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Introducing the most common types of wet season illness in Thailand

The Land of Smiles has three official seasons: hot, cool, and wet. The wet season (in other words, Thailand’s flu season) begins around mid-May every year, and continues until mid-October when rainfall starts to become less frequent. There are both pros and cons to traveling or living in Thailand during the wet season. Due to the lower number of tourists, it’s usually quieter, cooler, and calmer in most regions. The wet season, however, can also bring additional risks to your health, as mentioned. Here, Pacific Prime Thailand looks at the most common Thailand wet season illnesses to watch out for, and what you can do to avoid them.


Dengue is a mosquito-borne viral infection. It is one of the common diseases in Thailand during the wet season, with higher transmission rates during this time. Transmitted via the bite of infected female mosquitoes (Aedes aegypti and Aedes albopictus) – which thrive in stagnant water – dengue usually causes body aches, fever, headache, and a skin rash with red spots. Worryingly, there’s around a 36 percent chance for this wet season illness to develop into Dengue Hemorrhagic Fever (DHF), which is associated with severe symptoms like:

  • Vomiting
  • Bruising
  • Uncontrolled bleeding
  • High fever
  • Diarrhea
  • Abdominal pain

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Those with severe dengue must seek medical treatment immediately, as complications can be fatal and lead to circulatory system failure.

How to protect yourself from dengue during Thailand’s wet season: We actually discussed dengue prevention in one of our previous blog articles on dengue fever, but here’s a quick recap of the most important precautionary measures people living or traveling in Thailand should be aware of:

  • Get the dengue vaccine
  • Wear loose, long-sleeved clothing
  • Use an insect repellent
  • Remove water containers around your home
  • Consider purchasing an insecticide-treated bed net


Another common disease in Thailand is Pneumonia, which is a wet season illness. Characterized by infection of one/both lungs, people with pneumonia usually experience physical symptoms such as shortage of breath, clammy skin, fever, chills, cough, and shaking. In certain cases, pneumonia can become a side effect of other health conditions – e.g. asthma. While most cases of pneumonia can be treated successfully, it can be fatal if left untreated – especially among young children, the elderly, and those with weakened immune systems.

How to protect yourself from pneumonia during Thailand’s wet season: Pneumonia is highly contagious, so it is important that you try to keep others from getting infected as well. If you’re suffering from any of the above-mentioned symptoms, make sure you see a doctor as soon as possible. Maintaining good personal hygiene is also key – as your hands are in constant contact with different types of bacteria, you should make it a habit to wash them with soap frequently and thoroughly to lower your risk of infection.

Japanese encephalitis

Like Dengue, Japanese encephalitis is also a mosquito-borne illness that can, in severe cases, lead to inflammation of the brain. While the risk of contracting this wet season illness is not very high when compared to the incidence rates of other mosquito-borne illnesses (e.g. dengue), you are at a higher risk if you live or travel to rural areas for a prolonged period of time. In Thailand, the disease is most common in northern areas (e.g. Chiang Mai valley).

People infected with Japanese encephalitis will usually develop the following symptoms:

  • Fever
  • Confusion
  • Vomiting
  • Headache
  • Difficulty moving

In severe cases, swelling can develop around the brain, and result in cognitive/neurological damage.

How to protect yourself from Japanese encephalitis during Thailand’s wet season: The most effective ways of protecting yourself from Japanese encephalitis include preventing mosquito bites (e.g. by using an appropriate insect repellent), and getting the Japanese encephalitis vaccine at least 6 weeks before traveling to a high risk area.


The wet season coincides with flu season in Thailand. This is because people are indoors together more often when it’s raining, which increases the risk of spreading and contracting viruses. The flu is one of the most common diseases in Thailand during the wet season. This is because in the tropics, where the air stays hot all year long, the flu season tends to peak with the heavy monsoon rains

If you have a cold, you will usually experience symptoms like coughing, fever, and sneezing for several days. However, flu symptoms can be more serious – e.g. high fever, body- and headaches, fatigue – and usually lasts longer, too. Although the flu itself is not usually harmful, it can lead to complications among those with certain medical conditions, such as asthma, sinusitis, and bronchitis.

How to protect yourself from the flu during Thailand’s wet season: The best form of protection against the flu is to stay healthy and boost your immunity. Regular exercise and a nutrient-rich diet are therefore key. The flu vaccine is also highly recommended, especially if you’re more at risk of developing medical complications arising from flu.


Last but not least, malaria is another health risk to watch out for – especially during the wet season. While there is no risk in the cities of Bangkok, Chiang Mai, and Pattaya, those traveling to more remote or rural areas should be aware of the presence of infective female Anopheles mosquitoes.

There are five species of human malaria parasites, the most dangerous being Plasmodium falciparum. Characterized by flu-like symptoms (e.g. chills, headache, malaise, fever), those experiencing symptoms should seek medical attention as soon as possible. This is because malaria can lead to severe seizures, mental confusion, coma, and even death.

How to protect yourself from malaria during Thailand’s wet season: Those traveling to malaria-present areas should consider antimalarial medication, and using a mosquito bed net and insect repellent to avoid getting bitten by Anopheles mosquitoes.

Does your expatriate medical insurance cover wet season illness?

Medical treatment for wet season illness can be costly in Thailand, especially if you require hospitalization at top private hospitals, or if complications occur. We therefore recommend obtaining robust expatriate medical insurance with higher annual limits so that you can access the best care without having to worry about paying bank-breakingly expensive hospital bills.

Not only will medical insurance cover your cost of wet illness treatments while in Thailand, but it will also cover a number of other health problems you may face. What’s more, if your plan has vaccination benefits, you can also use it to cover all essential inoculations for Thailand. If you don’t know where to begin in your hunt for medical insurance, you’ve come to the right place!

Whether you’re looking for travel insurance, short term health insurance, or international health insurance, Pacific Prime Thailand can help. As Asia’s leading insurance broker, we have over two decades of experience helping expats understand insurance jargon, compare health insurance, and select the most appropriate plan, which includes a wide range of benefits, such as:

  • Inpatient insurance
  • Outpatient insurance
  • Maternity coverage
  • Dental coverage
  • International health coverage
  • Pre-existing conditions coverage
  • Vision insurance
  • And more!

Contact us to get started today!

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Content Strategist at Pacific Prime Thailand
Jessica Lindeman is a Content Strategist at Pacific Prime. She comes to work every day living and breathing the motto of "simplifying insurance", and injects her unbridled enthusiasm for health and insurance related topics into every article and piece of content she creates for Pacific Prime. When she's not typing away on her keyboard, she's reading poetry, fueling her insatiable wanderlust, getting her coffee fix, and perpetually browsing animal Instagram accounts.