzaInfluenza, or flu, is caused by the influenza virus; when many people catch it at once, an outbreak occurs. People with flu usually have a fever and chills, headache, cough, sore throat, aching muscles and deep tiredness, and they generally need a few days or even a week of rest to recover. Flu differs from an ordinary cold: its symptoms are usually heavier and it is far more contagious, so schools and care homes are the easiest places for outbreaks. Once flu symptoms appear, rest at home and see a doctor with a mask on — protecting yourself and your classmates at the same time.
- Step 3: The causes and symptoms of choleraCholera is caused by a bacterium called the cholera vibrio, which attacks the gut. Patients suddenly suffer severe diarrhoea and vomiting, losing large amounts of water and salt in a short time; without timely treatment, dehydration can cost their lives. Cholera spreads mainly through contaminated water and food and has caused many great epidemics in history. In Hong Kong today, as long as we boil drinking water, cook food thoroughly, keep raw and cooked food apart and keep our hands clean, cholera has very little chance to spread.
- Step 4: The five ways diseases spreadAfter leaving a patient's body, pathogens mainly seek a new host through five routes. First, droplets: people breathe in the drops sprayed out by coughs and sneezes. Second, contact: touching door handles or toys that carry germs, then touching the mouth or nose. Third, food: eating undercooked or contaminated food and water. Fourth, vectors: mosquitoes and flies carry pathogens onto people — for example, mosquitoes spread dengue fever. Fifth, blood: viruses enter another person's body through wounds or shared needles with infected blood.
- Step 5: Personal hygiene stops infectionThe simplest and most effective defence against infectious diseases lies in our own hands. First, wash hands properly with soap, scrubbing for at least twenty seconds, especially before eating, after the toilet and after coming home; do not touch the mouth, nose or eyes before hands are clean. Second, cover the mouth and nose with a tissue or the elbow when coughing or sneezing, and throw used tissues into a lidded bin at once. Third, wear a mask when ill to stop droplets flying, and rest at home. These habits cut off the two great routes of droplets and contact, protecting yourself and others.
- Step 6: Vaccines and a clean environmentBesides personal hygiene there are two more lines of defence. The first is vaccination: vaccines let the body build resistance against a particular pathogen in advance — the seasonal flu vaccine and the chickenpox vaccine, for example — so that even after contact with the germ we do not easily fall ill. The second is environmental hygiene: keep classrooms airy and clean and clean shared objects often; cook food thoroughly and drink boiled water; clear stagnant water so mosquitoes cannot breed. With personal care, vaccines and the environment all handled, pathogens find no opening.
5Worked example Example
Example: Chun of Primary 5 came back to class with flu. He wore no mask, coughed without covering his mouth, and shared a towel with classmates. Three days later five classmates had fevers one after another. How did the germs spread? What preventive measures should the class take?
- Chun coughed without covering his mouth, so droplets carrying the flu virus spread into the air and nearby classmates breathed them in — this is droplet transmission.
- Without a mask, his hands picked up the virus and touched door handles, desks and the shared towel; others touched them and then their mouths or noses — this is contact transmission.
- Immediate measures: sick classmates rest at home until recovered; the whole class washes hands more often; windows stay open for fresh air; desks and handles are cleaned and disinfected.
- Long-term measures: cover coughs and sneezes with a tissue or elbow; do not share personal items such as towels and water bottles; receive the flu vaccine as needed.
- Answer: The flu virus spread by droplets (coughing uncovered, no mask) and by contact (sharing a towel and touching shared objects). Prevention: the sick rest at home, wash hands often, wear masks, cover coughs and sneezes, avoid sharing personal items, keep the classroom airy and clean, and get vaccinated as needed.
6Common mistakes Mistakes
7Quick check Quick check
Q1What causes influenza?
Q2How does cholera mainly spread?
Q3Name one disease spread by a vector.
Q4How long should hand-washing take?
Q5What do vaccines do?
8Recap Recap
- Infectious diseases are caused by pathogens such as viruses and bacteria and pass between people.
- They spread in five ways: droplets, contact, food, vectors and blood.
- Flu spreads by droplets; cholera spreads through unsafe food and water.
- Wash hands often, wear masks and cover sneezes to cut the routes of spread.
- Vaccinate as needed and keep the environment clean — germs find no opening.