All You Need to Know About Infections During the Monsoon Season!

With monsoons around the corner, here is all that you need to know about infections that are more common during the monsoon season! Monsoons not only turn the city vibrant with the colourful umbrellas that were sleeping in a corner during the rest of the year, but the monsoon rains are also a harbinger of infections. Infections during the monsoon season are typically droplet-borne, vector (arthropod)-borne or water-borne.

Droplet Infections

The commonest droplet-borne infections are upper and lower respiratory tract infections, caused by an array of respiratory viruses such as rhinovirus, influenza, SARS-CoV-2 and respiratory syncytial virus. These are transmitted via large droplets that escape the nostrils and the mouth while coughing and sneezing.

• Influenza Virus:

  Human influenza viruses A and B are notorious for causing seasonal epidemics each year. Flu begins with a sore throat, cough and runny nose along with high fever that leaves you extremely tired. Vulnerable people, such as those in the extremes of age, immunocompromised, obese patients and those with underlying medical conditions such as heart disease, lung disease, liver or kidney dysfunction, have higher fatality rates compared to the general population. Plenty of oral fluids, rest and paracetamol are all that are required for an apparently immunocompetent host. However, if there is breathing difficulty, a severe cough or light-headedness, or any of the health conditions listed above, inpatient care is required. Oseltamivir, an antiviral medication, is often prescribed to reduce symptom duration and severity, especially within 48 hours of symptom onset. Annual vaccinations against influenza can prevent and also reduce the severity of these infections.

• SARS-CoV-2:

  Similar to flu, this virus is also transmitted via droplets. Most of the current circulating strains are subvariants of Omicron. It invariably causes mild disease in immunocompetent hosts. However, those with medical conditions, unvaccinated hosts and immunocompromised patients are at risk of severe disease. Remdesivir in those with mild disease with risk factors or those with moderate disease is recommended. COVID-19 vaccinations have helped to a great extent in the control of the recent pandemic.

Following basic cough etiquette such as covering one’s mouth and nose while coughing or sneezing, and avoiding travel by public transport and limiting visits to crowded places, can dramatically control transmission of the above respiratory viral infection during periods of outbreak.

Vector-Borne Infections:

The next set of infections that come with the rain are mosquito-borne, such as malaria, dengue and chikungunya. Unlike the flu, these are noncommunicable. These are identified with blood tests as they cause overlapping symptoms and signs.

• Dengue:

  • Caused by the dengue virus (DENV 1-4), which belongs to the Flavivirus group.
  • Infection with one serotype confers lifelong immunity to that serotype but not to others.
  • Subsequent infection with a different serotype increases risk of severe dengue due to antibody-dependent enhancement (ADE).
  • Transmitted by Aedes aegypti and Aedes albopictus.
  • Incubation Period: 4-7 days.
  • Febrile Phase (2-7 days): High fever, myalgia, retro-orbital pain and rash.
  • Critical Phase (Days 3-7): Patient can develop features of plasma leak.
  • Warning Signs in Dengue: Persistent vomiting, severe abdominal pain, mucosal bleeding, lethargy, hepatomegaly, increased haematocrit or rapid fall in platelets.
  • Diagnosis: Ns1Ag (first 5 days, early detection), dengue IgM (after day 5), dengue RT-PCR is highly specific.
  • Adequate hydration is the key to successful treatment. Transfusion of blood products may help in a select population.

• Malaria:

  • Malaria is a vector-borne protozoal infection caused by Plasmodium species and transmitted by female Anopheles mosquitoes.
  • WHO estimated over 240 million cases and 6,00,000 deaths in 2023.
  • Uncomplicated Malaria: Fever with chills, sweat, headache, myalgias and vomiting.
  • Complicated Malaria: Altered mentation, severe anaemia, renal failure, hypoglycaemia, ARDS, acidosis and shock with high parasitemia.
  • Diagnosis: QBC, microscopy and peripheral smear or rapid diagnostic kits (RDTs). Avoiding water stagnation and using repellents and mosquito nets are some of the key steps in preventing these infections.
  • Treatment: Chloroquine, artemisinin-based combinations. Primaquine (15 mg) single dose for falciparum to reduce transmission and at 1 mg/kg for 7 days for P.vivax to prevent relapse.

• Chikungunya:

  • Chikungunya is caused by an alphavirus and its transmission is mainly through mosquito bites (Aedes aegypti and Aedes albopictus mosquitoes).
  • Fever, polyarthralgia and rash are the typical clinical features.
  • Post-viral arthropathy with persistent joint pain and morning stiffness occurs in the chronic phase.
  • Neurological manifestations such as meningoencephalitis, Guillain-Barre syndrome, optic neuritis, myocarditis and neonatal transmission are some of the atypical and severe manifestations.
  • RT-PCR detects viral RNA during the first week of illness, while chikungunya IgM is usually detectable from day 5 onwards.
  • No specific antivirals are available for treatment. Paracetamol, NSAIDs (after ruling out dengue), hydration and rest are advised for management of the acute phase, while NSAIDs or short courses of corticosteroids are useful in the chronic phases.

Use of long sleeves and pants, mosquito repellents and mosquito nets, and preventing water stagnation are crucial to prevent the above infections.

Water-Borne Infections:

The last group of infections are caused by contaminated food and water such as acute gastroenteritis and viral hepatitis.

• Acute Gastroenteritis

  This presents with vomiting, diarrhoea and crampy abdominal pain with or without fever. This condition is caused by viruses such as norovirus, rotavirus, adenovirus, etc. and bacteria such as Salmonella, Shigella and Campylobacter. Viral gastroenteritis is usually self-limiting and does not require antibiotics, but bacterial diarrhoeas are treated with antibiotics and can have devastating complications such as renal failure.

• Viral Hepatitis

  This is caused by the hepatitis A or E virus and manifests as fever with prodromal symptoms such as fatigue and malaise. As the fever resolves, yellowish discolouration of eyes and skin called jaundice sets in. This disease is diagnosed through blood tests called serologies. Treatment of viral hepatitis is usually supportive.

The best way to prevent these infections is by using proper handwashing techniques, practising good personal hygiene and avoiding consumption of raw food items from roadside eateries. Vaccinations against viral hepatitis also provide benefits.

Follow these simple steps to keep yourselves away from these menacing infections and enjoy the rain by your window with a hot cup of tea! After all, unexpected rains in Chennai are not a rarity anymore!

Dr Sowmya Sridharan
Consultant Infectious Disease,
Kauvery Hospital, Chennai