Chickenpox is an infectious disease caused by primary infection with varicella zoster virus, a DNA virus of the Alphaherpesvirinae subfamily. The virus infects humans and some other primates and is transmitted by the respiratory route. Symptoms appear 10–21 days after exposure: an itchy vesicular skin rash mainly concentrated on the torso and head, and small ulcers in the oral cavity and tonsil areas. After the rash resolves, the virus remains latent in nerve cell bodies, and can emerge years or decades later to cause shingles.
A classic disease of childhood, the highest prevalence occurs at 4–10 years. Chickenpox is rarely fatal in people with a normal immune system, with around 6,800 deaths worldwide in 2010. Adults tend to experience more severe symptoms than children, and are at higher risk of complications such as pneumonia, hepatitis and encephalitis. Pregnant women and people with a suppressed immune system have the highest risk of serious complications. Chickenpox during the first 28 weeks of gestation can lead to foetal malformations. Infection in adults is usually treated with antiviral drugs, such as aciclovir or valaciclovir, which reduces both symptom severity and the risk of complications. A vaccine is available.
Chikungunya virus is an alphavirus transmitted by Aedes mosquitoes. The disease can cause severe joint pain, sometimes lasting for several months. Outbreaks have occurred across Africa, Asia and India, and in 2013–14, in South America and the Caribbean.
Credit: A2-33 (8 December 2013)
7 April: The outbreak of Ebola haemorrhagic fever (virus pictured) in West Africa continues; there have been over 175 suspected cases including 105 deaths in Guinea, Liberia and Mali. WHO
27 March: South-east Asia becomes the fourth of the six WHO regions to be certified free from poliomyelitis. GPEI
21 March: The ongoing outbreak of poliomyelitis in Syria spreads to Iraq, in the first case there since 2000. WHO
19 March: A meta-analysis of over 29,000 patients hospitalised with H1N1 influenza during the 2009–10 pandemic shows that neuraminidase inhibitors reduced mortality in adults. Lancet Resp Med
14 March: The outbreak of chikungunya continues with 12,000 probable cases across French Guyana and ten Caribbean countries. ECDC
12 March: The Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak continues, with three cases in Saudi Arabia and the United Arab Emirates reported during March; since the outbreak started in September 2012, there have been 189 cases with 82 deaths. WHO
8 March: H7N9 avian influenza outbreak continues, with 13 cases reported in China during March. WHO
6 March: A preliminary trial in 12 HIV-positive people shows that genetically engineering the host's own T cells to express the HIV-resistant CCR5-Δ32 mutation (CCR5 pictured) is safe and feasible; the modified T cells persist several months and appear protected from infection. BBC
3 March: A viable Pithovirus specimen (pictured), the largest nucleocytoplasmic large DNA virus yet found, is discovered in 30,000-year-old samples of frozen tundra. Nature
1 March: A bomb attack kills at least 11 polio vaccine workers in north-west Pakistan; more than 40 polio vaccinators have been killed in the country since December 2012. BBC
24 February: A novel polio-like paralytic syndrome, possibly associated with enterovirus 68, has been reported in 20 people in California. BBC
19 February: A study in Britain and the Isle of Man suggests honey bees might be transmitting the deformed wing virus to wild bumblebees. BBC